Problems you may encounter under DOS

No space in environment.
An error message like this can occur if you call SET_PP.BAT in AUTOEXEC.BAT.
To solve this problem, you must extend your environment memory. To do this, search a line in CONFIG.SYS like

SHELL=C:\DOS\COMMAND.COM

and change it to the following:

SHELL=C:\DOS\COMMAND.COM /E:1024

You may just need to specify a higher value, if this parameter is already set.

Coprocessor missing
If the compiler writes a message that there is no coprocessor, install the coprocessor emulation.

Not enough DPMI memory
If you want to use the compiler with DPMI you must have at least 7-8 MB free DPMI memory, but 16 Mb is a more realistic amount.