C <ctype.h> - isalpha() Function

The C <ctype.h> isalpha() function is used to check if the given character is an alphabetic letter. In the default "C" locale, an alphabetic letter is a letter for which either isupper or islower function returns true. Other locales may consider a different selection of characters as alphabetic letters.

Syntax

int isalpha ( int ch );               

Parameters

Return Value

Returns non-zero value (i.e, true) if ch is an alphabetic letter, else returns zero (i.e, false).

Example:

The example below shows the usage of isalpha() function.

#include <stdio.h>
#include <ctype.h>
 
int main (){
  char str[50] = "98Hi@@";

  //counting the numbers of 
  //alphabetic letters in str
  int i = 0, count = 0;
  while(str[i]) {
    if(isalpha(str[i]))
      count++;
    i++;
  }

  //displaying the output
  printf("%s contains %d alphabetic letters.", str, count);  
  return 0;
}

The output of the above code will be:

98Hi@@ contains 2 alphabetic letters.