Some computer systems, especially some of the early ones, only did
one thing at a time. They had a list of instructions to carry out -
and these would be carried out, one after the other. This is called
a serial system.
Sometimes, if there was a lot of work to be done, then collections
of these instructions would be given to the computer to work on overnight.
Because the computer was working on batches of instructions the
type of operating system was called a Batch Operating System.
Batch operating systems are good at churning through large numbers
of repetitive jobs on large computers. Jobs like: working out the pay
of each employee in large firm; or processing all the questionnaire
forms in a large survey.