C 布尔类型函数总是返回 FALSE

Question

My assignment is to make a program that takes a string and output:

the number of characters in the string
the number of vowels in the string
the number of UPPERCASE letters in the string
the number of lowercase letters in the string
the number of other characters in the string

We are not allowed to use the ctype.h library. Right now I'm just trying to output the number of vowels.

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

bool isVowel(char *c);

int main(){
    char userString[5];
    int i;
    int vowelCount;
    char *c;
        printf("enter string:");
        scanf("%c", userString);
            for(i=0; i<= 4; ++i){
                userString[i] = *c;
                isVowel(c);
                if(isVowel(c)){
                    vowelCount = vowelCount + 1;
                }
            }
    printf("%d\n", vowelCount);
return 0;
}

bool isVowel(char *c){
    if(*c == 'a' || *c == 'A' || *c == 'e' || *c == 'E' || *c == 'i' || *c 
== 'I' || *c == 'o' || *c == 'O' || *c == 'u' || *c == 'U' ){
        return true;
    }
    else{
        return false;
    }
}

I believe that isVowel is always returning false because, when I run it with the input "test!",I get this:

enter string: test!
0

Answer 1

You're not setting the c variable. I suspect this line:

userString[i] = *c;

should be something like:

c = userString + i;

Answer 2

This is your code with some corrections:

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

bool isVowel(char c);

int main(){
    char userString[5];
    int i;
    int vowelCount=0;
    char c;
        printf("enter string:");
        scanf("%s", userString); // %s
            for(i=0; i<= 4; ++i){
                c=userString[i] ;              
              printf("%c",c);

                if(isVowel(c)){
                    vowelCount = vowelCount + 1;
                } 
            }
    printf("%d\n", vowelCount);
return 0;
}

bool isVowel(char c){
    return (c == 'a' || c == 'A' || c == 'e' || c == 'E' || c == 'i' || 
    c == 'I' || c == 'o' || c == 'O' || c == 'u' || c == 'U' ) ; 
}