Showing posts with label ebooks / Notes. Show all posts
Showing posts with label ebooks / Notes. Show all posts

Oct 8, 2010

Google Instant search now in India: a recent tweak to Google search's interface, is now accessible through Google.co.in.

Google Instant search now in India

Google Instant, a recent tweak to Google search's interface, is now accessible through Google.co.in.

Google Instant search was launched on September 8, 2010. Google Instant's three core features include dynamic results, autocomplete predictions and scroll-to-search functionality. Google Instant's combined interface and infrastructure enhancement helps deliver search results quickly, and according to Google, helps save 2 to 5 seconds on a typical search query.
Related News

In the past month since Google Instant has been launched, Google Instant now powers Google Books, Videos, Blogs and Updates. Google Instant also supports keyboard shortcuts to help navigate through search results, according to Google.

Google also revealed certain findings about Google Instant and how people are using the new search feature. After enabling Google Instant, within two weeks, people are adjusting to the new search experience and sifting through their search queries without hitting enter or clicking search.

Google has also seen 7-percent increase in on-the-fly search query editing attributed to Google Instant search. Google has also seen an increased amount of search queries entered into Google's homepage after enabling Google Instant -- since it doesn't work on Google Toolbars on Web browsers or the Google Chrome Omnibox.

Apr 16, 2009

Computer Networks Interview Questions

Computer Networks Interview Questions

1. What are 10Base2, 10Base5 and 10BaseT Ethernet LANs

10Base2—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 100
meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with 5 continuous segments not exceeding 100
meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling and twisted pair cabling.

2. What is the difference between an unspecified passive open and a fully specified passive open

An unspecified passive open has the server waiting for a connection request from a client. A fully specified passive open has the server waiting for a connection from a
specific client.

3. Explain the function of Transmission Control Block
A TCB is a complex data structure that contains a considerable amount of information about each connection.

4. What is a Management Information Base (MIB)

A Management Information Base is part of every SNMP-managed device. Each SNMP agent has the MIB database that contains information about the device's status, its
performance, connections, and configuration. The MIB is queried by SNMP.

5. What is anonymous FTP and why would you use it

Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP uses a login called anonymous or guest, with the
password usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on the host without having
to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas an anonymous user can access.

6. What is a pseudo tty

A pseudo tty or false terminal enables external machines to connect through Telnet or rlogin. Without a pseudo tty, no connection can take place.

7. What is REX

What advantage does REX offer other similar utilities

8. What does the Mount protocol do

The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message is sent to the client from the server after reception
of a client's request.

9. What is External Data Representation

External Data Representation is a method of encoding data within an RPC message, used to ensure that the data is not system-dependent.

10. What is the Network Time Protocol ?

11. BOOTP helps a diskless workstation boot. How does it get a message to the network looking for its IP address and the location of its operating system boot files
BOOTP sends a UDP message with a subnetwork broadcast address and waits for a reply from a server that gives it the IP address. The same message might contain the
name of the machine that has the boot files on it. If the boot image location is not specified, the workstation sends another UDP message to query the server.

12. What is a DNS resource record

A resource record is an entry in a name server's database. There are several types of resource records used, including name-to-address resolution information. Resource
records are maintained as ASCII files.

13. What protocol is used by DNS name servers

DNS uses UDP for communication between servers. It is a better choice than TCP because of the improved speed a connectionless protocol offers. Of course,
transmission reliability suffers with UDP.

14. What is the difference between interior and exterior neighbor gateways

Interior gateways connect LANs of one organization, whereas exterior gateways connect the organization to the outside world.

15. What is the HELLO protocol used for

The HELLO protocol uses time instead of distance to determine optimal routing. It is an alternative to the Routing Information Protocol.

16. What are the advantages and disadvantages of the three types of routing tables

The three types of routing tables are fixed, dynamic, and fixed central. The fixed table must be manually modified every time there is a change. A dynamic table changes its information based on network traffic, reducing the amount of manual maintenance. A fixed central table lets a manager modify only one table, which is then read by other devices. The fixed central table reduces the need to update each machine's table, as with the fixed table. Usually a dynamic table causes the fewest problems for a network administrator, although the table's contents can change without the administrator being aware of the change.

17. What is a TCP connection table

18. What is source route

It is a sequence of IP addresses identifying the route a datagram must follow. A source route may optionally be included in an IP datagram header.

19. What is RIP (Routing Information Protocol)

It is a simple protocol used to exchange information between the routers.

20. What is SLIP (Serial Line Interface Protocol)

It is a very simple protocol used for transmission of IP datagrams across a serial line.

21. What is Proxy ARP

It is using a router to answer ARP requests. This will be done when the originating host believes that a destination is local, when in fact is lies beyond router.

22. What is OSPF

It is an Internet routing protocol that scales well, can route traffic along multiple paths, and uses knowledge of an Internet's topology to make accurate routing decisions.

23. What is Kerberos

It is an authentication service developed at the Massachusetts Institute of Technology. Kerberos uses encryption to prevent intruders from discovering passwords and
gaining unauthorized access to files.

24. What is a Multi-homed Host

It is a host that has a multiple network interfaces and that requires multiple IP addresses is called as a Multi-homed
Host.

25. What is NVT (Network Virtual Terminal)

It is a set of rules defining a very simple virtual terminal interaction. The NVT is used in the start of a Telnet session.

26. What is Gateway-to-Gateway protocol

It is a protocol formerly used to exchange routing information between Internet core routers.

27. What is BGP (Border Gateway Protocol)

It is a protocol used to advertise the set of networks that can be reached with in an autonomous system. BGP enables this information to be shared with the autonomous
system. This is newer than EGP (Exterior Gateway Protocol).

28. What is autonomous system

It is a collection of routers under the control of a single administrative authority and that uses a common Interior Gateway Protocol.

29. What is EGP (Exterior Gateway Protocol)

It is the protocol the routers in neighboring autonomous systems use to identify the set of networks that can be reached within or via each autonomous system.

30. What is IGP (Interior Gateway Protocol)

It is any routing protocol used within an autonomous system.

31. What is Mail Gateway

It is a system that performs a protocol translation between different electronic mail delivery protocols.

32. What is wide-mouth frog

Wide-mouth frog is the simplest known key distribution center (KDC) authentication protocol.

33. What are Digrams and Trigrams

The most common two letter combinations are called as digrams. e.g. th, in, er, re and an. The most common three letter combinations are called as trigrams. e.g. the, ing, and, and ion.

34. What is silly window syndrome

It is a problem that can ruin TCP performance. This problem occurs when data are passed to the sending TCP entity in large blocks, but an interactive application on the receiving side reads 1 byte at a time.

35. What is region

When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.

36. What is multicast routing

Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.

37. What is traffic shaping

One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop
method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

38. What is packet filter

Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting
some criterion are forwarded normally. Those that fail the test are dropped.

39. What is virtual path

Along any transmission path from a given source to a given destination, a group of virtual circuits can be grouped together into what is called path.

40. What is virtual channel

Virtual channel is normally a connection from one source to one destination, although multicast connections are also permitted. The other name for virtual channel is virtual circuit.

41. What is logical link control

One of two sublayers of the data link layer of OSI reference model, as defined by the IEEE 802 standard. This sublayer is responsible for maintaining the link between computers when they are sending data across the physical network connection.

42. Why should you care about the OSI Reference Model

It provides a framework for discussing network operations and design.

43. What is the difference between routable and non- routable protocols

Routable protocols can work with a router and can be used to build large networks. Non-Routable protocols are designed to work on small, local networks and cannot be used with a router

44. What is MAU

In token Ring , hub is called Multistation Access Unit(MAU).

45. Explain 5-4-3 rule

In a Ethernet network, between any two points on the network, there can be no more than five network segments or four repeaters, and of those five segments only three of segments can be populated.

46. What is the difference between TFTP and FTP application layer protocols

The Trivial File Transfer Protocol (TFTP) allows a local host to obtain files from a remote host but does not provide reliability or security. It uses the fundamental packet delivery services offered by UDP. The File Transfer Protocol (FTP) is the standard mechanism provided by TCP / IP for copying a file from one host to another. It uses the services offered by TCP and so is reliable and secure. It establishes two connections (virtual circuits) between the hosts, one for data transfer and another for control information.

47. What is the range of addresses in the classes of internet addresses

Class A 0.0.0.0 - 127.255.255.255
Class B 128.0.0.0 - 191.255.255.255
Class C 192.0.0.0 - 223.255.255.255
Class D 224.0.0.0 - 239.255.255.255
Class E 240.0.0.0 - 247.255.255.255

48. What is the minimum and maximum length of the header in the TCP segment and IP datagram

The header should have a minimum length of 20 bytes and can have a maximum length of 60 bytes.

49. What is difference between ARP and RARP

The address resolution protocol (ARP) is used to associate the 32 bit IP address with the 48 bit physical address, used by a host or a router to find the physical address of another host on its network by sending a ARP query packet that includes the IP address of the receiver. The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

50. What is ICMP

ICMP is Internet Control Message Protocol, a network layer protocol of the TCP/IP suite used by hosts and gateways to send notification of datagram problems back to the sender. It uses the echo test / reply to test whether a destination is reachable and responding. It also handles both control and error messages.

51. What are the data units at different layers of the TCP / IP protocol suite

The data unit created at the application layer is called a message, at the transport layer the data unit created is called either a segment or an user datagram, at the network layer the data unit created is called the datagram, at the data link layer the datagram is encapsulated in to a frame and finally transmitted as signals along the transmission media.

52. What is Project 802

It is a project started by IEEE to set standards that enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN protocols.
It consists of the following: 802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols. 802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs. Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product
being used. The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5). 802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.

53. What is Bandwidth

Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth.

54. Difference between bit rate and baud rate.

Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent
those bits. baud rate = bit rate / N
where N is no-of-bits represented by each signal shift.

55. What is MAC address

The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

56. What is attenuation

The degeneration of a signal over distance on a network cable is called attenuation.

57. What is cladding

A layer of a glass surrounding the center fiber of glass inside a fiber-optic cable.

58. What is RAID

A method for providing fault tolerance by using multiple hard disk drives.

59. What is NETBIOS and NETBEUI
NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote computer and it hides the networking hardware from applications. NETBEUI is NetBIOS extended user interface. A transport protocol designed by microsoft and IBM for the use on small subnets.

60. What is redirector

Redirector is software that intercepts file or prints I/O requests and translates them into network requests. This comes under presentation layer.

61. What is Beaconing

The process that allows a network to self-repair networks problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.

62. What is terminal emulation, in which layer it comes

Telnet is also called as terminal emulation. It belongs to application layer.

63. What is frame relay, in which layer it comes

Frame relay is a packet switching technology. It will operate in the data link layer.

64. What do you meant by "triple X" in Networks

The function of PAD (Packet Assembler Disassembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between hte PAD and the network, called X.29. Together, these three recommendations are often called "triple X"

65. What is SAP

Series of interface points that allow other computers to communicate with the other layers of network protocol stack.

66. What is subnet

A generic term for section of a large networks usually separated by a bridge or router.

67. What is Brouter

Hybrid devices that combine the features of both bridges and routers.

68. How Gateway is different from Routers

A gateway operates at the upper levels of the OSI model and translates information between two completely different network architectures or data formats.

69. What are the different type of networking / internetworking devices

Repeater: Also called a regenerator, it is an electronic device that operates only at physical layer. It receives the signal in the network before it becomes weak, regenerates the original bit pattern and puts the refreshed copy back in to the link.
Bridges: These operate both in the physical and data link layers of LANs of same type. They divide a larger network in to smaller segments. They contain logic that allow them to keep the traffic for each segment separate and thus are repeaters that relay a frame only the side of the segment containing the intended recipent and control congestion.
Routers: They relay packets among multiple interconnected networks (i.e. LANs of different type). They operate in the physical, data link and network layers. They contain software that enable them to determine which of the several possible paths is the best for a particular transmission. Gateways:
They relay packets among networks that have different protocols (e.g. between a LAN and a WAN). They accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it. They operate in all seven layers of the OSI model.

70. What is mesh network

A network in which there are multiple network links between computers to provide multiple paths for data to travel.

71. What is passive topology

When the computers on the network simply listen and receive the signal, they are referred to as passive because they don’t amplify the signal in any way. Example for passive topology - linear bus.

72. What are the important topologies for networks

BUS topology:
In this each computer is directly connected to primary network cable in a single line. Advantages:
Inexpensive, easy to install, simple to understand, easy to extend. STAR topology:
In this all computers are connected using a central hub.

Advantages:

Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physical problems. RING topology:
In this all computers are connected in loop.
Advantages:
All computers have equal access to network media, installation can be simple, and signal does not degrade as much as in other topologies because each computer
regenerates it.

73. What are major types of networks and explain

Server-based network
Peer-to-peer network
Peer-to-peer network, computers can act as both servers sharing resources and as clients using the resources. Server-based networks provide centralized control of network resources and rely on server computers to provide security and network administration

74. What is Protocol Data Unit

The data unit in the LLC level is called the protocol data unit (PDU). The PDU contains of four fields a destination service access point (DSAP), a source service access point (SSAP), a control field and an information field. DSAP, SSAP are addresses used by the LLC to identify the protocol stacks on the receiving and sending machines that are generating and using the data. The control field specifies whether the PDU frame is a information frame (I frame) or a supervisory frame (S - frame) or a unnumbered frame (U - frame).

75. What is difference between baseband and broadband transmission

In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

76. What are the possible ways of data exchange

(i) Simplex (ii) Half-duplex (iii) Full-duplex.

77. What are the types of Transmission media

Signals are usually transmitted over some transmission media that are broadly classified in to two categories. Guided Media:
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light. Unguided Media:
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.

78. What is point-to-point protocol

A communications protocol used to connect computers to remote networking services including Internet service providers.

79. What are the two types of transmission technology available

(i) Broadcast and (ii) point-to-point

80. Difference between the communication and transmission.

Transmission is a physical movement of information and concern issues like bit polarity, synchronization, clock etc. Communication means the meaning full exchange of information between two communication media.

PC Hardware Troubleshooting Tips

PC Hardware Troubleshooting Tips

First, of course, you need to check the stupid stuff. You'd probably be amazed how many "problems" are solved by connecting the cables, or turning on the power switch that you swear you just did. Beyond that, double-check the snugness of your connections—jiggling in a new add-in card or screwing in a cable connection can (and often does) make a difference. You may even want to check the integrity of your cables and connectors. I once solved a baffling SCSI problem by noticing that one of the pins in a miniature 50-pin SCSI-II connector was bent. I had mistakenly presumed, prior to that, that a bent pin would have prevented me from making a connection at all, but it didn't. Unfortunately, as a result, I wasted several hours on something that could've taken two minutes.

Finally, whenever you install something new, whether it's more memory, a new drive, a plug-in card or what-have-you, and something doesn't work, it's more than likely because you made a mistake somewhere in the installation process. Step back through the process again, double- and triple-check your connections, and then try one more time. In the case of RAM that doesn't work or isn't recognized, it could be an incompatibility with the specific manufacturer of the RAM and your motherboard, so see if you can try a different brand before you give up hope. Finally, in some instances installing something new causes a conflict with something else--which is what the rest of this article is all about.

Driver Dilemmas

Once you're past the basics, it’s on to step two. As long as your computer boots, then there's a good chance the problem is related to missing, damaged, incompatible or improperly installed driver software, otherwise known simply as drivers. (If your PC doesn't start up, you may want to create a boot floppy disk—see "How to Create a 'Real' Windows 95 (or 98 or ME) Boot Disk" for more. In addition, you should check out the "PC Startup Troubleshooting Tips" article for more.)

Virtually every piece of hardware located inside or connected externally to your PC requires a driver to communicate and function with the operating system, applications, and other hardware components in your machine. Drivers essentially translate messages back and forth between the hardware in question and the operating system, thereby allowing your computer system to work as a unified whole (at least, in theory). The truth is, though appearances may suggest otherwise, any computer system is actually made up of a bunch of specialized pieces that don't speak the "native language" of other components and, therefore, require a great deal of translation to communicate and work effectively with them. When any of these various levels of translation break down, well, that's when you get problems.

The Device Manager is Your Friend

If you're running Windows 95, 98, or ME, your first stop after the computer finishes the startup process should be the Device Manager, a piece of operating system software that helps you manage the various pieces of your PC. You can get to the Device Manager in several different ways: the two easiest are right-clicking on the My Computer icon on your desktop and selecting Properties from the context menu that pops up when you do this, or by going to the Start menu, going up to Settings, selecting Control Panel from the list of choices and then double-clicking on the System control panel. Either way, you’ll be presented with a tabbed dialog box; click on the tab that says Device Manager, and you’re there.

The first thing to look for is a yellow exclamation point or red international no sign (you know, the circle with the slash through it) next to one of your devices. You may need to click on all the little plus signs next to each category of devices to see the full outline-like list of everything in your computer. If you see the yellow or red symbol, you know something is amiss. My first suggestion is to highlight the offending device and click on the Remove button. What this does is essentially erase the driver software associated with the device as well as references to it within the Windows 95/98/ME Registry. (The Registry tracks all the hardware and software you install, the preferences you set for each, as well as lots of other stuff). The fancy term for this is "logically" removing the device because, even though it may still be physically attached, the computer no longer has any record of its presence.

Next, you should restart your computer, let Windows' Plug-and-Play feature "find" the device again, and redo the driver installation process by either using the driver suggestions that Windows finds and makes or clicking on the Have Disk button and using the installer disks that came with the device. (If both options are possible, I’d go with the disks that came with the hardware—unless you’re sure they are an older version.) If the computer doesn’t find the device, then I would suspect the connections or the device itself. Buy another cable, unplug and re-plug the connectors, remove and then physically reinstall any new plug-in cards or do whatever you have to to ensure that the connection is solid. Once you’ve done that, you’ll find that many times, simply reinstalling the drivers solves the problem.

Other times the problem is due to an older version of a driver conflicting with something else on your system. It’s always a good idea to check for and get the latest versions of drivers that your PC needs. Check the manufacturer’s web site first and if you can’t find the driver, or drivers, there (or if the company is no longer in business), try searching for it at one of the web’s driver repositories, such as The Driver Zone, WinDrivers.Com, WinFiles, or Frank Condron's World o' Windows. If you're running Windows 98 or Windows ME, you may also be able to get a new driver for your hardware via the Windows Update feature off the Start menu.

If you find and download a new driver version, you can often update the driver by clicking on the device listing in the Device Manager, clicking on Properties, selecting the Driver Tab and then clicking on the Update Driver button. From there, depending on what version of Windows you’re using (the original Win95A, the revised Win95B, Win98, or Windows ME), you’ll either need to manually find where the file is located on your hard disk, and then select it, or the computer will attempt to find it for you. Either way, once the correct file is found, you initiate the update process by simply clicking a button.

Some driver updates force you to create new floppy disks, which you then use to update the driver. Frankly, though it’s more work initially, this is a good solution in the long run, I think, because if you ever have to completely reinstall Windows (such as, when you buy yourself a big new hard drive), you’ll generally want to have copies of your drivers on floppies anyway.

Mind your Ps and IRQs

Finally, if that still doesn’t work, you may need to futz with the dreaded IRQs, or Interrupt Requests. Most hardware devices on your computer need attention from the processor on a fairly regular basis (to check their status) and the mechanism for doing that is called Interrupt Requests (because the device politely asks the processor to interrupt what it’s doing at the time and give it some attention—well, sort of). Because of the need to maintain compatibility with older hardware, today’s PCs are still limited to 16 IRQs (numbered 0-15), which is turning out to be a fairly big problem on many newer, well-equipped computers (read one of my InfoWorld Electric "Plugged In" columns to learn more on the subject).

The general principle with IRQ troubleshooting is that two devices cannot typically share an IRQ (an important exception is with some PCI-based add-in cards), and if they try to, one or sometimes neither of the devices will work properly. If you find that you have an IRQ conflict, where two ISA cards or other non-PCI devices are trying to use the same IRQ, you’ll need to change the settings on one of the devices to an open IRQ. The problem is, not every device is able to use every IRQ, so even though you have other IRQs available, the problem device may be incapable of using one of the open IRQs. If that’s the case, you may need to move another device using one of the IRQs that the problem hardware does work with first, and then free up an IRQ for the problem hardware. So, for example, if IRQ 8 is open but you have a SCSI card that only works with IRQs 9 or 11, you may first need to move whatever’s on 11 to 8, and then set the SCSI card to IRQ 11. Unfortunately, this can sometimes lead to an infuriating puzzle game where you try to match devices with your IRQs.

To find out what IRQs are in use by your computer, double click the computer icon at the top of the Device Manager. You’ll see a new window pop up that shows which devices are using which IRQs. Unfortunately it doesn’t leave a blank for any IRQs that are not in use, so if you need to find an available IRQ you’ll have to look close, count the numbers and see if any are missing. If a number between 0 and 15 is missing, that means that particular IRQ is available.

Some older plug-in cards require you to change the IRQs by setting tiny DIP switches on the card itself, or via a dedicated configuration utility. Most newer Plug-and-Play cards can be changed via Windows 95 or Windows 98. To do so, go to the Device Manager, highlight the product in question, click on the Properties button and then go to Resources Tab. Generally, you’ll have to deselect the Use Automatic Settings button to make any changes. Most devices offer several Basic Configuration choices, which is what you should try first. These are different combinations of IRQs, memory ranges, and I/O ranges. All you typically need to worry about is the IRQ. Some devices also let you adjust these parameters individually by clicking the Change Settings button.

Thankfully, you rarely have to worry about IRQ problems if you’re using Windows 95, 98 or ME because they all do a pretty good job of automatically fixing them before they arise. In fact, this is one of their most important, yet little discussed improvements over Windows 3.1. Unfortunately, Windows 3.0 and 3.1 users still have to worry about this kind of stuff on a semi-regular basis. The problem is not unheard of under Windows 95, 98 or ME, however (I ran into it myself), which is why I’ve included it here.

The End

These tips won’t solve all the hardware problems you may run into, but they should solve a good number of them. The important thing to remember when doing any troubleshooting is that computers really are logical devices and there’s always a logical reason for why something isn’t working. Discovering what that reason is and then applying the right solution isn’t always easy (or intuitive), but if you think about the problem logically and work through it step-by-step, there’s a good chance you’ll be able to solve it on your own. And, if worse comes to worse, you can always just nuke everything and start over (see "Starting Over: Repartitioning, Reformatting and Reinstalling" for more on exactly how to do that). Good luck!

Apr 15, 2009

Share Files Using Encrypting File System

Share Files Using Encrypting File System

Encrypting File System File Sharing

Windows XP's EFS supports file sharing between multiple users on a single file. This provides an opportunity for data recovery by adding additional users to an encrypted file. Although the use of additional users cannot be enforced through policy or other means, it is a useful and easy method for enabling recovery of encrypted files by multiple users without actually using groups, and without sharing private keys between users.

Once a file has been initially encrypted, file sharing is enabled through a new button in the user interface (UI). A file must be encrypted first and then saved before additional users may be added. After selecting the Advanced Properties of an encrypted file, a user may be added by selecting the Details button. Individual users may add other users (not groups) from the local machine or from the Active Directory, provided the user has a valid certificate for EFS.

Enabling EFS file sharing

Sharing encrypted files using EFS has been supported since Windows 2000 through Win32 application program interfaces, but EFS has not been exposed in the Windows Explorer User Interface until the development of the Windows XP Professional.

How to encrypt a file for multiple users?

* Open Windows Explorer and select the file you want to encrypt
* Right-click the chosen file and select Properties from the context menu.
* Select the Advanced button to enable EFS.
* Encrypt the file by selecting the Encrypt contents to secure data check box and Click OK

* If this is the first time this file or folder has been encrypted, a dialog box will appear asking if you would like to encrypt the file only or the folder.
* Select the appropriate choice and click OK. This will return you to the original dialog box.

Note : The file is not encrypted until you click OK. Also, additional users may not be added until the file has been encrypted by the first user.
* Click OK to encrypt the file.
* Open the file properties again through the Advanced properties button and then select the Details button to add additional users. Once the Details dialog box is open, the add user option will be displayed.


Note : Additional information is available in the Encryption Details dialog box which may be useful for troubleshooting purposes.

How to add users?

* Click the Add button

# A new dialog box will be presented showing the existing users and certificates that are cached in the "Other People" certificate store of the local machine. It will also allow new users to be added from the Active Directory by clicking the Find User button.

Note : A user must have a valid EFS certificate in the Active Directory to be added.

# Click the Find User button to find new users


# The standard object picker dialog box will be displayed and a search will be conducted.

A dialog box will display users that hold valid EFS certificates in the Active Directory based on your search criteria. If no valid certificate is found for the given user, the dialog box will be displayed saying "No appropriate Certificates correspond to the selected user"
If valid certificates exist in the userCertificate attribute of the user object in the directory, they will be displayed in the certificate selection dialog box.

Note : Windows XP now performs revocation checking on all certificates for other users when they’re added to an encrypted file. For performance reasons, users that hold a private key are not checked for revocation. However, certificates that do not contain a CDP (Certificate Revocation List Distribution Point) extension (such as those from some 3rd party CAs) will not be validated for revocation status. If the revocation status check on a certificate fails, the messages stating "An internal certificate chaining error has occured" -OR- "The signature of the certificate cannot be verified." will be shown.

If the revocation status and chain building completed successfully, the user will be added to the dialog box and the file will be updated accordingly.
# Click OK to register the change and continue.

Note : Any user that can decrypt a file can also remove other users—if the user doing the decrypting also has write permission.

Note : EFS has a limit of 256K in the file header for the EFS metadata. This limits the number of individual entries for file sharing that may be added. On average, a maximum of 800 individual users may be added to an encrypted file.

How to view the certificate for information?

You can select a user certificate, and view the certificate for information to make your administrative decision. To view a certificate, just follow the instructions:

* Highlight the certificate in the dialog box and click the View Certificate button.
* Click OK to close this dialog box when finished. You will be returned to the previous dialog box within which you can choose the appropriate user to be added to the encrypted file.
* Highlight the selected user certificate that you want to use and click OK.


Noe that encyption is so easy, Always encrypt your private and crucial data.... All the best...!


Source : techarena

10 points for choosing a right Processor

10 points for choosing a right Processor

Which processor is actually the fastest and how important are Hertz when you select new computer? I will clarify concepts and answer some of the most common questions about processors.


1. What is a processor?

Processor, often called the CPU (Central Processing Unit), is the brain of the computer where it accounts for most of the calculations made. There are processors in many types of gadgets, everything from microwave ovens to cars, here we focus however on the ones we have in our computers.
Modern processors can perform billions of calculations every second and they are made up of millions of small transistors mounted on a surface in a few square centimeters.


2. What is the difference between a CPU and a GPU?

CPU is not the only circuit in a computer that handles calculations, the graphics card in the computer is also usually a self-processor that only handles graphics calculations, this is sometimes called the GPU (Graphics Processing Unit).
Even the sound card may have an advanced dedicated processor.


3. What should I choose - AMD or Intel?

Since immemorial time we have AMD and Intel's been on the performance throne and there has always been arguments for both sides. What is the fastest, most power-efficient and most affordable? In the current situation Intel leads in terms of pure performance, while AMD instead focusing on being the affordable option for the budget with a little narrower. And so it has, with few interruptions, been quite a while. Important to know is that when you select the processor, select the platform, thus moderate style and in some cases a common style, so it will be easy to switch to another processor if you would change your mind.


4. How much power, the processor?

This has been the development properly forward the last two to three years and even if you select a fast dual core processor it need not absorb very much power. In this context used TDP (Thermal Design Power) as a unit, in practice the maximum effect that the cooling device must support to the CPU so that it does not overheat. The latest and fastest Core 2 Quad models from Intel is about 65-95 watts TDP, while a simpler dual core processor in a new laptop has TDP-values of around 25-35 watts.

Ultra Low Voltage flavors draws no more than 5-6 watts TDP and the latest Atom processor from Intel, a model that will appear in the mini-computers in the year, draws as little as 2.5 watts. Now that defines Intel and AMD TDP-value in different ways so the value, unfortunately, is not comparable across different platforms.


5. How many cores do I need?

The difference between a single core and a dual core processor is quite large but it is not as obvious to go up to Quad Core. If you're running heavy applications for audio or video editing, the four cores will be preferred (if your program supports this) but if you're looking for the best gaming performance, it is usually better to put money on a fast dual core processor and a fast graphics card. Few games can use more than two cores in the current situation and usually the graphics card is the weak link in terms of performance.


6. How many gigahertz do I need?

A few years ago you could compare hertz rates between different processors and thus get a decent idea of what was the fastest but it is as simple as it no longer. AMD and Intel use different processor architectures and the factors that bus, cache and number of grains to make it properly when you choose. Here it is more important than ever to read the tests and that you select a new and fresh processor so you do not stand with an old platform that you can not upgrade.


7. How much the cache?

The cache is built into the processor itself, which means that the data does not need to detour through working memory (RAM) before being processed. This means that when the cache is used calculations are much faster than otherwise. The more cache you have in the processor the faster the work is, but it is also an expensive component that draws up the overall price. This memory is also divided into different levels, L1, L2, etc. The lower the number the closer the actual processor (and faster).


8. Will I earn something on overclocking?

Overclocking can be a cheap way to get out a little more performance from your computer while you are charged to the processor more than its actual performance. Make sure you have a big cooler and check that your CPU is overclocking friendly (read in properly before). The rule on overclocking is that drawing up the speed of the system bus, thus increasing the CPU clock frequency, but at the same time, insert the motherboard to the test. Many new motherboards have overclocking features built-in smartly that you can control directly from Windows software.


9. Can I change the processor itself?

Before you buy a new processor to your computer, it is important that you have stone eye on the new processor fits in your motherboard. Not only physically but also to the motherboard software (bios) to identify the processor. The actual change is quite simple but you have my thumb in the hand it may be worthwhile to ask someone with experience for help. It can be an expensive business if you slip with the screwdriver when you mount the cooler.

And you are thinking of changing the processor in your laptop then usually just forget. If you are lucky, processor is not soldered but only to disassemble the chassis can be a nightmare and it's not safe to bios support your new CPU and cooler whether it can handle the heat development.


10. How important are the bits?

The major advantage of 64-bit processor and 64-bit operating system is that it can use significantly more working memory, is still software support, however, very limited. If you do not need to work with a workstation that will render 3D animations or similar applications, we recommend 32 bits. To take advantage of a 64-bit processor, software must have support for it.


Source : techarena


What is Conficker ?

What is Conficker ?


Conficker

Conficker, also known as "Downup", "Downadup" and "Kido", is a computer worm that surfaced in October 2008 and targets the Microsoft Windows operating system. The worm exploits a previously patched vulnerability in the Windows Server service used by Windows 2000, Windows XP, Windows Vista, Windows Server 2003, Windows Server 2008, Windows 7 Beta, and Windows Server 2008 R2 Beta. The worm has been unusually difficult for network operators and law enforcement to counter because of its combined use of advanced malware techniques.

Symptoms

* Account lockout policies being reset automatically.
* Certain Microsoft Windows services such as Automatic Updates, Background Intelligent Transfer Service (BITS), Windows Defender and Error Reporting Services disabled.
* Domain controllers responding slowly to client requests.
* Congestion on local area networks.
* Web sites related to antivirus software becoming inaccessible.

5 ways to avoid Conficker

Know this, that Conficker invading computers "vulnerable", ie those who do not have a system to date.

1: Do a Windows Update

First rule, which may seem obvious but is not given the number of infected machines: run an updated Windows Update! Note that on infected machines, ensures Conficker disable Windows Update and maintain disabled.

If you experience problems with Windows Update on your computer, directly download the patch that fixes the flaw exploited by Conficker following the appropriate link:

- For Windows XP
- For Windows Vista

2: Make sure the patch is installed

To verify that the patch is installed you can either use a program like Belarc Advisor or Microsoft Baseline Security Advisor, or simply make the next movement, go to Control Panel, the management module Add/Remove Programs (or simply "uninstall a program" in Vista), then check Show updates (or on Vista click "show all updates installed") and verify that the hotfix KB958644 is installed (in the Windows updates, while bottom of the list).

Quote:
Note to Vista users: If you installed the beta or RC version of Vista SP2 (Update KB955430), your computer is protected while the KB958644 patch does not appear.
3: Make sure there are no traces of Conficker on the system

Check Conficker that is not already more or less on your system. For this, the simplest is to use the detection/removal of malicious code from Microsoft.

Click on this link, then click Download, click Run, Run again, then Next, then complete analysis and then click Next. At the end of the analysis, click on View the detailed results of research to verify everything is OK and that Conficker was not detected.

4: Verify that there are no traces of Conficker on your network

Conficker can also spread by infecting files shared on the network. It is therefore essential, if you have multiple machines on the network or a NAS (hard drive connected to the network), to scan these areas potentially infected. Use your antivirus whether it is the latest version (2009 edition). Otherwise, use a scan line by calling for a personalized analysis and selecting the network drives. You can use Panda TotalScan.

5: Disable Autorun for removable devices

Conficker spreads, like many new malware, infecting the USB key. If you have an antivirus recent (2009 edition) it is very likely to include the management of devices and automatically scans the keys when they were introduced into the system. If you have any doubts on the subject, you can take safety measures preventing the automatic execution of programs with the introduction of a key (ie, deactivate AUTORUN.INF). To do this:

- Launch REGEDIT
- Deploy the key: "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\IniFileMapping\Autorun.inf"
- Double-click the value "(default)" and enter the data: @SYS:DoesNotExist

5 mistakes that make Conficker exists

Altogether, five principles for not being infected by malware as Conficker, five errors in behavior that have allowed Conficker to exist and spread.

1 - Do not enable automatic updates

Some so-called "experts" advise users not to activate the Automatic Windows Update on the pretext that you may encounter conflicts or be terminated if you use a pirated copy of XP and Vista. The truth is that not to activate the automatic mode of Windows Vista is the assurance of being infected very soon! Almost all exploits are created when Microsoft releases an update (after analysis of the patch).

Windows Update is not likely to crash your PC, since driver updates are not sent into the automatic mode. At worst, if there was an incident, you could always make a system restore or uninstall the patch disabling. As to piracy, Microsoft does not persecute users (and dealers) and do not use Windows Update as a cookie (that would be unnecessary, millions of PCs around the world use a pirated XP). To activate the automatic mode, launch the Security Center, click Automatic Updates and select Automatic.

2 - To be trapped like a blue by Rogues

Guess what? Since the threat Conficker there has come on the market a number of implausible "Removers", "SuperMegaAntivirus", "HyperAntispyware" and other programs that claim to security solutions and in fact are the Trojans! We call these programs "Rogues". They are very popular. Conclusion: Use of tools known and reputable companies, beware of all the antivirus that you offer "sites under" or "pop-up".

3 - Believing that there are non-infected keygens

Spread the word, piracy is the primary source of infection of the PC. Multiple Keygen Cracks and other available on the "news" and other P2P networks are infected. A recent test conducted has even shown a file of old crack downloaded a week on the "news" could be recognized by any antivirus or even updated VirusTotal and yet be terribly dangerous for Windows XP (Vista was able to resist infection even though the virus did nothing). However if the antiviral scans did nothing, the protections "real time" of most antivirus alerts posted in performance of the crack.

4 - Believing antivirus scans are useless

Some believe that the protections "real time" antivirus enough, and it is unnecessary to run scans. Bad idea. Typically, in the case of Conficker a virus from another computer from home can infect the network shared folders or network drives. Hence the importance of launching frequently not only complete scans of your hard disks, but also the shared folders of other machines or NAS.

5 - To believe that passwords are useless

Conficker spreads more easily than the profile on which it runs has no passwords. The software even has a mechanism that attempts to force the network passwords by trying passwords most common in the world and other techniques. Hence the importance of always using a profile is protected by a strong password consisting of at least 7 characters, 1 digit, 1 upper case and a sign (*, +, -, @, etc).


Source : techarena


Overclocking tutorial for newbies/beginners

Overclocking tutorial for newbies/beginners

Overclocking is about getting your computer to run faster than it actually is intended. To read further, and try some of the things I suggest is at your own risk.

If you are computer freak like myself, and not afraid to risk burning the processor, just read on. But if you are a little sore to your computer, you should probably stop here.

In any case, overclocking is to take small steps and make sure that your computer's cabinet is well chilled. If there is no proper cooling on your processor / graphics card then you are out of it.

This article is intended for beginners who want (and can afford to take risks) to address this. To go further in depth, I can recommend you to visit some expert and dedicated overclocking sites where you can find many guides to come forward.

* What is overclocking?

Overclocking is really rather simple. It's about getting your computer to run at a higher clock frequency than is intended. The benefit of overclocking is that you can buy a processor that runs at a given speed, and then put the clock rate up so it runs as fast as a much more expensive processor. The same can be done with similar way for RAM and graphics card.


* How do I get started?

Overclocking is a little dangerous, but it is not something that you threaten to break arms and legs of. To get started you should take a backup of your documents and important data. But if you are ready to bear up all things, there should not be major problems.

One of the things that will be good to have on hand is a diagnostic program that can monitor your processor temperature. I can recommend the Asus Probe, which can be downloaded for free at asus.com. It is designed for motherboards from Asus. If your motherboard is of a different manufacturer, the manufacturer has probably developed a similar piece of software that you can find on their website.


* What type of overclocking?

There are two different ways you can overclock your processor. One is called FSB-overclocking, and the other called Multiplier-overclocking. Ideally the FSB-overclocking is the easiest and most effective way to overclock, and therefore we will deal more with it.

Your processor works with two speeds. One speed is the internal, which is also the boast with you to your friends. My computer was running, for example, with 1333 MHz internally factory made. Now run it with 1450 Mhz because I have overclocked it

The second speed is the external, which the processor communicates with the rest of the system. If your computer was purchased within the last few years, the external velocity probably either 100 or 133 megahertz (MHz). Processor contact with the outside world otherwise known as the Front Side Bus (FSB) and the external velocity is just as FSB work with.


* Procedure for overclocking

If you have a backup, there is nothing wrong to go. Restart your computer and go into your bios setup.

Depending on your motherboard bios system will differ slightly from the menu items and descriptions, but I will try to describe it as well as I can.

Inside the bios, there will be a menu item called something like 'Advanced setup'. Under 'Bus Frequency" or "FSB Frequency" there should be something like 100 or 133. It allows you to change. It may be that you first have to change a default setting to manual setting.

Try to set your FSB frequency up to 5 megahertz to 138 MHz (if it was at 133 Mhz). Save your changes and your computer will now run with a relatively higher clock frequency. The internal speed of the processor is directly connected to the external velocity. The relationship between the two speeds are determined by the so-called 'multiplier', which I will come back to.. later.

If it runs stable you can try the same maneuver again and put the FSB further with 5 Mhz. You can do this until you observe that the system begins to make mistakes, and becomes unstable. When this happens, go back into bios and set the FSB down to 3-4 MHz. So would like to run the system stable.


* Where is FSB-overclocking?

FSB-overclocking works on your entire system at once, as you adjust to the whole motherboard internal communication speed. Therefore, both your processor, RAM, graphics card, etc. work faster when your FSB is overclocked. It also means that it is not necessarily your processor becoming breathless first. It could be your RAM or your PCI ports only get off. If so, you can successfully invest in additional cooling of these parts.


* What is Multiplier?

Multiplier is the factor that determines the processor's internal speed relative to FSB speed. My own computer has a FSB speed of 133 Mhz, and process variety is an AMD Athlon Thunderbird 1333Mhz. So Multipliers 10 because 133x10 = 1333 (not quite mathematically correct, but it goes )

If you raise your multiplier change only internal processor speed as the FSB speed will not change. So you will not achieve the same results with this type of overclocking. But if you already have overclocked your FSB and your RAM will not take more, the next step would be overclocking the multiplier.

However, it is not all processors that support this type of overclocking. AMD's processors will suffer a small action first, and Pentium 4 does not permit.


* What can I overclock otherwise?

One obvious thing to overclock is your graphics card. In demanding game you can revitalize your graphics card with a time overclocking. I can recommend the Power Strip, which provides an easy approach to this. The program can be downloaded here: http://www.entechtaiwan.com/ps.htm


* When I overclock, my computer will not start!

Then you probably been a little too aggressive with your overclocking. You can save the situation by going into bios and choose to load "Setup defaults". This will lower the FSB to normal and you should be able to boot (unless you burn something)


Source : techarena

How to maintain a database using Excel 2007

How to maintain a database using Excel 2007

Excel allows you to manage lists of all sorts, to retrieve data and to extract statistics. All without programming and in a few clicks.


You have to manage a file of members of an association, a collection of stamps, DVDs or good bottles? For this you have two options. Either you install a software of database management (DBMS) such as Access. But beware: such a program is not cheap (more than Rs. 13000 for Access 2007), or easy to use. The alternative is to use an Excel spreadsheet as widespread.

The latter, in fact, has many functions that allow you to enter or modify data in a collection, to extract information using a variety of criteria, to obtain data on all or part of the basis . Thus, on the basis of films such as the one we have chosen to illustrate this issue, you will see that in a few clicks, you will easily find things in less than 90 min, while this very intuitively and without learning programming language.

But what should you do to convert an Excel spreadsheet into a database? The answer is simple: nothing! Indeed, any list of data is automatically considered as a basis provided that a few simple rules of common sense that we detail in the following pages.

Leaving on good... bases

After reviewing the techniques to capture, edit and monitor data, we will see how to create simple queries, then using the complex functions of the spreadsheet. We detail the PivotTables, this magical summarizing statistical calculations the more complex a few mouse movements. Finally, we will finish this guide by sharing a database on a remote computer. To illustrate these pages, we will use Excel 2007, which brings several new features compared to the previous version. To track and rebuild our manipulation, no need to be an expert in the use of spreadsheet Microsoft at most should know the basics.

Limitations of a database using Excel 2007
The limits of a database with Excel

Excel is not a "real" database manager. While it is ideal for medium-size collections, there are some gaps that prohibit the management of large databases professional

- Number of records limited.

Although it is theoretically possible to enter data in all rows of a spreadsheet (over a million with Excel 2007!), It would be unwise to exceed a few tens of thousands of sheets (one sheet corresponds to a line). Indeed, Excel is working memory, unlike the real DBMS. The smallest crash or any power outage, all your changes are lost.

- Control input rudimentary.

Excel allows you to check the data entered by users. But it continues to be fairly brief. DBMS goes much further.

- One table.

Excel is not done to manage the foundation made up of several tables (eg Customers, Invoices, Stock ...). In fact, you might be achieved in part with cumbersome and complex, but your database would become too heavy.

- No referential integrity.

A DBMS provides referential integrity if it prohibits the removal of a record which still has links with records in other tables. For example: you can not delete a customer if there are still bills to his name. Deleting a file in Excel, not of consistency checks.

Step 1: Enter and verify data

1 - Make sure your list is an Excel

Every table in Excel, is automatically considered as a database if it meets a few simple rules and logic (it is probably already the case in your list):

A header row

The first line of your database (not necessarily line 1 of your Excel sheet) should contain the names of fields, all different. There is a field-by-column and one column per field. A field name must not contain space. We advise you to color the header line to make it more visible.

Only one type of data field

In a field (column), do not type the same data type: text, numbers or dates.

One line per card and a sheet-by-line

One form is the name under which we will designate part of your base (a member of the club, a movie ...)

No row or column blank in the base.

Consistent data

It is simple common sense: Always type in the same way the same data. Thus, Bombay and Mumbai will be considered as two different cities. Finally, when you enter titles (movies, books ...), always put this to the end. The sorting will be facilitated.


2 - Adjust the display

The first step on a large is to "freeze" the first line on the screen. In this way, the field names remain displayed when the leaf scroll. To do this, place the pointer on the first line under the header row in the left column. Activate the View menu. Click the Freeze Panes button, then on the menu with the same name. Take this opportunity to give each column width just need to ensure that all data are visible. To do this, place the insertion point between the letter head of the column and placed on the right. When the pointer becomes a black cross, double click. Repeat the same for the other columns of the base.

3 - Add and edit records

To create new files or modify existing files, you can take the course as you would any table. But it is more pleasant to do so in a form. Paradoxically, the order form, which appeared on the menus of previous versions of Excel, was hidden in the maze of Excel 2007! To make it available, click the small arrow to the right of the Quick Access Toolbar (top left) and select other commands. Pull down the list to the item form, click Add>> and then OK.

4 - Display the form

Place the pointer in any cell of the database and click the form that you just added to the Quick Access Toolbar. The form is displayed. You will not see a sheet at a time, but all fields are visible. To scroll through the database, use the scroll bar or the Back and Forward buttons. You can change values in any field. To validate this modification, press enter, or use one of the Previous or Next buttons.

5 - Add entry controls

In a basic entry, errors are a problem because they make it impossible or inconsistent calculations, selection and sorting. Excel allows you to control the data entered. We want, for example, that in the Price field (movies), can be entered as values between 2 and 30. Click on the header field of Price to select the entire column.

Activate the Data menu and click Data Validation, and then click the Options tab. In the Allow list, select Decimal. In the Data list, select Between ... Finally, type 2 in the Minimum field and 30 in the field possible. Enable the Error Alert tab. In the Title field, type error rate, then in the Error Message field, type the prices must be between 2 and 30. Click OK. Now, typing prohibits a prize will result in displaying an error message. You can, in this way, attribute checks all your fields, including those to contain numbers (prices, dates ...).

Attention, control input only applies to data that you enter: if off-limits numbers (eg prices above 30) are already in the database when you move the control, they will not change.

6 - Impose typing in a list

In the Type field (film), do not enter anything because it would be impossible to find a genre in the base. So if you are looking for films marked "Drama", you will not find those for which you have entered "Dramatic." Here is how to impose on the user input "closed." Create a new worksheet in your workbook by clicking on the button to the right of the tabs at the bottom left. In this new sheet, enter in a column contents allowed one per cell, leaving no empty cell. Check this list and, in the Name box in the upper left, type TheGenres and press OK (you can choose another name, but avoid using the names of the fields in your database).

Return to the worksheet titles, select the entire column D (Styles), open the Data Validation window (see above). In the field Allow, select List. Click in the Source field, press F3 and select TheGenres in the field list. Valid OK twice. Now, when you click in a cell type of the field, a list appears on the right and you can select an item.

7 - Create custom views

If the database must be accessed or modified by several people, all are not necessarily the same data. Thus, the film maker does not wish to display only the title, year, director and distribution, while the accounting wants to see the title, the number in stock (the field) and price. Finally, the seller wants the whole database to be visible (as is the case now). Activate the Display field, click Custom Views and then click Add. Enter Seller and click OK.

To create the view by accounting, hide columns Year, Genre, Director, Duration and Distribution (to hide a column, right-click on the letter to his head and choose Hide). Click Custom Views and then click Add. Enter Accounts and confirm with OK. Create the view of Film Maker on the same principle. Now, to activate a view, click Custom Views, and double-click the desired. Of course you can modify the database when a view is activated.

8 - Make the numbers

A significant novelty of Excel 2007 is its function as conditional formatting, more powerful and easier to use than previous versions. Here's how to bring out in the Price column, the most expensive films. Select column (Price), select the Home menu and click Conditional Formatting, then Bars data. Choose a color and click OK. Excel inserts in each cell colored bar width proportional to its value. You can also opt for a gradient of colors (red for the more expensive green for cheaper).

9 - Sort the contents of the database

Sorting is an essential function for any list of data: it allows, among other things, identify duplicates and to detect input errors. To make a simple sort, for example by years of declining output of films, select any cell in column C, select the Data menu and click on Z.. A for a descending sort (alphabetical, numerical or chronological by data type). Button A.. Z give him an ascending sort. Note: Do not select a field especially of several cells before sorting, because in this case, only the scope will be sorted ... and not other cells. Your base is totally mixed!

10 - Add criteria

By default, Excel does one sort key, which is often inadequate. Thus, in the previous example, if you want all films of the same year are ordered alphabetically by title, click Sort. The first sorting criterion (down by year) is already in place. Click Add and edit a new list until then by securities from A to Z. Then press OK.

In Excel 2007, finally sort accented characters in the "right" place. Thus, the word "variety" will be classified at the sorting, between "center" and "this". With older versions of Excel, the accented characters whose ASCII code is greater than all other letters of the alphabet, were relegated at the end.

11 - Choose a sort order arbitrary

If you sort your database by genre (Comedy, Drama ...), Excel will sort those categories alphabetically (or reverse). Thus, action will be placed before Comedy. You can impose an arbitrary sort order by creating a custom list, for example to place at the top of all categories of films recommended for such young Comedy, Action / Adventure, Musical ...

To do this in a new sheet (or the step 6), enter all kinds of films, in the order you want to impose the sort. Select the list and click the Office button in the upper left and choose Excel Options. In the Standard tab, click Edit custom lists, and then in the new window, click Import. Genres appear. Click OK twice. Finally, repeat the above steps by selecting Sort by Gender, Values, Custom list, select your new list and click OK twice.

12 - Protect data

It is possible to inadvertently overwrite important data in a column by typing a different content to the site. To avoid this inconvenience, you can protect the contents of the base. To do this, select all the cells you do not want the change (note: with previous versions of Excel, it should do the opposite!). Activate the Home menu, click Format and choose Lock the cell.

Once you have checked out all the fields, click the Format button and select Protect Sheet. Check the actions that you allow on the sheet locked (you can, for example, prohibit the insertion of rows or columns). Optionally, type a password and confirm by OK. If necessary, confirm your password. Henceforth, any attempt to write to a protected cell will result in an error message.

Step 2: Find information

1 - Use the Find / Replace

Is the basis of research. Looking, for example, films whose name contains diamond. Select column A (Titles). Activate the Home menu and click on Browse and select, then click Search. Diamond Type and click Next. The first title containing that word is selected. To scan all the others, click Next. The search is not case-sensitive: if you are looking for Diamond, you will also find DIAMOND. In contrast, the accented letters are considered (looking forest, you will not find forest).

2 - Use the form

The form you have activated and used in the previous chapter is not to add or modify files: it allows to find. Consider the following example: looking for movies for more than two hours (120 minutes) and produced after 1998. Click the Form button in the Quick Access Toolbar. When the form is displayed, click Criteria. In the Duration field, type> 120 and, in the Year field, type> 1998. Press Enter. Excel displays (if any) the first movie that meets your criteria. To "scan" the answers, use the Back and Forward buttons, but not the scroll bar, because in this case all records from the basis that scrolled.

3 - Use the filters

Queries made with a form are fairly rudimentary. Basically, they are effective only with numerical comparisons. No way, for example, to search for films with a specific actor, especially if it is in the middle of the distribution list. To do this, you use the automatic filters. Activate the Data menu and click the Filter button. A small black triangle appears in each header field (another click the same button makes them all disappear). For the example treated in the preceding paragraph (movies over 120 minutes produced after 1998), click on the triangle located in the Duration field and select Digital Filters, Above. In the window that appears, enter 120 on the right of more than ... "and click OK.

You notice that the small triangle in the button Time has changed: it now represents a small filter. This lets you know that the information in this column are filtered. In other words, that the base is no longer displayed in full. For the same reason, the line numbers to the left of the screen is blue. Repeat this for only those films whose Year field contains a value greater than 1998. Each time you put a filter on a field, this filter is in addition to those already in place. These filters play a cumulative role, allowing you to gradually refine your search by adding criteria to gradually reduce the number of responses.

4 - Combine the criteria

How to find films with Aishwarya Rai. Click on the triangle located in the Distribution and choose Text Filters (Excel has recognized that this field contains the text and not numbers) and choose Contains. Enter Rai and confirm with OK. You can, in the entry criteria, add other words, for example Rai AND Bachchan or Rai OR Bachchan. In the fields of criteria, such as forms, capital letters are ignored, but not accented.

5 - Find Duplicates

Can you say that you never have before in double (even triple!) Certain records of your database? Probably not. To find out, use the Search for duplicates, another new feature of Excel 2007. Select any cell in your database, select the Data menu and click on Search for duplicates. Then select the fields on which your research. Warning: if you select all, Excel does indicate, as duplicates, the files are strictly identical to the last comma. Better tick only significant fields (eg Title, Director). Finally, click OK. The double sheets are automatically erased.

6 - Use a simple field criteria

For more sophisticated needs (eg looking for three players), we advise you to use criteria fields (we use in the next chapter, devoted to calculations). For example, a customer looking for films which have played one or several of his favorite actors: Akshay kumar, Ajay Devgan and Kajol. Open a sheet in your workbook (or use one you have added to enter the lists ). In a blank, key distribution (it should be the exact name of the field on which your research). Below, type successively *Akshay*, *Ajay* and *Kajol* in three cells. Note that each name is surrounded by stars (we will return). Give these four cells MyCriteria name (no spaces). Return to the worksheet titles, select any cell in the distribution field and click the Advanced button (right of the Sort button). Do not change the contents of the field Beaches, click in the area of criteria and press F3. In the list of field names, MyCriteria then click OK twice.

With our example - if you have not changed - you should find 31 films (the number of results is shown below). The area criterion works as follows: all elements placed in a column are connected by an OR. Excel research therefore films played by Akshay OR Kajol OR Ajay. (Here, OR is to take effect from and/or). As the stars they represent, in the search criteria, any number of characters. Thus, *Akshay* means any number of letters, then Akshay, then any number of letters. Logically: the word Akshay can be anywhere in the list of players. If you enter Akshay instead of *Akshay*, Excel will seek the cards whose field distribution contains only the word Akshay ... and do not find any!

7 - Add a condition

Complicated matters somewhat. The lover of films mentioned in the preceding paragraph is putting less than Rs. 780 per film. We must therefore add a second criteria. Go back to your field of criteria and complete it as discussed previously. Set this field of 2 columns x 4 rows NotTooExpensive name. Back titles on the sheet and repeat the manipulations of the above step in choosing this time the criteria NotTooExpensive. You should find more than 9 movies. The explanation is simple: all elements of the same line in an area of criteria are linked by AND. Excel seeks films that meet the following criteria (containing Actor Akshay AND Price<780)>

Attention to a classic mistake: if you write<780>

8 - Extract a part of the basis

In all the examples you have dealt so far, you get a partial view of the base. If you want to get these results, for example to copy them to another workbook, you must do otherwise. Define your criteria field (see step 6). In the window of defining criteria, select Copy to another location. In the Copy To field, enter the destination address (specifically, the address of the cell placed in the top left of the field to copy the results), then click OK. Note that the scope of results obtained is independent of the initial base. If it is changed, the field results will not be updated.
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Step 3: Make calculations on the basis

1 - Use the aggregation functions

The calculation as simple as could be done with a collection of data is an aggregation by criteria. You want to, for example, determining the number of films by genre (ie a combination of all the contents of the column Nb). By number of films, we mean the total number of discs and not many different titles. For this you must first sort your base on this criterion. Select a cell in column D, activate the Data menu and click A.. Z. Click Sub-Total.

In the window that appears, scroll down the list each change and choose Genre.... In the Add subtotal to, check Nb (number of films) and uncheck all other boxes. Validate by OK. Look at the left of your screen you can see two vertical lines and, above, three small buttons 1, 2 and 3. This means that Excel has activated the Outline view. Click 2: the spreadsheet hides all the files just to show the totals, the result you want. Now click on 1: only the grand total is displayed. Finally, if you click on 3, all the cards are visible: the display of your database.

2 - Create a calculated field

You now want to obtain the monetary value of your stock, thus increasing the total for each title, its price by the number (Nb) discs. However, there is no Value field in the list. It would indeed be to redundancy in a field whose content is derived from other fields. You will use the column I, hitherto idle (remember: no empty column in a database). In I1, key value, the name of the calculated field. In I2, enter the formula = B2 * E2. Place the cell pointer in the bottom right of I2 (the pointer turns into a black cross) and double-click: the formula is repeated on all the cells in column I. All you have to repeat step 01 but by choosing this time a total of the Value field (which was automatically added to your base). If necessary, hide columns E, F and G for easier reading of results.

3 - Add an arbitrary criterion

Sometimes it is necessary to perform tabulations on a criterion that can not be inferred directly. For example, you want to count the number of securities by the length of film. Unable to use the Subtotal on the duration field because the latter, expressed in minutes, has a different value for almost all films. You would get a total too fragmented and unmanageable. Create a calculated field, you call CatDuration (Class Period), and where you will be a code, eg 1 for films of less than one hour, 2 for films between 61 and 90 minutes, 3 for films between 91 and 120 minutes and 4 for longer films. These thresholds are arbitrary, you can edit at leisure. To obtain this code directly in terms of duration, place the formula = IF (G2 <60,>

4 - Make statistics on your database

The total raised in the previous steps apply to all of the base. If you want to perform calculations on a portion of your list, you must use the statistical functions of a database. These functions, whose name begins with NB (NBSUM, NBAVERAGE ...) are different from their conventional counterparts (SUM, AVERAGE ...) with a capital: they apply only to cells filtered through a zone criteria like the one we saw earlier (see step 2, paragraph "Use a simple field criteria).

For example, you want to know the average price of comedies in your database. Start by giving a name to your database. It is not essential, but it makes the formulas easier to read. In the main sheet (Parts), click in any cell of the base, press Ctrl + * (Ctrl-star) to select all and give him the name MyFilms. Then insert a sheet in your workbook (or use that you added to enter the lists of entry). Type in a cell Genre Comedy and just below. Give these two cells AveragePriceByGenre name (no spaces). Eventually, enter below a label explains, for example, average price for this. Finally, in the cell intended to receive the results, it will enter the formula = BDAVERAGE (MyFilms; "Price"; AveragePriceByGenre). The first argument (MyFilms ) is the extent of the field on which the calculation. The second ( "Price", do not forget the quotation marks) is the field to calculate. The last argument (AveragePriceByGenre) denotes the area of criteria.

Now, for the average of the genre films, type the word in place of Comedy: the result is immediately updated. If a price change in the base, the formula takes into account immediately. We advise you to check the entry in the cell where you type the names of its kind (for that, see the paragraph imposes typing in a list, in step 1). By using areas of complex criteria, such as we have seen above, you can perform any calculation. Excel offers many other functions of this type, for example BDMAX (maximum), BDMIN (minimum), BDNB (number of sheets), BDECARTYPE (standard deviation for statistical calculations).

5 - Create a PivotTable

With PivotTables (PT), a feature already present in previous versions of the spreadsheet, but greatly improved in Excel 2007, you have an extraordinarily effective tool to talk about your numbers. To create such a table, select the worksheet containing your database, select the Insert menu and click PivotTable. Do not change the fields in the dialog box and click OK. You get the blank form to create a PT. The upper zone contains all the field names of your database. We will make a number of films per year of output. Drag the button to the Year Labels lines.

Finally, drag the field to the Number Values. Your PT shows a total field of Nb (thus the total number of disks) for each year.

6 - Add a second dimension

You now want to obtain a state per year, but also by types of films. In the form of PT, to the right of the screen, drag the button to the Genre column labels. Your PT is immediately recalculated.

7 - Reorganize Table

On the same principle, you can add fields in the row labels or column labels or move from field to field to change the criteria for consolidation. On the screen below, we switched fields inserted in the preceding paragraph. You can place multiple fields in one area: you get the sort at several levels, for example years then, in each year by directors.

8 - Ask a filter

You will not want to see that films released after 1990? In the table of values to the left of the screen, click the small triangle to the left of line labels and applying filters to select labels, Greater than or equal to and confirm with OK. In choosing to apply filters values, you could, for example, only the years for which there are more than 60 films in your stock.

9 - Add graphics

With the new Excel 2007, you can make your data more explicit. Return to the main sheet (Parts), activate the Insert menu. Do not click PivotTable, but on the small triangle adjacent to this button, then choose PivotChart. Click OK and choose your data fields as with PT in the previous steps.

Step 4: Sharing a remote

1 - Prepare the base

Sharing a database between multiple remote users has many advantages. Indeed, only one person modifies this base by adding, changing or deleting a file, so that all other immediately have a list up to date. To build such a structure with Excel, you do not need other software. You simply have an Internet connection and a storage space, as proposed in almost all providers. Suppose, for example, that our selection of films is the content of a lending library. By putting the data online, it becomes possible for everyone, both the operator of the library, or a member, whether a particular movie is available.

However, these are not the same for different users. The operator, for example, wish to know the price of the DVD. The member, in contrast, will display the length of the film. Excel allows you to give everyone a display adapted to their needs while using common data. You just need to separate the binder into two parts. A data part, stored in an Excel workbook and put on an online site and a second workbook, linked to the first, but deals only with the 'view' of data.

In the second workbook, you can, for example, for sorting, extracting information, or draw a graph from the data. Each user therefore has a display of its own, customized to their needs and stored locally on the hard disk of a PC. This file must be able to automatically connect to the Internet to obtain the data. Conversely, the workbook data itself is present on your website.

2 - Create the new workbook

To provide such data Excel, just export only leaf binder Securities Films.xlsx in a new workbook. Make sure that the sheet is currently displayed in full, ie without filters, hidden columns or rows, custom displays, or other options ... Right-click the mouse on the Titles tab. Pull down the menu Move or Copy. Select the workbook: (New file), check Create a copy and confirm by OK. Excel creates a new folder named Parts.xlsx.

3 - Place on the Internet

You need a hosting site (and FTP). Most ISPs offer you a personal space than sufficient for this purpose. Alternatively, you can easily create (and free) such a space, eg, Free or on 0fees.net. In Excel and with the workbook Titles.xlsx open, click the Office button and pull down the menu Save As, Other formats. In the File Name box, enter the address of your FTP server in the form ftp://mylogin@serverftp.supplier.com (eg ftp://foo@ftppersonal.free.com). You are then prompted for the password. Check the box Save password and confirm by Sign. The contents of the FTP server is displayed in the window.

Warning: some hosts, the data will not be placed in the root folder, but in a subfolder called web or www. If your base does not appear, So to explore the contents of these files. In the Type box, select Web Page in single file and confirm with Save and then Yes. Excel may ask you to enter the username and password. In this case, make sure that the Anonymous option is not selected and press OK. If this is your first FTP connection, Excel will ask you also to unblock the firewall.

4 - Check which transfer has taken place

Make sure now that the file is available. Launch Internet Explorer and enter the address of your site followed by /titles.mht (eg http://foo.free.com/titles.mht): your browser should give you a list of films. You notice that the data are now in a MHT file extension. It is simply a special HTML file containing text and images from any workbook. In our example, there is no picture, but the principle remains valid.

5 - Create the display file

In Excel, close the workbook and open titles, if not, the workbook Films. Activate the Titles tab and select cell A1. Now, select the Data tab, then click From website. Enter, in the navigation bar, the address you type into your browser (http://foo.free.com/titles.mht). The list appears with yellow arrow next to certain items. Click the second from the top to select all the data. The arrow turns into a green check mark.

The attributes of the original cell, such as background color or the police, are not displayed by default. You can choose to maintain these attributes by clicking the Options button, the option Formatting complete HTML and then clicking OK. Validate by clicking on the Import button.

Excel will ask you to where it needs to insert the data from the Web. Simply click OK to replace the existing title. The data are then fully inserted. It only remains for you to use the sheet "normally", sorting, extraction, graphics or other options on this new piece performed exactly as we described in the previous pages.

6 - Choose the options for updating

By default Excel 2007 does not automatically update the database when a change takes place. Indeed, this update can be applied to a cell in which another person is working, causing some confusion. In addition, Excel strictly control the use of external data in order to prevent copies of unwanted information.

To avoid these messages systematically opening the workbook Films.xlsx, pull down menu, click the Options button and then open the Excel Center Management confidentiality. Click Management Center of confidentiality and Content externally. Check the "Enable all data connections and Enable automatic update for all the routes of this workbook. Validate OK twice. In the workbook titles, open the ribbon and then click Data Connections. Check Update data when opening the file. Confirm with OK. Save the workbook.
Now, when loading a file, based on the local PC will be automatically updated with the read data in the database remotely. If you have set up filters in your workbook, think of them again by clicking in the Data ribbon, on Reapply button.

7 - Update the data file

Files with extension mht are directly readable by Excel 2007. In these conditions, update the data file is simple. Quit and restart Excel to close all current connections, you avoid a few bugs related to the cache. Click the Office button. If the file titles.mht is present in the list of recent documents, simply click it to open. Otherwise, click Open, type the file name in the address of your FTP server (ftp://foo@ftppersonal.free.com/titles.mht) and click OK.

The file appears after a few seconds in Excel. It only remains for you to make corrections, add or delete rows... Save the document normally (by clicking on the disk in the upper left), click Yes. The file is saved directly to your FTP server. For the same reasons as above, close Excel before opening the file and display films.xlsx in the Titles tab changes.


Source : techarena

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