A very simple example for students ...

capslock.cpp

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    bool caps = false;
    cin >> n;

    string result;
    while(n--)
    {
        string str;
        char ch;
        cin >> str;

        if (str == "CAPS") {
            caps = !caps;
            continue;
        }

        ch = str[0];
        if (caps) {
            result += ch <= 'Z' ? tolower(ch) : toupper(ch);
            continue;
        }

        result += ch;
    }

    cout << result << endl;
    return 0;
}