improving the clarity, quality, and development time of a computer program by making extensive use of the structured control flow constructs of selection (if/then/else) and repetition (while and for), block structures, and subroutines.
The structured program theorem provides the theoretical basis of structured programming.
It states that three ways of combining programs—sequencing, selection, and iteration—are sufficient to express any computable function.
This observation did not originate with the structured programming movement; these structures are sufficient to describe the instruction cycle of a central processing unit, as well as the operation of a Turing machine.