实参与形参的定义.以及关系,,

实参与形参的定义.以及关系,,

实参
全称为"实际参数"是在调用时传递该函数的参数.
实参可以是常量、变量、表达式、函数等,无论实参是何种类型的量,在进行函数调用时,它们都必须具有确定的值,以便把这些值传送给形参.因此应预先用赋值,输入等办法使实参获得确定值.
形参
全称为"形式参数"是在定义函数名和函数体的时候使用的参数,目的是用来接收调用该函数时传递的参数.
形参的作用是实现主调函数与被调函数之间的联系,通常将函数所处理的数据,影响函数功能的因素或者函数处理的结果作为形参.没有形参的函数在形参表的位置应该写void.main 函数也可以有形参和返回值,其形参也称为命令行参数,由操作系统在启动程序时初始化,其返回值传递给操作系统.
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实例1：
定义函数时函数名后面括号内的表达式称为形式参数（简称"形参"）,被调函数名后面括号中的表达式称为实际参数（简称"实参"）.
int abc(int a,int b) //int a,int b 就是"形参"
{
int c=a+b;
return c;}
－－－－－－－－－－－
int i =abcd(10,20); //10,20就是实参
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实例2：
main( )
{ int a,b,c;
scanf("%d%d",&a,&b);
c=max(a,b);
printf("max is %d",c);
}
max(int x,int y) /*定义有参函数max*/
{ int z;
z=x>y?x:y;
return(z);
}
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其中x,y为形参,a,b为实参;
注意:C语言规定,实参变量对形参变量的数据传递是"值传递",即单向传递,只由实参传给形参
,而不能由形参传回来给实参.