Nascom News­let­ter

easier to use. The present generation of computers is much more ‘user friendly’, enabling almost anyone to become a computer user. This continuing improvement in the man-machine (person-machine?) interface can only serve to widen the acceptance of computers in everyday life.

The advent of the personal computer has made it possible for problems to be solved which would previously have been prohibitively expensive to solve by means of computers. However, the cost of computing is not the only obstacle to acceptance of computers, particularly in the area of the person-machine interface.

The solutions to the person-computer interface problem are now becoming more readily available – colour graphics and speech being areas which offer the most promise. Speech simulation is already available for the Nascom range of computers, although reliable speech recognition is still some way off. The ability to communicate to the computer user complex or simple results has always been a problem in the past, but now that high-quality colour graphics displays are available this hurdle can be crossed.

Colour graphics enables the computer to present information pictorially, which greatly improves the usability of programs. Sometimes information is difficult or impossible to present using only numbers and words, but becomes easily comprehensible in graphics form. Even computer output which does not require colour graphics to be usable will usually become clearer when converted to colour. The use of high-quality colour graphics is now open to all users, enabling business, scientific, engineering and other users to gain maximum efficiency.

The addition of quality colour graphics to the Nascom range of computers is achieved by means of the Advanced Video Controller (AVC). Equally important to the effective implementation of colour graphics is comprehensive and easy to use support software, and this is provided as standard with the AVC. Access to the colour graphics is made simple from either ROM BASIC or Extended BASIC (XBASIC), the latter being available for tape, NAS-DOS and CP/M users.

The principles of displaying a graphics picture are transparent to the user, but to gain a better understanding an insight into the theory of graphics in general will be useful.

The AVC works on the bit mapped raster which scan principle, which means that the computer can directly access and set the colour of any graphics point (known as pixel) on the display. This provides a much more flexible system than that allowed with a programmable character generator system. While programmable character generator (PCG) systems can offer faster graphics generation of a limited range of character shapes, they suffer severely from programming difficulties and the lack of generality of the pictures that they can represent. Normally they are limited to only 128, or possibly 256, special characters.