格式符什么时候在需要打？？？
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首先你要理解什么是格式符，C语言中常用的格式符有哪些?
例：%s字符串 %d十进制数字 %\p地址 %f浮点数
在printf里格式化输出是要一个变量替换的作用，举例如下
int main(){
int num = 20;
float flo = 13.5;
char str[30] = "my name is frind";
printf("%d,%f,%s",num,flo,str);
}
输出为:20 13.5 my name is frind不一定啊，比如：
#include<stdio.h>
{
void main()
{
printf("Hello World!!");
}
}这里就没有用格式符。