Choosing a computer

Press, 20 April 1982, Page 28

Choosing a computer

Choosing a computer? What size system should you be looking at? What peripherals will you need? The next few. articles in our series will address these issues. This week we categorise computer systems and describe the make-up of systems in each category. Future articles will develop this theme, discussing peripherals, software and costs. It is useful to start by categorising small computers. Then we can discuss the general characteristics of systems in each category. First, a disclaimer. Categorising and sizing computer systems are subjective activities. This article. presents just one view and the reader would be wise to keep an open mind until other opinions are solicited. We will avoid the terms personal computer, microcomputer and minicomputer in establishing our. categories. These terms have become fuzzy with changing technology and mean different things to different people. The minicomputers of the 1970 s are no more sophisticated than today’s microcomputers. ' We will instead categorise computer'systems as hobby systems, single-user professional systems and multiuser professional systems.

Hobby system purchased for the home

A hobby system is primarily purchased to provide computing in the home. It may be used to give the children computer awareness, to help with the tax return or to play computer games. '■ /Professional systems are used in the workplace. A

1 single-user system has one i screen and supports one user at a time. A multi-user system permits more than one screen to be connected. into : the computer, thus allowing more than one user to get . access to the computer at a time. . . Before purchasing a computer for professional use a .?■ buyer should attempt to forecast the workload for the machine. If more than one person will require access to the computer regularly, then a multi-user system is indicated. Note that in one configuration a particular brand of computer might .be a hobby system, but it can be upgraded to a system that would place it in one of the professional, categories. Also a computer syt em that has the capabilities of a professional system might be priced so well that it is popular as a hobby system. We do not need to be concerned about these anomalies. Our aim is to indicate the general characteristics of systems in different roles.' A computer system is made up of a number of components:, a central processing unit, memory, peri- • pherals and software. In most applications the components are chosen to suit the requirements of the application at a price that the application can justify. Surprisingly the choice of central processing unit is usually not an important factor in the suitability of a small computer for its intended application. The central processing units of today’s small computers are 8bit and 16-bit microprocessor chips that offer similar performance and characteristics. The central processing unit becomes more important in a multi-user system, where.

the computer is called upon to do more processing than in a single user system. In this case a faster or bigger processor is advantageous. Alternatively the system might contain a number of central processing units — possibly, with a dedicated central process'ing unit for each user.

The most important characteristics of a small computer are:

© Amount of storage for

data. © Speed of access to the data storage. © Amount of main memory. G Keyboard design. © Screen features.

© Sophistication of the system software. © Expandability.

Program and data storage

Any serious computer user will want to store programs and data on a storage medium. Otherwise the programs or data will have to be keyed in each time they are used! •

Popular storage media include cassettes, floppy discs, and hard discs. While floppy discs often prove sufficient for professional use where the amount of data to be stored is small or where frequent changing of floppy discs is acceptable, many

businesses will find that a hard disc is a good investment. Multi-user systems should be hard disc systems. Cassettes, which are slow compared to floppy discs, are suitable for the beginning hobby user but are not suitable for professional users. Hard. discs offer the fastest access to data but are the most expensive.

Memory to hold programs

Main memory is used on a computer to hold programs and data while an applica-

tion is being run. The hobbyist can start writing programs with-as little as IK bytes of memory, the more memory he has the bigger the programs he can write. Professional systems have at least 32K bytes of memory and usually have 64K bytes. A multi-user system will have more than this, dr might use separate microprocessors each with its own bank'of memory.

A keyboard on a professional machine will - be of superior construction. It will suit the requirements of a fast and fussy typist and will be able to stand up to many hours of continuous use.

Better keyboards have extra keys that can be used for special functions ■ and a calculator-style keypad. for fast entry of numeric data.

There is great variety in the screens used with computers. Television mohitors are acceptable on .hpbby sys--1 terns but ape not acceptable on professional systems. A screen for professional use should ideally display 80 characters across the screen and at least 20 lines down. Upper and lower case displays are preferable and are a necessity if the system is to be used for text processing or word processing. The system software provided with a computer will comprise an operating system, languages for writing programs and various utility programs. On a hobby system these might be combined into one product — the BASIC interpreter. Many single-user professional systems are implemented solely using a BASIC interpreter. More and more systems now sold, however, offer a full operating system (usually CP/M) and a variety of languages and utilities. ' A multi-user professional system will need a multi-..

user operating system, such as MP/M of Unix. A good professional system will use system software that is efficient, is user friendly, offers powerful programming facilities, offers a good file management system and has a range of useful utilities.

Any computer system should be capable of expansion, particularly professional systems. A hobbyist will eventually want to add more memory, a printer, or' a floppy disc. drive to his system. Any professional system must be capable of supporting additional disc storage. Professional systems should be able to be expanded with a range of hardware and software options.

Typical systems emerge

A picture should now be emerging on the make-up of a typical system in each category. A hobby system will cost from $3OO to $5OOO. A typical system might have 16K bytes of memory, a cassette interface for . data storage and a television monitor for a screen. Most programs are written in BASIC using a BASIC interpreter built into the system. A single-user professional system will cost from $5OOO to $20,000. It typically will have 64K bytes of memory, large capacity floppy discs or a small hard disc, a good screen and keyboard, a printer, and a versatile software environment.

A multi-user professional system will cost over $15,000. It will feature a multi-user operating system and at least five megabytes of hard disc storage.