UWE - CSM - Control Structure Flowcharts

Three Programming Control Structures

SEQUENCE

SELECTION

ITERATION

See also: Programs are Algorithms and Modular Programming

Structure

Note that all programs are primarily

Sequences, - the statements in code are sequential (even when the sequences are run in parallel or concurrently).

Iteration

a given sequence is repeated

Selection (e.g. the If statement) means that program control may be transferred from one sequence to another sequence of instructions.

More precisely, we can say that the essential characteristic of structured code is

linearity of control

'Control' is passed from statement to statement sequentially.

Linearity of control requires that all program constructs have:

a single entry point and a single exit point

with only defined legal violations of these requirements (e.g. premature exit from an iteration - loop).

The following diagrams demonstrate the use of
Logic Flowcharts and Structured English to describe programming control structures.

Sequence

Selections - IF and CASE

Iterations - Loops

Tony Drewry

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