c语言for语言执行顺序

for(expr1; expr2; expr3)
{
statement;
}
next statement;

等同于：

expr1;
while(expr2)
{
statement
expr3;
}
next statement;

例如：

#include <stdio.h>
#include <string.h>

int main()
{
    unsigned long hval=0;
    char *key="alpha";
    char c;
    int i;

    for(i=1;(c=*key++)!=0;i++)
    {
        printf("c is %d\n",c);
        hval+=c*i;
        printf("hval is %ld\n",hval);
    }
}