C语言英文课件7：函数.pptVIP

Chapter 7 Functions(函数) 7.1 Foundation of Functions 7.2 Nested Calling and Recursive Calling 7.3 Arrays Qua Parameters of Functions 7.4 The Scope of Variables 7.5 The Storage Type of Variables 7.6 Local Functions and External Functions 7.1 Foundation of Functions DECLARATIONS OF FUNCTIONS 2. A program is just a set of definitions of variables and functions. [ex.7.3] output all of primes between 2and200 main(){ int i, j, counter=0;  for(i=2 ; i=200; i++) { for(j=2; j=i-1; j++) if(i%j==0) break; if( j == i ) { printf(“%8d”,i);  counter++;  } } printf(“\ncounter=%d\n”,counter); } 7.1.2 Returning Values and Types of Functions Return statement forma: return ( expression ); The return statement is the mechanism for returning a value from the called function to its caller. Any expression can follow return: return expression; The expression will be converted to the return type of the function if necessary. Parentheses are often used around the expression, but they are optional. 7.1.3 Declaration of Called Function and prototype(原型） of Function 当被调函数为自定义函数，且与主调函数在同一程序文件中时，要在主调函数中对被调函数作声明。 Declaration form the head of function+semicolon When function declaration can be left out (1)definition of the called function before the calling function； (2) delaration all functions before definition; (3)type of functin and type of parameters are all int 7.1.4 Call a Function Calling form： function name( [actual Parameters list] ) Calling mode： (1) In expression ex. ave=(sum(a)-max(a)-min(a))/n; m=max(n3, max(n1,n2) ); printf(“%d”,max(n1,n2)); (2) Function statement (function type is void) ex. printline(); 7.1.5 Formal Parameters and Actual Parameters