#include<stdio.h>int main(){int num=0;printf("請輸入一個數:\n");scanf("%d",&num);int i=2,a=0;for(i;i<num;i++){if(num%i==0)a++;}if(a==0){printf("%d是素數.\n",num);}else{printf("%d不是素數.\n",num);}return 0;}警告信息:||=== Build: Debug in practice (compiler: GNU GCC Compiler) ===|E:\c++\practice\main.cpp||In function 'int main()':|E:\c++\practice\main.cpp|8|warning: statement has no effect [-Wunused-value]|||=== Build finished: 0 error(s), 1 warning(s) (0 minute(s), 1 second(s)) ===|