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level: Chapter 5 - Rule of thumb

Questions and Answers List

level questions: Chapter 5 - Rule of thumb

QuestionAnswer
What are the key factors of structured programming?• Simple building blocks whose individual correctness can be easily proven •Well-defined rules that enable correct assembly of these building blocks
Structured programming - Rule of thumb•No »free« jump statements (»Goto considerd harmful« – Edsger Dijkstra, 1968) •Each loop has exactly one entry and exactly one exit point (➝ no break) • Statements should have exactly one effect (no »side effects«) • In multiway branches (switch) always exactly one path should be traversed (➝ no sequential continuation, always specify default clause)
Structured programming - Rule of thumb (2)• Subroutines communicate with each other exclusively via parameters and function values (or via class and instance variables – see later) and not via shared, global data structures • A subroutine should also be documented as precisely as possible (ideally formally), in particular: • the effect mentioned above (»postcondition of the subroutine«) • the conditions that must be met for the subroutine to be able to achieve this effect (»precondition of the subroutine«)