Introduction

I have used CodeBlocks compiler for debugging purpose. But you can use any C++ programming language compiler as per your availability.

#include <iostream>
#include <string.h>
using namespace std;
 
    void functionlower(char []);
 
    int main()
    {
       char string[100];
 
       cout<<"Enter a string to convert it into lower case: "<<endl;
       cin>>string;
 
       functionlower(string); // calling functionlower
 
       cout<<"Entered string in lower case is: "<<string;
 
       return 0;
    }
 
    void functionlower(char s[]) {
       int c = 0;
 
       while (s[c] != '\0') {
          if (s[c] >= 'A' && s[c] <= 'Z') {
             s[c] = s[c] + 32;
          }
          c++;
       }
    }

Result