带注释

#include <stdio.h>   //头文件
int main(void)   //主函数无参数，返回的值是整数
{long num;   //定义了一个长整型变量numlong sum=0L;   //定义了一个长整型变量sum，把sum初始化为long类型的0printf("Please input an integer to sum up. End with the letter f\nYou can input and press Enter:");   //提示用户输入整数来求和，以f结束（其实输入任何非数值的数也可以做到）while(1==scanf("%d",&num))   //若scanf()读取到了整数就将其存入num中并返回1，再判断是否与1相等，相等，循环；若scanf()读取不成功（用户输入的非数字）就返回0，再判断是否与1相等，不相等，循环结束{sum+=num;   //sum=sum+num，求和printf("You can input and press Enter:");   //可以继续输入}printf("\nSo let's calculate the sum:%ld\n",sum);   //求和结果以长整型格式输出return 0;   //返回语句
}

不带注释

#include <stdio.h>
int main(void)
{long num;long sum=0L;printf("Please input an integer to sum up. End with the letter f\nYou can input and press Enter:");while(1==scanf("%d",&num)){sum+=num; printf("You can input and press Enter:");}printf("\nSo let's calculate the sum:%ld\n",sum);return 0;
}

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