Software

Software is a set of programs, which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem.
There are two types of software

• System Software
• Application Software

System Software

The system software is collection of programs designed to operate, control, and extend the processing capabilities of the computer itself. System software are generally prepared by computer manufactures. These software products comprise of programs written in low-level languages which interact with the hardware at a very basic level. System software serves as the interface between hardware and the end users.
software designed to operate the computer hardware and to provide a platform for running application software
Some examples of system software are Operating System, Compilers, Interpreter, Assemblers etc.

Features of system software are as follows:

• Close to system
• Fast in speed
• Difficult to design
• Difficult to understand
• Less interactive
• Smaller in size
• Difficult to manipulate
• Generally written in low-level language

Application Software

Application software products are designed to satisfy a particular need of a particular environment. All software applications prepared in the computer lab can come under the category of Application software.
Application software may consist of a single program, such as a Microsoft's notepad for writing and editing simple text. It may also consist of a collection of programs, often called a software package, which work together to accomplish a task, such as a spreadsheet package.
software designed to help the user to perform specific tasks
Examples of Application software are following:

• Payroll Software
• Student Record Software
• Inventory Management Software
• Income Tax Software
• Railways Reservation Software
• Microsoft Office Suite Software
• Microsoft Word
• Microsoft Excel
• Microsoft Powerpoint

Features of application software are as follows:

• Close to user
• Easy to design
• More interactive
• Slow in speed
• Generally written in high-level language
• Easy to understand
• Easy to manipulate and use
• Bigger in size and requires large storage space

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Computer software can be put into categories based on common function, type, or field of use. There are three broad classifications:

• Application software is the general designation of computer programs for performing tasks. Application software may be general purpose (word processing, web browsers,...) or have a specific purpose (accounting, truck scheduling, ..) Application software contrast with system software.
• System software is a generic term referring to the computer programs used to start and run computer systems including diverse application software and networks.
• Computer programming tools, such as compilers and linker, are used to translate and combine computer program source code and libraries into executable RAMs (programs that will belong to one of the three said)

Copyright status

The GNU Project categorizes software by copyright status: free software, open source software, public domain software, copylefted software, noncopylefted free software, lax permissive licensed software, GPL-covered software, the GNU operating system, GNU programs, GNU software, FSF-copyrighted GNU software, nonfree software, proprietary software, freeware, shareware, private software and commercial software.

Free software

Free software is software that comes with permission for anyone to use, copy and/or distribute, either verbatim or with modifications, either gratis or for a fee. In particular, this means that source code must be available. "If it's not source, it's not software." If a program is free, then it can potentially be included in a free operating system such as GNU, or free versions of the Linux system.
Free software in the sense of copyright license (and the GNU project) is a matter of freedom, not price. But proprietary software companies typically use the term "free software" to refer to price. Sometimes this means a binary copy can be obtained at no charge; sometimes this means a copy is bundled with a computer for sale at no additional charge.

Open source software

Open source software is software that is available free of charge. It can be used and disseminated at any point, the source code is open and can be modified as required. The one condition with this type of software is that when changes are made users should make these changes known to others. One of the key characteristics of open source software is that it is the shared intellectual property of all developers and users. The Linux operating system is one of the best known examples of open source software.

Copylefted software

Copylefted software is free software whose distribution terms ensure that all copies of all versions carry more or less the same distribution terms. This means, for instance, that copyleft licenses generally disallow others to add additional requirements to the software (though a limited set of safe added requirements can be allowed) and require making source code available. This shields the program, and its modified versions, from some of the common ways of making a program proprietary. Some copyleft licenses block other means of turning software proprietary.
Copyleft is a general concept. Copylefting an actual program requires a specific set of distribution terms. Different copyleft licenses are usually “incompatible” due to varying terms, which makes it illegal to merge the code using one license with the code using the other license. If two pieces of software use the same license, they are generally mergeable.

Non-copylefted free software

Noncopylefted free software comes from the author with permission to redistribute and modify and to add license restrictions.
If a program is free but not copylefted, then some copies or modified versions may not be free. A software company can compile the program, with or without modifications, and distribute the executable file as a proprietary software product. The X Window System illustrates this approach. The X Consortium releases X11 with distribution terms that make it noncopylefted free software. If you wish, you can get a copy which has those distribution terms and is free. However, nonfree versions are available and workstations and PC graphics boards for which nonfree versions are the only ones that work. The developers of X11 made X11 nonfree for a while; they were able to do this because others had contributed their code under the same noncopyleft license.

Shareware

Shareware is software that comes with permission to redistribute copies, but says that anyone who continues to use a copy is required to pay a license fee. Shareware is not free software, or even semifree. For most shareware, source code is not available; thus, the program cannot be modified. Shareware does not come with permission to make a copy and install it without paying a license fee, including for nonprofit activity.

Freeware

Like shareware, freeware is software available for download and distribution without any initial payment. Freeware never has an associated fee. Things like minor program updates and small gmes are commonly distributed as freeware. Though freeware is cost free, it is copyrighted, so other people can't market the software as their own.
There are several different types of system software that we will look at in more detail very shortly:

• Operating Systems are a collection of programs that make the computer hardware conveniently available to the user and also hide the complexities of the computer's operation. The Operating System (such as Windows 7 or Linux) interprets commands issued by application software (e.g. word processor and spreadsheets). The Operating System is also an interface between the application software and computer. Without the operating system, the application programs would be unable to communicate with the computer.

• Utility programs are small, powerful programs with a limited capability, they are usually operated by the user to maintain a smooth running of the computer system. Various examples include file management, diagnosing problems and finding out information about the computer etc. Notable examples of utility programs include copy, paste, delete, file searching, disk defragmenter, disk cleanup. However, there are also other types that can be separately installable from the Operating System

• Library programs are a compiled collection of subroutines (e.g. libraries make many functions and procedures available when you write a program)

• Translator software (Assembler, Compiler, Interpreter)

1. Assembler translates assembly language programs into machine code (A binary code that a machine can understand).
2. Compiler translates high level language code into object code (which is the machine language of the target machine).
3. Interpreter analyses and executes a high-level language program a line at a time. Execution will be slower than for the equivalent compiled code as the source code is analyzed line by line.