10 
makes the present microcomputers considerably slower (3 to 10x) than 
minicomputers. However, this is not necessarily a disadvantage, as the speed 
requirements are usually not extremely high. By using PROM’s (i.e. Program- 
mable Real Only Memories) data processing and controls can be changed and 
thus adapted to specific needs. For data storage and retrieval inexpensive 
RAM ’s (Random Access Memories, i.e. read/write memories) are used. The 
storages are expandable. Microcomputers can easily be adapted to monitor 
different peripheral units, i.e. carriages, displays and recording devices. 
III-4 Recording devices € e" 
Recording devices have been classified into three categories: digital, 
symbolic-graphical and photographic. Some recording devices are often 
delivered as standard peripherals of a digital computer (10). The commonly 
used digital recording units are: 
— paper tape or card punch 
— magnetic tape unit or cassette 
— magnetic disk unit or Floppy Disk 
— typewriter — ) 
— teletype ) may also serve for semi-graphical recording 
— line printer ) 
A recording process can be controlled either by means of hardwired circuits 
or by a computer programme. 
In dynamic operation the recording speed plays an important role. The 
speed should be higher than, or equal to, the maximum rate of data output. 
The rate can be reduced by compressing the data prior to recording. In dynamic 
operation it can be distinguished between recording by constant increments 6 e 
in time, in path (or in co-ordinates) or by a combination of both. 
For symbolic-graphical recording (e.g. of line maps) different types of 
automatic drafting machines can be used. These may also operate off-line, i.e. 
independently of other components. The same applies to digitally controlled 
orthophoto printers. 
IV Software 
The software depends on tasks a system should perform, on equipment