function
<cctype>

isalpha

int isalpha ( int c );
Check if character is alphabetic
Checks whether c is an alphabetic letter.

Notice that what is considered a letter depends on the locale being used; In the default "C" locale, what constitutes a letter is only what returns true by either isupper or islower.

Using other locales, an alphabetic character is a character for which isupper or islower would return true, or another character explicitly considered alphabetic by the locale (in this case, the character cannot be iscntrl, isdigit, ispunct or isspace).

For a detailed chart on what the different ctype functions return for each character of the standard ANSII character set, see the reference for the <cctype> header.

In C++, a locale-specific template version of this function (isalpha) exists in header <locale>.

Parameters

c
Character to be checked, casted to an int, or EOF.

Return Value

A value different from zero (i.e., true) if indeed c is an alphabetic letter. Zero (i.e., false) otherwise.

Example

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/* isalpha example */
#include <stdio.h>
#include <ctype.h>
int main ()
{
  int i=0;
  char str[]="C++";
  while (str[i])
  {
    if (isalpha(str[i])) printf ("character %c is alphabetic\n",str[i]);
    else printf ("character %c is not alphabetic\n",str[i]);
    i++;
  }
  return 0;
}


Output:
character C is alphabetic
character + is not alphabetic
character + is not alphabetic

See also

isalnum
Check if character is alphanumeric (function )
isdigit
Check if character is decimal digit (function )