There are tons of possiblities to have counters depending on how do you access it and where does it keep the score. In this exercise you are required to implement a number of different counters. A few ideas follow:

A command-line single-counter. Every time we run the program it will display an ever increasing number: 

$ counter
1
$ counter
2
$ counter
3

A command-line multi-counter: 

$ counter Foo
1
$ counter Foo
2
$ counter Bar
1
$ counter Foo
3
$ counter Foo
4
$ counter Bar
2

Front-ends:

  • Command line
  • Web browser
  • GUI (e.g. Python Tk)

You can find many solutions in the Counter Examples project.