iswlower() function in C++ STL

In C++ standard template library(STL), iswlower() function is used to check if the given wide character is in lowercase or not, if not then the function will return a zero value. The characters with ASCII value from 97 to 122 i.e. a-z are the lowercase alphabetic letters. Iswlower() function is present in cctype header file in C/C++.

Syntax of iswlower () is as follows

int iswlower (wint_t c)

Parameters − c is a wide character to be checked, casted to a wint_t, or WEOF where wint_t is an integral type.

Return Value − islower() function return non-zero value when the string is in lowercase else it will return a zero value.

For Example

Input − string[] = Test Me

Output − string has lowercase letters

Explanation − in the given string we checked whether it contains lowercase letters between a-z

Input − string[] = Test Me

Output − TEST ME

Explanation − In the given string we converted lowercase characters to the uppercase characters.

Approach used in the below program is as follows

  • Input the string in a wchar_str type variable

  • Apply the in-built iswlower() function of STL to check whether the string has lowercase letters or not

  • If the result is true then the function will return any non-zero value and if the result if false then the function will return zero value.

  • Display the final result


 Live Demo

#include <stdio.h>
#include <wctype.h>
int main (){
   int i=0;
   wchar_t str[] = L"Test String.\n";
   wchar_t c;
   while (str[i]){
      c = str[i];
      if (iswlower(c)) c=towupper(c);
         putwchar (c);
   return 0;


If we run the above code it will generate the following output −


Updated on: 27-Feb-2020


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