Computer systems consist in part of hardware that controls the overall activity of the computer. But in order for hardware to function, it must have the necessary instructions. These instructions are supplied by software. There are different kinds of software, each of which serves a specified purpose. Some software is necessary to make the computer operate. Another kind enables the computer to perform specific tasks. Still other software exists solely for entertainment purposes.

OPERATING SYSTEM SOFTWARE

The operating system software makes the computer perform its basic operational functions. Disk operating system (DOS) is one of the earlier types of operating system software used to power IBM-compatible computers. Commands are typed at a prompt to direct the computer to carry out its functions.

Windows is the most common operating system today. It permits several programs to be opened simultaneously and provides ease of movement between the open programs.

Windows NT is used for business networks. Once this operating system is downloaded and running, other kinds of software are opened to perform the desired functions.

The Macintosh Operating System (Mac OS) is designed for use with Apple, Mac, and Power Mac computers. One disadvantage of Mac OS is that fewer programs have been written for it compared to the number written for DOS or Windows.

APPLICATION SOFTWARE

Application software allows performance of specific tasks, such as writing letters, computing formulas, playing games, or carrying out desktop publishing tasks

• Word-processing software: Writing tasks previously done on typewriters with considerable effort can now be easily completed with word-processing software. Writing tasks such as keying in reports, letters, and tables, as well as merging documents, can be performed easily. Documents can be easily edited and formatted. Revisions can be made by deleting (cutting), inserting, moving (cutting and pasting), and copying data. Documents can be stored (saved) and opened again for revisions and/or printing. Many styles and sizes of fonts are available to make the document attractive.
• Spreadsheet software: Spreadsheet software permits performance of an almost endless variety of quantitative tasks such as budgeting, keeping track of inventory, preparing financial reports, or manipulating numbers in any fashion, such as averaging each of ten departmental monthly sales over a six-month period. A spreadsheet contains cells, the intersection of rows and columns. Each cell contains a value keyed in by the user. Cells also contain formulas with many capabilities, such as adding, multiplying, dividing, subtracting, averaging, or even counting. An outstanding feature is a spreadsheet's ability to recalculate automatically. If one were preparing a budget, for example, and wanted to change a variable such as an increase in salary or a change in amount of car payments, the formulas would automatically recalculate the affected items and the totals.
• Database software: A database contains a list of information items that are similar in format and/or nature. An example is a phone book that lists a name, address, and phone number for each entry. Once stored in a database, information can be retrieved in several ways, using reports and queries. For example, all the names listed for a given area code could be printed out and used for a commercial mailing to that area.
• Desktop publishing software: This software permits the user to prepare documents by using both word-processing devices and graphics. Desktop publishing software uses word-processing software, with all its ease of entering and revising data, and supplements it with sophisticated visual features that stem from graphics software. For example, one can enhance a printed message with virtually any kind of illustration, such as drawings, paintings, and photographs.
• Presentation software: A speaker may use presentation software to organize a slide show for an audience. Text, graphics, sound, and movies can easily be included in the presentation. An added feature is that the slide show may be enhanced by inclusion of handouts with two to six slides printed on a page. The page may be organized to provide space for notes to be written in by the audience as the presentation ensues. An example of this is Power Point. Preparation of the software is simplified by the use of 'wizards' that walk the user through the creation of the presentation.
• Office suite software: Office suite software puts together complete programs of software. A typical suite package might include word processing, spreadsheet, databases, and presentation software. Depending on the jobs that need to be done, the suite provides the tools to make professional-looking documents.

Each piece of software works independently as well as with other parts of the suite. Items on the menu bar —such as File, Insert, and Format —work similarly on all the programs in a suite. Thus, familiarity with one program makes it easy to work with the other programs.

A typical example of office suite software is mail sent via bulk rate. It is usually addressed by name to an individual, rather than to "Occupant," with names and addresses accessed from the database memory. Merging those names with the letter in the word processor produces a form letter. A spreadsheet might also have been used to include charts and graphs with the letter. When completed, all forms are inserted into envelopes addressed by means of the database and word processor.

COMMUNICATIONS SOFTWARE

Using telephone lines and working through the computer's modem, communications software makes it possible to communicate to any location in the world using either fax or electronic mail. A fax transmits whatever copy is on an original sheet of paper (text, graphics, or handwriting) to another computer or fax machine. Electronic mail (e-mail) is a text message. It remains in the receiver's computer until retrieved. The message can be stored in either the sender's or the receiver's computer for later processing. Attachments or files can also be sent via e-mail.

UTILITY SOFTWARE

Utility software is used to diagnose computer problems and repair them. A major type is a virus (or "illness") checker. It checks for viruses the computer may have received from downloading information received from the Internet, e-mail, or another disk. Although some viruses may do little damage, others can cause serious damage to files and/or the computer operating system. It is important for a computer owner to find a virus-check program, install it, use it, and keep it continually updated. New viruses are found continually, and the only way to be safe is to update. Some antivirus software allows easy updating by downloading new files from the Internet.

EDUCATIONAL SOFTWARE

By teaching by means of games, educational soft ware is designed to make learning fun. The approach used in educational software is that of a tutorial in which the learner competes with him or herself. Such software appeals to persons of all ages but particularly to young children, who can learn skills related to reading and arithmetic. Older children and adults can learn or improve on a wide variety of more mature skills.

SPECIAL SOFTWARE ACQUISITION ARRANGEMENTS

Some kinds of software are given away. Another kind permits the potential user to try the software before purchasing it. Freeware software is free for those who ask, but the rights remain with the developer. Public domain software is free to the user without any copyright or other restrictions. Shareware software permits potential buyers to try out the software. A user who likes it may purchase it by sending payment to the developer. The developer in turn may send the buyer sup porting materials and information.

SUMMARY

Software is as critical to computers as breathing is to humans. Fortunately, an extremely wide variety of software programs are available that make possible the preparation of virtually any kind of computer product.