《C语言课程设计案例精编》课件 3.pptVIP

Example_3.9: Output below character string: a z b y c x d w e v f u g t h s i r j q k p l o m n Analyze: odd-bit: char is from ‘a’ to ‘m’ to increment; even-bit: char is from ‘z’ to ‘n’ to decrement. #include stdio.h main() { char i , j ; /* i is odd-bit char, j is even-bit char */ for ( i= ‘a’ , j= ‘z’ ; i j ; i++, j-- ) printf(“ %c %c ”, i, j); /* at one time, output two char */ printf(“\n”); } for (cont.) In for statement, comma, works as operator, not separator! Parallel-loop structure!!! 并列循环结构 3.3 Iteration statements (Summary) C language supplies three kinds of loop statements: while, for and do-while. for and while first judge loop condition then execute loop body; do-while first execute loop body then judge loop condition. loop condition expression is 1 for while and do-while, but there are 3 expressions for for loop。 while、do-while、for can be replaced by each other 。 While is always used when initialization is not necessary or loop times is not sure; on contrary, for is always used；do-while is used to loop executed at least once. Loop statements can be nested, loop can be parallel, but can not be intercrossed(交叉). 3.4 Jump Statements and Labeled Statements Jump statements transfer control unconditionally, which include: Labeled statements may carry label prefixes, which include: Jump Statements break continue return goto Labeled Statements identifier case default Break, Continue and Return The form of break statement: break ; Function introduce: A break statement provides an early exit from the innermost enclosing loop or switch. It may appear only in an iteration statement (while, for and do-while) or a switch statement. Expr? break; Expr? break; expr2? break; expr3; expr1; Statement after loop Statement after loop Statement after loop Break, Continue and Return (cont.) How to use break in loop structure: N Y N