It is a good approach and back say 20 years ago the favorite was to redo the du command and add a conversion to MB (now handled by the -h option for human in the du and ls command).
Cat is also a good example and not just to learn a programming language but the OS. Ask somebody to come up with 20 ways to display a file, you can do it with not just the cat command. Now I'm not saying there are twenty ways, but it is one area which some delving and approach will allow people to try and find them.
Examples are for me the best way to learn a programming language and again with the simple Unix commands you have a common base which people are more likely to ifnd an example. Can't recall but great site on the net which has "Hello World" in about every programming language around.
After a while, you will start to add option to your redeveloped commands, then add entirely new commands and from there you can think about writting your own shell. No graphics or the like to distract you too much. Graphics as a rule in programming languages I have found to be like learning an after thought and also you are more controlled in the mentality behind the API. So I do advise not even looking at graphics for a while until you have learned how to flex the language without the distractions graphics and the way they are handled add a overhead to your code. I'm sure somebody will list a programming language that is easier to do graphicly as apposed to text output, though its a safe rule. SO just because you have windows, don't mean you have to jump into GUI's from day one, if even at all.
I remember that hello world site, I think it fell off the internet but there are still many of those types of sites. One of my favs was the 99 bottles song in many languages. There are also larger projects like PLEAC and Rosetta code that are similar.
Earlier this year, I did 21 different implementations of a hex dump program in C (starting here: http://boston.conman.org/2012/01/09.1). I also included implementations in a few other languages just for comparison. Why? It was a neat break from the programming I do for work.
Cat is also a good example and not just to learn a programming language but the OS. Ask somebody to come up with 20 ways to display a file, you can do it with not just the cat command. Now I'm not saying there are twenty ways, but it is one area which some delving and approach will allow people to try and find them.
Examples are for me the best way to learn a programming language and again with the simple Unix commands you have a common base which people are more likely to ifnd an example. Can't recall but great site on the net which has "Hello World" in about every programming language around.
After a while, you will start to add option to your redeveloped commands, then add entirely new commands and from there you can think about writting your own shell. No graphics or the like to distract you too much. Graphics as a rule in programming languages I have found to be like learning an after thought and also you are more controlled in the mentality behind the API. So I do advise not even looking at graphics for a while until you have learned how to flex the language without the distractions graphics and the way they are handled add a overhead to your code. I'm sure somebody will list a programming language that is easier to do graphicly as apposed to text output, though its a safe rule. SO just because you have windows, don't mean you have to jump into GUI's from day one, if even at all.