Abstract: Minicomputer including a computing unit, numeral, function and clearing inputs, a fixed-program memory and selectively freely-programmable memories, and a readout or display unit including a selector switch for calculating and converting in two systems of units selectively connectible to the fixed-program memory and the computing unit, the fixed-program memory having means for storing and reading out conversion factors and, selectively inverse values thereof as well as a corresponding dimension, the fixed-program memory having a respective input connected to a factor selection unit and to a call-up unit for the dimension of the respective selected factor and inverse value, and having a respective output connected to the computing unit and to the readout or display unit.