编函数void fun(char *tt,int pp[ ]),统计tt在字符串中a到z字母出现的次数由pp数组传回main 函数

#include <stdio.h>
#include <string.h>
void fun(char *tt, int pp[])
{
char ch;
int i=0;
do
{
ch=tt[i];
ch=tolower(ch);
pp[ch-'a']++;
i++;
}while(ch!='\0');

}

int main()
{
char aa[1000] ;
int bb[26]={0}, k, n ;
printf( "\nPlease enter a char string:" ) ; scanf("%s", aa) ;
fun(aa, bb ) ;
for ( k = 0 ; k < 26 ; k++ ) printf ("%d ", bb[k]) ;
printf( "\n" ) ;
return 0;
}