以下是一个C语言的数值交换代码示例：
#include <stdio.h>
void swap(int *a, int *b) {int temp = *a;*a = *b;*b = temp;}
int main() {int num1 = 10;int num2 = 20;
printf("交换前：\n");printf("num1 = %d\n", num1);printf("num2 = %d\n", num2);swap(&num1, &num2);printf("\n交换后：\n");printf("num1 = %d\n", num1);printf("num2 = %d\n", num2);return 0;}
运行结果为：交换前：num1 = 10num2 = 20
交换后：num1 = 20num2 = 10
