标准输入流输出流以及错误流

#include <stdio.h>

int main()
{
	//printf("please input the value a:\n");
	fprintf(stdout, "please input the value a:\n");
	int a;
	//scanf("%d",&a);
	fscanf(stdin,"%d",&a);
	if(a<0){
		fprintf(stderr, "the value must > 0\n");
		return 1;
	}

	return 0;
}