执行1+2+3+4+5.。。+100？5050 ？

while语句

#include <stdio.h>
int main(){
	int a=1,sum=0;
	while(a<=100){
		sum=sum+a;
		a++; 
	}
	printf("%d",sum);
}

do-while语句

#include <stdio.h>
int main(){
	int a=1,sum=0;
	do{
		sum=sum+a;
		a++;
	}while(a<=100);
	printf("%d",sum);
} 

for语句

#include <stdio.h>
int main(){
	int a,sum;
	for(a=1,sum=0;a<=100;a++){
		sum=sum+a;	
	}
	printf("%d",sum);
}