SYSTEM SOFTWARE

Computers use a series of control programs, called the operating systems, that moves data in and out of main memory and monitors the running of application programs.
The operating system is the primary component of system software. Some computers have built-in operating system, but these cannot be easily changed or updated.

Most computer manufacturers either provide their own operating system, usually on disk, or allow users to purchase disks containing the more popular operating systems.

Operating systems interact with users by means of a user interface. Some operating systems, especially those for larger computer systems, are text based and require the user to learn a set of commands (command line interface)

Some operating systems for PCs like the Macintosh operating systems, permit users to select commands from graphic symbols, or icons, displayed on the screen. Text-based operating systems, like DOS (Disk Operating System) for IBM and IBM compatibles computers, can work in conjunction with graphical user interfaces like windows, which make them easier to use or more user friendly.

APPLICATION SOFTWARE

Application programs are designed to satisfy user needs by operating on input data to perform a given job, for example, to prepare a report, update a master payroll file, or print customer bills.

Typically, application programs are acquired in one of two ways; Package programs purchased off-the-shelf from a software retailer or; Custom programs designed especially for the unique needs of an individual or an organization

Packaged programs allow limited customization, but they really are intended to be used as is by a broad range of users. Although they may not meet all aspects of every users need, application packages are inexpensive compared to custom programs and are supplied with comprehensive user reference manuals called documentation.

Custom software, on the other hand, is written by programmers within an organization, by outside consultants, or by self-employed programmers. Custom programs are designed to meet the precise needs of users, but they are very time consuming and costly to develop.
THE COMPUTER GENERATIONS

Since the 1940’s, four generations of computers have evolved. From the first to the fourth, the trend has been to produce more powerful, less expensive, smaller and more reliable computer systems.

First generation

The first commercial electronic computer was UNIVAC 1 (Universal Automatic Computer). This machine was developed specifically for scientific and military purposes, but was dedicated to business data processing applications.

The characteristic that distinguished first generation computers from subsequent machines was the use of vacuum tubes to control internal operations. Vacuum tube un-reliable, generate a lot of heat, required air-conditioning system.

Binary notation was used instead of decimal notation. All instructions and information were stored in the computer as 1s and 0s, which corresponds to the electronic conditions ‘on’ and ‘off’.

Drawbacks:

They took several minutes to ‘warm up”. When they were completely warmed up, they became quite hot. Early computers used thousands of vacuum tubes. They occupied the whole rooms and required an enormous amount of electric current to keep them going.

Second generation

In the late 1950s, tiny, solid-state transistors replaced vacuum tubes in computers. The elimination of vacuum tubes greatly reduces generated heat and made possible the reduction in the size of the developed computers.

This generation of computer also uses magnetic cores for representing data in computer. Because cores were far smaller than vacuum tubes, internal storage capacity becomes greater even though the actual size of second generation computers was sharply reduced.

As about the same time, in the early 1960’s, magnetic tape and disks began to be widely used by auxiliary storage. As a result of these developments, a significant increase in the speed and processing capability of computers was achieved.