Repeat a sound four times a measure.

Computers are good at repetitive tasks: they exactly follow instructions and perform them quickly. But if the programmer has to write the same instructions for every repetition, they waste time and increase the chances of a mistake.

In our example, instead of literally writing “play a sound, play a sound, play a sound, play a sound”, programmers can use a loop structure. A loop is a sequence of instructions which is specified once but which may be carried out several times in a row. In this case there is one instruction (play a sound) and it should be carried out 4 times.

Loop structures can also specify that the instructions are repeated until a certain condition is met. For example, “Repeat a sound until you are booed off stage”.