C isspace() function

C isspace(int ch)

The isspace() function is used to check whether a character is a space character or not. The function is defined in the ctype.h header file.


int isspace(int argument);

ispunct() Parameters:

Name Description Required /Optional
ch ch is a character of class upper in the current locale. Required

Return value from isupper()

  • The isspace() function return non-zero if ch is a white-space character; otherwise, they shall return 0.

Example: Check white-space character

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

int main()
    char c;
    int result;

    printf("Enter a character: ");
    scanf("%c", &c);
    result = isspace(c);

    if (result == 0)
        printf("Not a white-space character.");
        printf("White-space character.");

    return 0;


Input a character: A
The said character is not a white-space character.
Input a character:
The said character is White-space character.

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C Programming: Tips of the Day

Reading a string with scanf :

An array "decays" into a pointer to its first element, so scanf("%s", string) is equivalent to scanf("%s", &string[0]). On the other hand, scanf("%s", &string) passes a pointer-to-char[256], but it points to the same place.

Then scanf, when processing the tail of its argument list, will try to pull out a char *. That's the Right Thing when you've passed in string or &string[0], but when you've passed in &string you're depending on something that the language standard doesn't guarantee, namely that the pointers &string and &string[0] -- pointers to objects of different types and sizes that start at the same place -- are represented the same way.

Ref : https://bit.ly/3pdEk6f