结构化编程-Structured programming

结构话编程强调的是对流程的控制；

它为面向过程编程提供天然的支持。

Structured programming is a programming paradigm aimed at improving the clarity, quality, and development time of a computer program by making extensive use of subroutines, block structures, for and while loops—in contrast to using simple tests and jumps such as the go to statement, which could lead to "spaghetti code" that is difficult to follow and maintain.

Control structures[edit]

Following the structured program theorem, all programs are seen as composed of control structures:

• "Sequence"; ordered statements or subroutines executed in sequence.
• "Selection"; one or a number of statements is executed depending on the state of the program. This is usually expressed with keywords such as if..then..else..endif.
• "Iteration"; a statement or block is executed until the program reaches a certain state, or operations have been applied to every element of a collection. This is usually expressed with keywords such as while, repeat, for or do..until. Often it is recommended that each loop should only have one entry point (and in the original structural programming, also only one exit point, and a few languages enforce this).
• "Recursion"; a statement is executed by repeatedly calling itself until termination conditions are met. While similar in practice to iterative loops, recursive loops may be more computationally efficient, and are implemented differently as a cascading stack.

 

Graphical representation of the three basic patterns — sequence, selection, and repetition — using NS diagrams (blue) and flow charts (green).

Subroutines[edit]

Subroutines; callable units such as procedures, functions, methods, or subprograms are used to allow a sequence to be referred to by a single statement.

Blocks[edit]

Blocks are used to enable groups of statements to be treated as if they were one statement. Block-structured languages have a syntax for enclosing structures in some formal way, such as an if-statement bracketed by if..fias in ALGOL 68, or a code section bracketed by BEGIN..END, as in PL/I, whitespace indentation as in Python - or the curly braces {...} of C and many later languages.

https://en.wikipedia.org/wiki/Structured_programming