The output from a microprocessor is digital. Most control elements
require an analogue input and so the digital output from a
microprocessor has to be converted into an analogue form before it can
be used by them. The input to a digital-to-analogue converter is a binary
word and the output its equivalent analogue value. For example, if we
have a full scale output of 7 V then a digital input of 000 will give 0 V,
001 give 1 V .... and 111 the full scale value of 7 V. Figure 1.41
illustrates this.