Just what are Batch Files Anyway?

In their simplest form, batch files are just files that COMMAND.COM interprets as a sequence of commands, as if they had been entered from the command prompt. A trivial example is a batch file to invoke a program and then clear the screen when it finishes:

Another simple example creates a directory and changes to it:

However, that isn't really useful, since the program would be needed only once, and it is less effort to simply issue the commands from the prompt. Batch language has extension to the commands that can be issued from the prompt to allow replaceable parameters to be passed on the command line when the batch program is invoked. Adding a single replaceable parameter (command line arguments are referenced by '%' followed by a number) to the above makes it quite useful:

If this batch file were named ND.BAT, then the command

would create the subdirectory \TEST in the default directory and change to it automatically. The first example can also be improved by adding "%1" after the EDIT command, so that you can specify the file to be edited in the invocation command.

Even single line commands can benefit from being encapsulated in a batch file, especially where the command is lengthy and only one or two elements vary from use to use, as in this program (UNZIP.BAT) that I have used for years:

which never forgets to use the -d switch for PKUNZIP (to properly expand a ZIP file containing subdirectories). Another useful example is QBASRUN.BAT, which launches QBASIC and causes it to automatically execute the program passed as the command argument:

Obviously, there is more to batch files than indicated here, but this is pretty much the original idea behind them. There are many other features and enhancements, but these will be addressed in other essays.