C ctype.h isgraph() Function

isgraph() Function

The isgraph() function in C checks whether a character has a graphical representation, meaning it verifies if the character is printable and not a space. This function is useful when you need to filter out non-visible characters from user input or text processing operations.

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Syntax of isgraph()

int isgraph(int c);

Parameters

Parameter	Description
c	An integer representing the character to be checked, typically cast from a char or EOF.

Note that the isgraph() function considers all printable characters except for the space character (‘ ‘).

Return Value

The function returns a nonzero value (true) if the character has a graphical representation, and zero (false) if it does not.

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Examples for isgraph()

Example 1: Checking a Printable Character

This example demonstrates how to use isgraph() to verify if a given character is graphical.

Program

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

int main() {
    int ch = '!';
    
    if (isgraph(ch)) {
        printf("The character %c has a graphical representation.\n", ch);
    } else {
        printf("The character %c does not have a graphical representation.\n", ch);
    }
    
    return 0;
}

Explanation:

1. A character variable ch is initialized with the value '!'.
2. The isgraph() function checks whether '!' has a graphical representation.
3. Since '!' is a printable character and not a space, the function returns true.
4. The program prints a message confirming that the character has a graphical representation.

Program Output:

The character ! has a graphical representation.

Example 2: Evaluating a Space Character

This example illustrates how isgraph() returns false for the space character, which does not have a graphical representation.

Program

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

int main() {
    int ch = ' ';
    
    if (isgraph(ch)) {
        printf("The character (space) has a graphical representation.\n");
    } else {
        printf("The character (space) does not have a graphical representation.\n");
    }
    
    return 0;
}

Explanation:

1. The character ' ' (space) is assigned to the variable ch.
2. The isgraph() function checks if the space character has a graphical representation.
3. Since space is excluded from graphical characters, the function returns false.
4. A message is printed indicating that the space character does not have a graphical representation.

Program Output:

The character (space) does not have a graphical representation.

Example 3: Processing a String of Characters

This example demonstrates how to iterate over a string and use isgraph() to determine which characters are graphical.

Program

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

int main() {
    char str[] = "Hi there!";
    int i = 0;
    
    while (str[i] != '\0') {
        if (isgraph(str[i])) {
            printf("Character '%c' is graphical.\n", str[i]);
        } else {
            printf("Character '%c' is not graphical.\n", str[i]);
        }
        i++;
    }
    
    return 0;
}

Explanation:

1. A string "Hi there!" is defined.
2. The program loops through each character of the string.
3. For every character, isgraph() checks if it is a printable graphical character (excluding spaces).
4. Appropriate messages are printed for each character based on whether they are graphical or not.

Program Output:

Character 'H' is graphical.
Character 'i' is graphical.
Character ' ' is not graphical.
Character 't' is graphical.
Character 'h' is graphical.
Character 'e' is graphical.
Character 'r' is graphical.
Character 'e' is graphical.
Character '!' is graphical.