Program to Convert string to lowercase or uppercase in C++

#include <iostream>
using namespace std;

void lower_string(string str)
{
	for(int i=0;str[i]!='\0';i++)
	{
		if (str[i] >= 'A' && str[i] <= 'Z')    //checking for uppercase characters
			str[i] = str[i] + 32;         //converting uppercase to lowercase
	}
	cout<<"\n The string in lower case: "<< str;
}

void upper_string(string str)
{
	for(int i=0;str[i]!='\0';i++)
	{
		if (str[i] >= 'a' && str[i] <= 'z')   //checking for lowercase characters
			str[i] = str[i] - 32;        //converting lowercase to uppercase
	}
	cout<<"\n The string in upper case: "<< str;
}

int main()
{
	string str;
    cout<<"Enter the string ";
    getline(cin,str);
    lower_string(str);       //function call to convert to lowercase
	upper_string(str);   //function call to convert to uppercase
	return 0;
}

Output:

Enter the string Hola Amigos!
The string in lower case: hola amigos!
The string in upper case: HOLA AMIGOS!