Computers appropriate for small-to-medium sized businesses (such as large farms, agri-businesses, and management and production consultants) can be broadly classified into three groups: pocket sized programmable calculators (£50-£500); micro-computers (£500-£5000); mini-computers (£5000-£50000). There are also the main-frame computers which take up considerably more resources of both money and space. Main-frame computers are likely to be restricted for use in specialist functions such as the handling of very large programs, complex statistical packages and so on.

Of these, the simplest type to operate allows specific programs to be written onto magnetic cards which are fed in as required. Such programs may calculate: nutrient requirements for given levels of production; nutritional quality of a combination of ingredients in a farm mix; average herd performances to date; a register of input and output for the unit; and the like. The capacity of these machines is limited, both as to the extent and complexity of the calculations allowed and to the volume of data which can be stored and executed. The alphabetic printing and layout capability is rather poor and the user must be familiar with the input format and with the configuration for the output.