Categories and Characteristics of Software Systems

Categories of s/w :-

There are two main types of software: systems software and application software.

1. System Software: System software or operating system is the software used by the computer to translate inputs from various sources into a language which a machine can understand. Basically, the OS coordinates the different hardware components of a computer. There are many OS in the market. The most popular Os are from the stable of Microsoft. We have all heard, used and wondered at the Windows software, which is an OS. Starting with Windows, Microsoft has migrated to Vista, its latest offering in the market. It may come as a surprise to some that there are other operating systems used by others. Among these UNIX is used for large office setups with extensive networking. XENIX is software which has now become redundant. HP -UX and AIX are some operating systems used by HP computers. Apache OS is quite popular with web servers. IBM still uses proprietary operating systems for its main frames. Proprietary systems are generally built with the help of a variant of UNIX operating system.

System software is a software that provides platform to other softwares. Some examples can be operating systems, antivirus softwares, disk formating softwares, Computer language translators etc. These are commonly prepared by the computer manufacturers. These softwares consists of programs written in low-level languages, used to interact with the hardware at a very basic level. System software serves as the interface between the hardware and the end users.

The most important features of system software include :
1. Closeness to the system
2. Fast speed
3. Difficult to manipulate
4. Written in low level language
5. Difficult to design

2. Application software: A normal user rarely gets to see the operating system or to work with it. But all of us are familiar with application software which we must use to interact with a computer. Popular examples of application software are the Microsoft office suite which includes Word, Excel and PowerPoint. We have used these applications extensively. Internet explorer, Mozilla Firefox is two applications used to access the internet. E-mail software like Outlook express is used to manage Emails. It is obvious that all software utilized for working on a computer is classified as application software. In fact all user interfaces are an application. The anti-virus is an application and so is the Media player.

Characteristics of s/w :-

A good s/w system has to maintain following characteristics:

1. Operational Characteristics
2. Transition Characteristics
3. Revision Characteristics

1. Operational Characteristics:- These are functionality based factors and related to exterior quality of s/w.

• Correctness
• Usability/learnability:- The amount of time required to learn how to use the s/w should be less.
• Reliability:- Less failure
• Security:- S/w should secure from external threats.
• Safety:- The s/w should not be hazardous to the environment/life.

2. Transition Characteristics:- 

• Interoperability:- Ability of software to exchange information with other application.
• Reusability:- Reuse s/w codes with some modification for different purpose.
• Portability:- Ability of s/w to perform same function across all environment and platforms.

Revision Characteristics:-

• Maintainability
• Flexible:- Changes should be easy
• Scalability:- Easy to upgrade i.e for more work for more no. of users.
• Testability:- Easy testing
• Modularity:- S/w should be made of units & modules.