5.5. What is CSDPMI*B.ZIP and why do I need it?

If you use MS-DOS outside of Windows and try to use GNU sed v1.18 or 3.02, you may encounter the following error message:

       no DPMI - Get csdpmi*b.zip

"DPMI" stands for DOS Protected Mode Interface; it's basically a means of running DOS in Protected Mode (as opposed to Real Mode), which allows programs to share resources in extended memory without conflicting with one another. Running HIMEM.SYS and EMM386.EXE is not enough. The "CSDPMI*B.ZIP" refers to files written by Charles Sandmann to provide DPMI services for 32-bit computers (i.e., 386SX, 386DX, 486SX, etc.). Download the binary file (the source code is also available):

       https://www.delorie.com/djgpp/dl/ofc/simtel/v2misc/csdpmi5b.zip  # binaries
       https://www.delorie.com/djgpp/dl/ofc/simtel/v2misc/csdpmi5s.zip  # source
       ftp://ftp.cdrom.com/pub/simtelnet/gnu/djgpp/v2misc/csdpmi5b.zip # binaries
       ftp://ftp.cdrom.com/pub/simtelnet/gnu/djgpp/v2misc/csdpmi5s.zip # source

and extract CWSDPMI.EXE, CWSDPR0.EXE and CWSPARAM.EXE from the ZIP file. Put all 3 CWS*.EXE files in the same directory as GSED.EXE and you're all set. There are DOC files enclosed, but they're nearly incomprehensible for the average computer user. (Another case of user-vicious documentation.)

If you're running Windows and you normally use a DOS session to run GNU sed (i.e., you get to a DOS prompt with a resizable window or you press Alt-Enter to switch to full-screen mode), you don't need the CWS*.EXE files at all, since Windows uses DPMI already.