C lang: Pointer

Ax_Terminology

xa_pointer

pointer is the address used to store the variable;A variable (or data object) whose value is a memory address

Bx_Operator

xa_indirection operator(*)

xb_address operator(&)

Cx_Program

xa_not use pointer

#include <stdio.h>
void verse(int u,int k);
//// main function ////
int main(void)
{
    int a = 1, b = 10;
    printf("one : %d %d\n",a ,b);
    verse(a, b);
    printf("one : %d %d\n",a ,b);
    return 0;
}
//// exchange function ////
void verse(int u,int k)
{
    int o;
    printf("%d %d\n", u, k);
    o = u;
    u = k;
    k = o;
    printf("%d %d\n", u, k);
}
//one do not exchange

xb_use pointer

#include <stdio.h>
void verse(int * u, int * y);
//// main  ////
int main(void)
{
    int x = 5, y = 10;
    printf("before x >> %d      y >> %d\n", x, y);
    verse(&x, &y);
    printf("now x >> %d      y >> %d\n", x, y);
    return 0;
}
//// exchange  /////
void verse(int * u, int * y)
{
    int odd;
    odd = *u;
    *u = *y;
    *y = odd;
}