Bronze Edition Guide - True BASIC

211
Making Your Own DO Programs
APPENDIX
E
You may have noticed the directory “TBDo”, which contains several so-called “DO programs.”
Actually, they are not regular programs, but are subroutines. They are
designed to operate on the text file in the current editing window, but can be made to do
just about anything.
You can make your own DO programs. Follow these simple steps:
1. Create a library file, carefully choosing its name.
2. On the first lines of the library file, enter
EXTERNAL
SUB xxxxx (current$(), options$)
3 Now write what you want to do, which may involve modifying the lines or the
current file.
4. At the end of the file, enter
END SUB
Note: the actual name of the subroutine is irrelevant! A DO program is always identified
by the name of the file containing it!
Now save this file in the directory TBDo. When True BASIC starts up, the name or your
new do program file will appear in the Run menu along with the names of all the other
do programs.
You can invoke a do program in two ways. You can select the menu item “Do ...” in the
“Run” menu, or you can type the command “do filename” on the command line. (Of
course, you’ll actually type the file name you have selected.)
If you use the menu selection method, you may have to navigate the file system to find
the directory TBDo. Then you’ll also be asked for the the command line parameters.
Whatever you enter will then be assigned to the second argument in the calling