c语言基础教程英文版ch05.pptxVIP

A First Book of ANSI CFourth EditionChapter 5RepetitionObjectivesBasic Loop StructuresThe while StatementComputing Sums and Averages Using a while LoopThe for StatementA First Book of ANSI C, Fourth EditionObjectives (continued)Case Studies: Loop Programming TechniquesNested LoopsThe do-while StatementCommon Programming and Compiler ErrorsA First Book of ANSI C, Fourth EditionIntroductionA section of code that is repeated is called a loop, because after the last statement in the code is executed, the program branches, or loops, back to the first statement and starts another repetition through the codeEach repetition is also called an iteration or pass through the loopA First Book of ANSI C, Fourth EditionBasic Loop StructuresConstructing a repeating section of code requires that four elements be present:Repetition statementwhile statementfor statementdo-while statementConditionA statement that initially sets the condition being testedA statement within the repeating section of code that alters the condition so that it eventually becomes falseA First Book of ANSI C, Fourth EditionPretest and Posttest LoopsA First Book of ANSI C, Fourth EditionPretest and Posttest Loops (continued)A First Book of ANSI C, Fourth EditionCounter-Controlled and Condition-Controlled LoopsCounter-controlled loop: the condition is used to keep track of the number of repetitionsAlso known as a fixed-count loopCondition-controlled loop: the tested condition does not depend on a count being achieved, but rather on a specific value being encounteredA First Book of ANSI C, Fourth EditionBasic Loop StructuresA First Book of ANSI C, Fourth EditionThe while StatementThe general form of the while statement iswhile (expression) statement;The transfer of control back to the start of a while statement to reevaluate the expression is known as a program loopThe following is a valid but infinite loop:while (count = 10) printf(%d ,count);A First Book of ANSI C, Fourth EditionThe while Statement (con