out putting upper case letters

Can anyone help me figure out what im doing wrong? I want to input a string of characters, or better yet, multiple lines of strings, and out put them as capital letters. What i have so far will allow you to input a string but it only outputs the 1st letter.

Code:

#include <iostream>
#include <string>
using namespace std;
int main()
{
    int i;
    char a;
    string str;
    cout << "Enter a string of characters to convert to uppercase: ";
 
    for (i = 0; i < 100; i++)
    {
    cin >> str;
    cout << (char)(toupper(str.at(a)));
    }  


    return 0;    
}

First, 'a' is uninitialized, but you are using it as an index. My compiler warns me about this - if yours does not, adjust its warning settings until it does, then fix any and all warnings it gives you.

Second, you probably want 'str.at(i)' and to only run while 'i < str.length()'.

Which compiler do you use? When i make those changes ^ it doesnt allow me to input anything.

HAHAHA just kidding. I got it.