Filenames
While DOS 3.3 allows you to save a file with a file name that has a tilde for the first characater, ProDOS is much more strict:
--Only fifteen characters
--Only the letters A-Z, numbers 0-9, and a period
--Only a letter for the first character
--No control characters
Some acceptable filenames are:
PotatoSalad
SillyProgram
Biz.letter
Memo.1.April.84
Some unacceptable filenames are:
Potato Salad - can't have spaces
Ridiculousprogram - too long--greater than 15 characters
Emily'sPoem - apostrophes aren't legal characters
Memo: Bill - colons and spaces are illegal characters
If you forget these rules: for example, you leave a blank in the middle of a filename, your program beeps and the cursor won't budge until you type a character that is aceptable.
Directories
When a volume is first formatted, it gets a name and a directory. Anything you save on that volume is accessed through that directory. The directory is also a file, but it just tracks where other files on the disk are stored. You could say that a directory file is like an address book.
There comes a time -- especially with a mass storage disk -- when it's convienient to have a way of organizing your files so you find such things as financial forecasts without listing the contents of the entire disk.
Subdirectories allow you to group your files logically. A subdirectory is just like a directory except that it's subordinate to the directory.
In the directory for the disk, you can create a subdirectory with the name "Financial", and in this subdirectory you create the subdirectories with the names "Forecasts" or "Statements". This kind of arrangement is called a hierarchial file structure because files are organized into successive levels.