[RC5] Re:

Joe Zbiciak j-zbiciak1 at ti.com
Thu Jan 29 00:29:40 EST 1998


'Sanford Olson' said previously:

| .EXE files also have a PSP, but it is not part of the program's CODE
| segment

This much I knew.  My memory ended there though.  :-)

|  (ok, .EXE's have multiple CODE segments and the PSP is in it's
| own).  Note, the command-tail doesn't include the program path and 
| filename:

Ok.  I've been programming in C under Unix too long.  I wasn't fully
grokking the idea of a command *tail* versus the whole command line,
which is what you nominally get in argv[].  (Granted, the DOS libc
runtimes set up the same (or similar) argv[] as Unix tends to, further
masking this concept of a command tail from me, the C programmer.)

Where is the full path to the EXE stored?  My foggy memory says that
around DOS 3.x they started hiding that just behind the environment
block, but I'm not certain.  I know the 8-character program name is
stored in part of the header just before the PSP as of DOS 4 or 5.  (Is
that header the MCB?  Whatever the name is for the chain of "memory
regions" in the "DOS memory arena" below 1MB....)

If I knew where my copy of "Undocumented DOS" was I'd go look all 
this up.  :-)

|    C:\RC5\RC5DESD.EXE param1 param2 -option1 -option2
|                       |
|                       + command-tail starts here


Ahh, ok.  It's been awhile.  :-)  So, then, the maximum command length
is technically "maximum pathname length" + "up to 127 characters of 
parameters."  

Thanks for the clarification.

--Joe

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