I'm currently creating an experimental programming language for fun and educational purpose and in search for some tasks beyond the classical "Hello, World!"-program.

I've already come up with these ideas:

• Print out the program's input
• Calculator
• Generate Prime numbers, Fibonacci series

What other interesting programming problems do you have for me to test?

It would be good if they required the language to solve a broad spectrum of task, take prime numbers for example: You need variables, increment them, divide them, perform actions under certain conditions, etc.