System software

System software

System software is a generic term referring to any computer software which manages and controls the hardware so that application software can perform a task. It is an essential part of the computer system. An operating system is an obvious example, while an OpenGL or database library are less obvious examples. System software contrasts with application software, which are programs that help the end-user to perform specific, productive tasks, such as word processing or image manipulation.

If system software is stored on non-volatile storage such as integrated circuits, it is usually termed firmware.

Systems software – a set of programs that organise, utilise and control hardware in a computer system

Refers to the operating system and all utility programs that manage computer resources at a low level. Software is generally divided into systems software and applications software. Applications software comprises programs designed for an end user, such as word processors, database systems, and spreadsheet programs. Systems software includes compilers, loaders, linkers, and debuggers.

System programming

Systems programming (or system programming) is the activity of programming system software. The primary distinguishing characteristic of systems programming when compared to application programming is that application programming aims to produce software which provides services to the user (e.g. word processor), whereas systems programming aims to produce software which provides services to the computer hardware (e.g. disk defragmenter). It also requires a greater degree of hardware awareness.

In system programming more specifically:

1. the programmer will make assumptions about the hardware and other properties of the system that the program runs on, and will often exploit those properties (for example by using an algorithm that is known to be efficient when used with specific hardware)

2. usually a low-level programming language or programming language dialect is used that:

a. can operate in resource-constrained environments

b. is very efficient and has little runtime overhead

c. has a small runtime library, or none at all

d. allows for direct and "raw" control over memory access and control flow

e. lets the programmer write parts of the program directly in assembly language

3. debugging can be difficult if it is not possible to run the program in a debugger due to resource constraints. Running the program in a simulated environment can be used to reduce this problem.

Systems programming is sufficiently different from application programming that programmers tend to specialize in one or the other.

In system programming, often limited programming facilities are available. The use of automatic garbage collection is not common and debugging is sometimes hard to do. The runtime library, if available at all, is usually far less powerful, and does less error checking. Because of those limitations, monitoring and logging are often used; operating systems may have extremely elaborate logging subsystems.

Implementing certain parts in operating system and networking requires systems programming (for example implementing Paging (Virtual Memory) or a device driver for an operating system).

Originally systems programmers invariably wrote in assembly language. Experiments with hardware support in high-level languages in the late 1960s led to such languages as BLISS and BCPL, but C, helped by the growth of UNIX, became ubiquitous in the 1980s. More recently Embedded C++ has seen some use, for instance in the I/O Kit drivers of Mac OS X.

Computer software

Computer software is a general term used to describe a collection of computer programs, procedures and documentation that perform some task on a computer system. ^[1] The term includes application software such as word processors which perform productive tasks for users, system software such as operating systems, which interface with hardware to provide the necessary services for application software, and middleware which controls and co-ordinates distributed systems.

The term "software" is sometimes used in a broader context to describe any electronic media content which embodies expressions of ideas such as film, tapes, records, etc.

Computer software is so called in contrast to computer hardware, which encompasses the physical interconnections and devices required to store and execute (or run) the software. In computers, software is loaded into RAM and executed in the central processing unit. At the lowest level, software consists of a machine language specific to an individual processor. A machine language consists of groups of binary values signifying processor instructions (object code), which change the state of the computer from its preceding state. Software is an ordered sequence of instructions for changing the state of the computer hardware in a particular sequence. It is usually written in high-level programming languages that are easier and more efficient for humans to use (closer to natural language) than machine language. High-level languages are compiled or interpreted into machine language object code. Software may also be written in an assembly language, essentially, a mnemonic representation of a machine language using a natural language alphabet. Assembly language must be assembled into object code via an assembler.

The term "software" was first used in this sense by John W. Tukey in 1958.^[3] In computer science and software engineering, computer software is all computer programs. The concept of reading different sequences of instructions into the memory of a device to control computations was invented by Charles Babbage as part of his difference engine. The theory that is the basis for most modern software was first proposed by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem.^[

Types

Practical computer systems divide software systems into three major classes: system software, programming software and application software, although the distinction is arbitrary, and often blurred.

Ø System software helps run the computer hardware and computer system. It includes operating systems, device drivers, diagnostic tools, servers, windowing systems, utilities and more. The purpose of systems software is to insulate the applications programmer as much as possible from the details of the particular computer complex being used, especially memory and other hardware features, and such accessory devices as communications, printers, readers, displays, keyboards, etc.

Ø Programming software usually provides tools to assist a programmer in writing computer programs and software using different programming languages in a more convenient way. The tools include text editors, compilers, interpreters, linkers, debuggers, and so on. An Integrated development environment (IDE) merges those tools into a software bundle, and a programmer may not need to type multiple commands for compiling, interpreter, debugging, tracing, and etc., because the IDE usually has an advanced graphical user interface, or GUI.

Ø Application software allows end users to accomplish one or more specific (non-computer related) tasks. Typical applications include industrial automation, business software, educational software, medical software, databases, and computer games. Businesses are probably the biggest users of application software, but almost every field of human activity now uses some form of application software. It is used to automate all sorts of functions.

Program and library

A program may not be sufficiently complete for execution by a computer. In particular, it may require additional software from a software library in order to be complete. Such a library may include software components used by stand-alone programs, but which cannot work on their own. Thus, programs may include standard routines that are common to many programs, extracted from these libraries. Libraries may also include 'stand-alone' programs which are activated by some computer event and/or perform some function (e.g., of computer 'housekeeping') but do not return data to their calling program. Programs may be called by one to many other programs; programs may call zero to many other programs.

Three layers

Users often see things differently than programmers. People who use modern general purpose computers (as opposed to embedded systems, analog computers, supercomputers, etc.) usually see three layers of software performing a variety of tasks: platform, application, and user software.

Platform software

Platform includes the firmware, device drivers, an operating system, and typically a graphical user interface which, in total, allow a user to interact with the computer and its peripherals (associated equipment). Platform software often comes bundled with the computer. On a PC you will usually have the ability to change the platform software.

Ø Application software

Ø Application software or Applications are what most people think of when they think of software. Typical examples include office suites and video games. Application software is often purchased separately from computer hardware. Sometimes applications are bundled with the computer, but that does not change the fact that they run as independent applications. Applications are almost always independent programs from the operating system, though they are often tailored for specific platforms. Most users think of compilers, databases, and other "system software" as applications.

Ø User-written software

Ø User software tailors systems to meet the users specific needs. User software include spreadsheet templates, word processor macros, scientific simulations, and scripts for graphics and animations. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is. Depending on how competently the user-written software has been integrated into purchased application packages, many users may not be aware of the distinction between the purchased packages, and what has been added by fellow co-workers.

operating system

From the 1950s, computers use Operating Systems. In very simple terms, the purpose of a computer operating system is twofold: it offers services to application programs (such as hiding the technical details of disk access to applications), and it coordinates system resources if more than one program is started simultaneously. Examples of such resources include working memory and peripherals. An operating system also resolves the chicken-and-egg problem that programs usually are loaded and started by other programs, e.g. as requested by the user, but those starter program have to be started as well. There used to be standalone programs e.g. to format disks, needing no operating system, loaded by a 'boot' procedure also used for operating systems. So an operating system is not fundamentally indispensable.

An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. At the foundation of all system software, an operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking and managing file systems. Most operating systems come with an application that provides a user interface for managing the operating system, such as a command line interpreter or graphical user interface. The operating system forms a platform for other system software and for application software. Linux and Mac OS (or any other BSD-derivative) are popular UNIX-like operating systems.

The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.

Operating systems can be classified as follows:

· multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.

· multiprocessing : Supports running a program on more than one CPU.

· multitasking : Allows more than one program to run concurrently.

· multithreading : Allows different parts of a single program to run concurrently.

· real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.

Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.

As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.

Graphical user interfaces

Today, most modern operating systems contain Graphical User Interfaces . A few older operating systems tightly integrated the GUI to the kernel—for example, in the original implementations of Microsoft Windows and Mac OS the Graphical subsystem was actually part of the operating system. More modern operating systems are modular, separating the graphics subsystem from the kernel (as is now done in Linux, and Mac OS X) so that the graphics subsystem is not part of the OS at all.

Many operating systems allow the user to install or create any user interface they desire. The X Window System in conjunction with GNOME or KDE is a commonly found setup on most Unix and Unix derivative (BSD, Linux, Minix) systems.

Graphical user interfaces evolve over time. For example, Windows has modified its user interface almost every time a new major version of Windows is released, and the Mac OS GUI changed dramatically with the introduction of Mac OS X in 2001.

Device drivers

A device driver is a specific type of computer software developed to allow interaction with hardware devices. Typically this constitutes an interface for communicating with the device, through the specific computer bus or communications subsystem that the hardware is connected to, providing commands to and/or receiving data from the device, and on the other end, the requisite interfaces to the operating system and software applications. It is a specialized hardware-dependent computer program which is also operating system specific that enables another program, typically an operating system or applications software package or computer program running under the operating system kernel, to interact transparently with a hardware device, and usually provides the requisite interrupt handling necessary for any necessary asynchronous time-dependent hardware interfacing needs.

The key design goal of device drivers is abstraction. Every model of hardware (even within the same class of device) is different. Newer models also are released by manufacturers that provide more reliable or better performance and these newer models are often controlled differently. Computers and their operating systems cannot be expected to know how to control every device, both now and in the future. To solve this problem, OSes essentially dictate how every type of device should be controlled. The function of the device driver is then to translate these OS mandated function calls into device specific calls. In theory a new device, which is controlled in a new manner, should function correctly if a suitable driver is available. This new driver will ensure that the device appears to operate as usual from the operating systems' point of view for any person.

Application software

Application software is a subclass of computer software that employs the capabilities of a computer directly and thoroughly to a task that the user wishes to perform. This should be contrasted with system software which is involved in integrating a computer's various capabilities, but typically does not directly apply them in the performance of tasks that benefit the user. In this context the term application refers to both the application software and its implementation.

A simple, if imperfect analogy in the world of hardware would be the relationship of an electric light bulb (an application) to an electric power generation plant (a system). The power plant merely generates electricity, not itself of any real use until harnessed to an application like the electric light that performs a service that benefits the user.

Typical examples of software applications are word processors, spreadsheets, and media players.

Multiple applications bundled together as a package are sometimes referred to as an application suite. Microsoft Office and OpenOffice.org, which bundle together a word processor, a spreadsheet, and several other discrete applications, are typical examples. The separate applications in a suite usually have a user interface that has some commonality making it easier for the user to learn and use each application. And often they may have some capability to interact with each other in ways beneficial to the user. For example, a spreadsheet might be able to be embedded in a word processor document even though it had been created in the separate spreadsheet application.

User-written software tailors systems to meet the user's specific needs. User-written software include spreadsheet templates, word processor macros, scientific simulations, graphics and animation scripts. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is.

In some types of embedded systems, the application software and the operating system software may be indistinguishable to the user, as in the case of software used to control a VCR, DVD player or Microwave Oven.

Application software vs. Operating system

The exact delineation between the operating system and application software is not precise, however, and is occasionally subject to controversy. For example, one of the key questions in the United States v. Microsoft antitrust trial was whether Microsoft's Internet Explorer web browser was part of its Windows operating system or a separable piece of application software. As another example, the GNU/Linux naming controversy is, in part, due to disagreement about the relationship between the Linux kernel and the Linux operating system.

Application software classification

There are many subtypes of application software:

Ø Enterprise software addresses the needs of organization processes and data flow, often in a large distributed ecosystem. (Examples include Financial, Customer Relationship Management, and Supply Chain Management). Note that Departmental Software is a sub-type of Enterprise Software with a focus on smaller organizations or groups within a large organization. (Examples include Travel Expense Management, and IT Helpdesk)

Ø Enterprise infrastructure software provides common capabilities needed to create Enterprise Software systems. (Examples include Databases, Email servers, and Network and Security Management)

Ø Information worker software addresses the needs of individuals to create and manage information, often for individual projects within a department, in contrast to enterprise management. Examples include time management, resource management, documentation tools, analytical, and collaborative. Word processors, spreadsheets, email and blog clients, personal information system, and individual media editors may aid in multiple information worker tasks.

Ø Content access software is software used primarily to access content without editing, but may include software that allows for content editing. Such software addresses the needs of individuals and groups to consume digital entertainment and published digital content. (Examples include Media Players, Web Browsers, Help browsers, and Games)

Ø Educational software is related to Media and Entertainment Software, but has distinct requirements for delivering evaluations (tests) and tracking progress through material. It is also related to collaboration software in that many Educational Software systems include collaborative capabilities.

Ø Simulation software are computer software for simulation of physical or abstract systems for either research, training or entertainment purposes.

Ø Media development software addresses the needs of individuals who generate print and electronic media for others to consume, most often in a commercial or educational setting. This includes Graphic Art software, Desktop Publishing software, Multimedia Development software, HTML editors, Digital Animation editors, Digital Audio and Video composition, and many others.

Ø Product engineering software is used in developing hardware and software products. This includes computer aided design (CAD), computer aided engineering (CAE), computer language editing and compiling tools, Integrated Development Environments, and Application Programmer Interfaces.

Utility

Utility software (also known as service program, service routine, tool, or utility routine) is a type of computer software. It is specifically designed to help manage and tune the computer hardware, operating system or application software, and perform a single task or a small range of tasks; as opposed to application software which tend to be software suites. Utility software has long been integrated into most major operating systems.

Ø Disk defragmenters. Examples include a Disk defragmenter which can detect computer files whose contents have been stored on the hard disk in disjointed fragments, and move the fragments together to increase efficiency; a Disk checker can scan the contents of a hard disk to find files or areas that are corrupted in some way, or were not correctly saved, and eliminate them for a more efficiently operating hard drive; a Disk cleaner can find files that unnecessary to computer operation, or take up considerable amounts of space. Disk cleaner helps the user to decide what to delete when his hard disk is full.

Ø System Profilers. A System profiler can provide detailed information about the software installed and hardware attached to the computer. Backup software can make a copy of all information stored on a computer, and restore either the entire system (e.g. in an event of disk failure) or selected files (e.g. in an event of accidental deletion). Disk compression software can transparently compress the contents of the hard disk, in order to fit more information to the drive.

Ø Virus scanners. Virus Scanners scan for computer viruses among files and folders.

Ø Binary/Hex/Text Editor utility directly modify the text or data of a file without the WYSIWYG view in editor suites. These files could be data or an actual program.

Ø Archive utilities output a stream or a single file when provided with a directory or a set of files. Archive utilities, unlike archive suites, usually do not include compression or encryption capabilities. Some archive utilities may even have a separate un-archive utility for the reverse operation.

Ø Compression utilities output a shorter stream or a smaller file when provided with a stream or file.

Ø Encryption utilities use a specific algorithm to produce an encrypted stream or encrypted file when provided with a key and a plaintext.

Ø Application launchers—see Comparison of applications launchers.

A program that performs a very specific task, usually related to managing system resources. Operating systems contain a number of utilities for managing disk drives, printers, and other devices.

Utilities differ from applications mostly in terms of size, complexity and function. For example, word processors, spreadsheet programs, and database applications are considered applications because they are large programs that perform a variety of functions not directly related to managing computer resources.

Utilities are sometimes installed as memory-resident programs. On DOS systems, such utilities are called TSRs.

Program

An organized list of instructions that, when executed, causes the computer to behave in a predetermined manner. Without programs, computers are useless.

A program is like a recipe. It contains a list of ingredients (called variables) and a list of directions (called statements) that tell the computer what to do with the variables. The variables can represent numeric data, text, or graphical images.

There are many programming languages -- C, C++, Pascal, BASIC, FORTRAN, COBOL, and LISP are just a few. These are all high-level languages. One can also write programs in low-level languages called assembly languages, although this is more difficult. Low-level languages are closer to the language used by a computer, while high-level languages are closer to human languages.

Eventually, every program must be translated into a machine language that the computer can understand. This translation is performed by compilers, interpreters, and assemblers.

When you buy software, you normally buy an executable version of a program. This means that the program is already in machine language -- it has already been compiled and assembled and is ready to execute.

A computer program is a collection of instructions that describes a task, or set of tasks, to be carried out by a computer.^{[citation needed]} More formally, computer programs can be described as an expression of a computational method written in a computer language.^[1]

Computer programs may be categorized along functional lines. These functional categories include application software, operating systems, video games, and compilers, among others. Computer programs embedded in hardware devices are called firmware.

The formal expression of computational methods in a human-readable computer language is often referred to as source code, while the machine-executable expressions of computational methods are commonly referred to as executables, object code, or simply as binaries — a reference to the binary file format commonly used to store the executable code.

Commercial computer programs aimed at end users are commonly referred to as application software by the computer industry, as these programs are focused on the functionality of what the computer is being used for (its application), as opposed to being focused on system-level functionality (for example, as the Windows operating system is). In practice, colloquially, both application software and system software may correctly be referred to as programs, as may the more esoteric firmware — software firmly built into an embedded system

Program execution

A computer program exists in a source code form, viewable as a programming language; as a tokenised form, ready to be interpreted; or in machine code form, ready to be executed. (An aside: source code form may also be interpreted.) Computer programs can be divided into two categories — system software and application software. System software is the operating system that couples the computer's hardware with the application software. Application software couples the system software with the user interface.

A computer program is loaded into memory (usually by the operating system) and then executed ("run"), instruction by instruction, until termination, either with success or through software or hardware error.

Before a computer can execute any sort of program (including the operating system, itself a program), the computer hardware must be initialized. This initialization is done in modern PCs by a piece of software stored on programmable memory chips installed by the manufacturer, called the BIOS. The BIOS will attempt to initialize the boot sequence, making the computer ready for higher-level program execution.

Programs vs. Data

The executable form of a program (that is, usually object code) is often treated as being different from the data the program operates on. In some cases this distinction is blurred with programs creating, or modifying, data, which is subsequently executed as part of the same program (this is a common occurrence for programs written in Lisp), see self-modifying code.