1. Pass value parameter (not pointer parameter):
#include <stdio.h>
int inc(int x);
int main(void)
{
int num = 1;
printf("%d\n",inc(num)); /* 2 */
printf("%d\n",num); /* 1; num 并没有改变,用作函数参数时只是复制过去 */
getchar();
return 0;
}
int inc(int x) {
x++;
return x;
}
2. Address: Parameters are pointers, parameters are addresses
#include <stdio.h>
int inc(int *p);
int main(void)
{
int num = 1;
printf("%d\n",inc(&num)); /* 2 */
printf("%d\n",num); /* 2; num 已被修改 */
getchar();
return 0;
}
int inc(int *p) {
*p = *p + 1; /* 通过地址修改了值 */
return *p;
}
3. Examples to address but not be modified:
#include <stdio.h>
int inc(int *p);
int main(void)
{
int num = 1;
printf("%d\n",inc(&num)); /* 2 */
printf("%d\n",num); /* 1 */
/* 虽然函数是传址,但这里的 num 并没有改变; 因为下面的函数中并没有给指针赋值 */
getchar();
return 0;
}
int inc(int *p) {
return *p + 1;
}
4. Formal participation in the actual parameter:
It's just not much of a name, like in the following example
X and Y are the formal parameters of the SUM function;
I and 22 are arguments to the SUM function.
#include <stdio.h>
int sum(int x,int y);
int main(void)
{
int i = 11;
i = sum(i,22);
printf("%d\n",i);
getchar();
return 0;
}
int sum(int x,int y) {
return x + y;
}
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