If you are still using MS-DOS applications, printing is one of the more problematic areas. Many modern inexpensive inkjet and laser printers don't even support output from DOS programs, as they don't have enough built-in smarts to form the character images by themselves. If you need laser or inkjet output from a DOS application, be sure that any new printer you buy uses a page-description language supported by your application, such as PostScript, Hewlett-Packard's PCL, or one of the Epson text formats.
Furthermore, most DOS applications can only print to LPT ports. If you want to use a printer that is on a USB port or is out there somewhere on a LAN, nothing will come out! To direct a DOS program's output to a USB or network printer, share the printer (even if it's attached to your own computer), issue the command
net use lpt2: \\computername\sharename
from the Command Prompt window, and then direct your DOS program to use LPT2. (You should select an LPT port number that does not have an associated physical LPT port in your computer.)
For more information about the net use command, p. 666.