Count the number of letters, digits and special characters in C program

Question

So here is my code and I am struggling with the ispunct() ; it starts counting in 8 and in isalpha() it starts counting in 1 so I print it noAlpha-1, but in ispunct() it is awkward to put noSpecial-8 to become accurate. I don't have any issues in digits. What might be the problem here?

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

int main(){
    
    char string[100];
    int i, noAlpha, noDigit, noSpecial;
        
       printf("Input the string : ");
       gets(string);    

 
        noAlpha=0;
        noDigit=0;
        noSpecial=0;
        
        for(i=0;i<100;i++) {
     
        if(isalpha(string[i]))
        noAlpha++;
    
        
        if(isdigit(string[i]))
        noDigit++;
        
        if(ispunct(string[i]))
        noSpecial++;
    }
        
        printf("Number of Alphabets in the string is %d\n", noAlpha-1);
        printf("Number of Digits in the string is %d\n", noDigit);
        printf("Number of Special characters in the string is %d\n", noSpecial);
}

Answer 1

The function gets is unsafe and is not supported by the C Standard.

Either use fgets like

fgets( string, sizeof( string ), stdin );

or scanf like

scanf( "%99[^\n]", string );

The entered string can be less than the size of the array string. So this loop

for(i=0;i<100;i++) 

invokes undefined behavior.

Instead you should use

for(i=0; string[i] != '\0'; i++) 

It is better to rewrite the if statements like if-else statements

    unsigned char c = string[i];

    if( isalpha( c ) )
    {
        noAlpha++;
    }
    else if( isdigit( c ) )
    {
        noDigit++;
    }
    else if( ispunct( c ) )
    {
        noSpecial++;
    }

So the output will look like

    printf("Number of Alphabets in the string is %d\n", noAlpha);
    printf("Number of Digits in the string is %d\n", noDigit);
    printf("Number of Special characters in the string is %d\n", noSpecial);

Answer 2

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

int main(){
    
    char string[100];
    int i, noAlpha, noDigit, noSpecial;
        
       printf("Input the string : ");
       scanf( "%99[^\n]", string );    

 
        noAlpha=0;
        noDigit=0;
        noSpecial=0;
        
        for(i=0; string[i] != '\0'; i++) {
     
        unsigned char c = string[i];

        if( isalpha( c ) )
        {
        noAlpha++;
        }
        else if( isdigit( c ) )
        {
        noDigit++;
        }
        else if( ispunct( c ) )
        {
        noSpecial++;
        }
        }
        
        printf("Number of Alphabets in the string is %d\n", noAlpha-1);
        printf("Number of Digits in the string is %d\n", noDigit);
        printf("Number of Special characters in the string is %d\n",noSpecial);
}