Checking if string is only letters and spaces

Question

I wrote this simple code to check if a string is letters and spaces only

#include<stdio.h>
#include<conio.h>
#include<math.h>
#include<stdlib.h>
#include<string.h>
#define N 100

int checkString(char str1[]);

void main()
{
    char str1[N];

    scanf("%s", str1);

    printf("%d",checkString(str1));

    getch();
}

int checkString(char str1[])
{
    int i, x=0, p;
    p=strlen(str1);
    for (i = 0; i < p ; i++)
    {
        if ((str1[i] >= 'a' && str1[i] <= 'z') || (str1[i] >= 'A' && str1[i] <= 'Z') || (str1[i] == ' '))
        {
            continue;
        }
        else{ return 0; }
    }
    return 1;
}

This works fine when I type something like :

hello asds //returns 1

hello1010 sasd  // return 0

but if I type anything after space it returns 1, like this :

hello 1220  //returns 1

blabla 11sdws // returns 1

Can someone please tell me why?

Answer 1

The function can be written more simpler and correctly if to use standard C functions isalpha and isblank declared in header <ctype.h> For example

#include <ctype.h>

//...

int checkString( const char s[] )
{
    unsigned char c;

    while ( ( c = *s ) && ( isalpha( c ) || isblank( c ) ) ) ++s;

    return *s == '\0'; 
}

If you want to check whether a string contains white spaces then instead of function isblank you should use function isspace.

Take into account that it is not a good idea to use statement continue in such simple loops. It is better to rewrite the loop without the continue statement.

And instead of function scanf it is better to use function fgets if you want to enter a sentence The function allows to enter several words as one string until the Enter will be pressed.

For example

fgets( str1, sizeof( str1 ), stdin );

Take into account that the function includes the new line character. So after entering a string you should remove this character. For example

size_t n = strlen( str1 );
if ( n != 0 && str1[n-1] == '\n' ) str1[n-1] = '\0';

Answer 2

You forgot about the numbers

int checkString(char str1[]) {
    int i, x=0, p;
    p=strlen(str1);

    for (i = 0; i < p ; i++)
        if ((str1[i] >= 'a' && str1[i] <= 'z') || (str1[i] >= 'A' && str1[i] <= 'Z') || (str1[i] == ' ') || (str1[i] >= '0' && str1[i] <= '9')) {
            continue;
        } else return 0;

    return 1;
}

Or better

#include <ctype.h>
...

int checkString(char str1[]) {
    int i, x=0, p;
    p=strlen(str1);

    for (i = 0; i < p ; i++)
        if (isalnum(str1[i]) || (str1[i] == ' '))
            continue;
        else return 0;

    return 1;
}