api tutorial?

I am told the turtles come with built in shellapi or shell
Istart a Turtle an in my Turtle black window I type
> help shellapi
and get
> shell.exit()
> shell.dir()
I then type
> shell.dir()
No such program
> shell dir()
No such program
> shellapi.dir
No such program
> dir()
No such program

I use Google and find
http://computercraft.info/wiki/Tutorials
I try
http://computercraft.info/wiki/Guess_The_Number_%28tutorial%29
and type in their first command
> term.clear()
No such program

Can anyone tell the very frustrated person what I am failing to do?
I really need *exact* character-by-character instructions.

Thanks

You're on the right track, but you're using the LUA commands within the shell. You need to use them within a program
Type 'edit file' in the shell and then use the commands :)/>

Moved to Ask a Pro.

remiX, on 25 February 2013 - 06:31 AM said:

You're on the right track, but you're using the LUA commands within the shell. You need to use them within a program
Type 'edit file' in the shell and then use the commands :)/>

just to clarify, after you type the Lua script into "file", save it, then type "file" to run it

You can also run Lua commands directly from the "lua" program.
Example, where italics are what you typed:

CraftOS 1.5
> lua
(some text goes here that I never bother to read)
lua> term.clear()
screen clears
lua>