问返回类型为0吗？或者这里发生了什么？

EN

#include <stdio.h>
#include <ctype.h>

void printSquare( char c, int size);

int main(){

    int userNum;
    char userChar;

    printf("Enter a character : \n");
    scanf("%s",&userChar);

    while(isalpha(userChar) == 0){
        printf("Enter a character : \n");
        scanf("%s",&userChar);
    }

    printf("Enter a number(3-10) : \n");
    scanf("%d",&userNum);

    while(isdigit(userNum) == 0){
        printf("Enter a number(3-10) : \n");
        scanf("%d",&userNum);
    }   

    printSquare(userChar,userNum);

}

void printSquare( char c, int size){
    char letters[27] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    int initChar;

    for (int i = 0; i < sizeof(letters)/sizeof(letters[i]); i++)
    {
        if (c == letters[i])
        {
            initChar = i;
            printf("FOUND IT - > %c\n",letters[i]);
        }
    }

    for (int i = 0; i < size; i++)
    {
        for (int j = initChar; j <  initChar + size; j++)
        {
            printf("%c",letters[j % 27] );
        }
        printf("\n");
        initChar+=1;
    }
}