C++ Program to Convert String to Uppercase

Write a C++ Program to Convert String to Uppercase with an example. In this C++ program, we used for loop (for (int i = 0; i < lwTxt.length(); i++)) to traverse lwTxt string characters. Within that, we used the toupper function (lwTxt[i] = toupper(lwTxt[i])) to convert lowercase string to uppercase.

#include<iostream>
#include<string>
using namespace std;

int main()
{
	string lwTxt;
	
	cout << "\nPlease Enter the String to Convert into Uppercase  =  ";
	getline(cin, lwTxt);
	
	for (int i = 0; i < lwTxt.length(); i++)
  	{
  		lwTxt[i] = toupper(lwTxt[i]);
  	}
  	
	cout<< "\nThe Given String in Uppercase = " << lwTxt;
		
 	return 0;
}

 The C++ algorithm file has a transform function that converts the lowercase string to uppercase.

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

int main()
{
	string lwTxt;
	
	cout << "\nPlease Enter the String to Convert into Uppercase  =  ";
	getline(cin, lwTxt);
	
	std:: transform(lwTxt.begin(), lwTxt.end(), lwTxt.begin(), ::toupper);
	
	cout<< "\nThe Given String in Uppercase = " << lwTxt;
		
 	return 0;
}

Output

Please Enter the String to Convert into Uppercase  =  hello world

The Given String in Uppercase = HELLO WORLD

C++ Example to Convert String to Uppercase using a While loop

#include<iostream>
#include<string>
using namespace std;

int main()
{
	string lwTxt;
	int i = 0; 
	
	cout << "\nPlease Enter the String to Convert into Uppercase  =  ";
	getline(cin, lwTxt);
	
	while(i < lwTxt.length())
  	{
  		if(islower(lwTxt[i]))
  		{
  			lwTxt[i] = toupper(lwTxt[i]);
		}
		i++;
  	}
  	
	cout<< "\nThe Given String in Uppercase = " << lwTxt;
		
 	return 0;
}

Output

Please Enter the String to Convert into Uppercase  =  c++ Programs

The Given String in Uppercase = C++ PROGRAMS

In this C++ code to Convert String to Uppercase, instead of converting all the characters, we used the if statement (if(lwTxt[i] >= ‘a’ && lwTxt[i] <= ‘z’)) to check whether the character is lowercase. If true, we are subtracting 32 from the ASCII Value to get the uppercase character.

#include<iostream>
#include<string>
using namespace std;

int main()
{
	string lwTxt;
	
	cout << "\nPlease Enter the String to Convert into Uppercase  =  ";
	getline(cin, lwTxt);
	
	for (int i = 0; i < lwTxt.length(); i++)
  	{
  		if(lwTxt[i] >= 'a' && lwTxt[i] <= 'z')
  		{
  			lwTxt[i] = lwTxt[i] - 32;
		}
  	}
  	
	cout<< "\nThe Given String in Uppercase = " << lwTxt;
		
 	return 0;
}

Output

Please Enter the String to Convert into Uppercase  =  tutorial gateway

The Given String in Uppercase = TUTORIAL GATEWAY

In this C++ Convert String to Uppercase example, we used the If statement. Within the If statement (if(lwTxt[i] >= 97 && lwTxt[i] <= 122 )), we used ASCII values to identify the lowercase characters in a string.

#include<iostream>
#include<string>
using namespace std;

int main()
{
	string lwTxt;
	
	cout << "\nPlease Enter the String to Convert into Uppercase  =  ";
	getline(cin, lwTxt);
	
	for (int i = 0; i < lwTxt.length(); i++)
  	{
  		if(lwTxt[i] >= 97 && lwTxt[i] <= 122 )
  		{
  			lwTxt[i] = lwTxt[i] - 32;
		}
  	}
  	
	cout<< "\nThe Given String in Uppercase = " << lwTxt;
		
 	return 0;
}

Output

Please Enter the String to Convert into Uppercase  =  tutorialgateway

The Given String in Uppercase = TUTORIALGATEWAY

C++ Program to Convert String to Uppercase using Functions

#include<iostream>
#include<string>
using namespace std;

string stringUpper(string lwTxt)
{
	for (int i = 0; i < lwTxt.length(); i++)
  	{
  		if(lwTxt[i] >= 'a' && lwTxt[i] <= 'z')
  		{
  			lwTxt[i] = lwTxt[i] - 32;
		}
  	}
  	return lwTxt;
}
int main()
{
	string lwTxt;
	
	cout << "\nPlease Enter the String to Convert into Uppercase  =  ";
	getline(cin, lwTxt);
	
	string up = stringUpper(lwTxt);
  	
	cout<< "\nThe Given String in Uppercase = " << up;
		
 	return 0;
}

Output

Please Enter the String to Convert into Uppercase  =  hello 2020 world!

The Given String in Uppercase = HELLO 2020 WORLD!