system ("pause")这句话在编译的时候为什么无法通过?
程序代码:
#include <stdio.h> int main (void) { int n = 10; printf ("Initially, n = %d\n", n); for (int n = 1; n < 3; n++) printf ("loop 1: n = %d\n", n); printf ("After loop 1, n = %d\n", n); for (int n = 1; n < 3; n++) { printf ("loop 2 index n = %d\n", n); int n = 30; printf ("loop 2: n = %d\n", n); n++; } printf ("After loop 2, n = %d\n", n); system ("pause"); return 0; }我用 gcc -std=c99 -o 12_forc99.exe 12_forc99.c出现
12_forc99.c: In function 'main':
12_forc99.c:19:2: warning: implicit declaration of function 'system' [-Wimplicit-function-declaration]
system ("pause");
^
这样的错误提示,把system ("pause");注销后一切正常,这句话有什么问题吗?为什么编译无法通过?