Ok, here's some links you should check out and below, a simple example.
Try it out, make changes, read the documentation and enjoy the endless possibilities it provides.
rand() function
http://www.cplusplus.com/reference/clibrary/cstdlib/rand/
srand() function (generates a random seed)
http://www.cplusplus.com/reference/clibrary/cstdlib/srand/
Time library from c where we can get the time_t time ( time_t * timer ); function
http://www.cplusplus.com/reference/clibrary/ctime/
ASCII codes:
http://es.wikipedia.org/wiki/ASCII
#include <iostream>
//ctime is used to set the random seed.
#include <ctime>
int main(int argc, char** argv)
{
using namespace std;
/*Initializes de seed to use the current time
so that the numbers are different each run
of the application*/
srand((unsigned)time(NULL));
/*Check the ASCII code values.
Lowercase goes from a = 97-> z=122
Uppercase goes from A = 65 -> Z=90 */
//rand() returns a number between 0 and RANDMAX
//arbitrarily, I decided to show 40 random letters
for(int iii=0;iii<40;iii++)
{
char letter = rand()%25 + 65;
cout<<letter<<" ";
}
/*
Exercise 1: change 65 to 'A'
Exercise 2: change 65 to 'a'
3: Use a number as a seed (instead of the time(NULL) function)
and you'll always get the same succession of random numbers"
4: Test and research
*/
}
Good luck and remember, be specific when you ask for help and show what you have done so far. http://www.catb.org/esr/faqs/smart-questions.html