Contributor: SWAG SUPPORT TEAM
SECTION 7 - DOS Programming
This document contains information that is most often provided
to users of this section. There is a listing of common
Technical Information Documents that can be downloaded from the
libraries, and a listing of the five most frequently asked
questions and their answers.
TI1184 Overview of Borland Pascal 7.0 and Turbo Pascal 7.0
TI1722 Declaring an array on the heap
TI1760 Creating a temporary stack in real or protected mode
TI1171 Problem Report Form
TI1719 Booting Clean
LC2P01.FAQ Linking C to Pascal Frequently Asked Questions
EZDPMI.ZIP Unit encapsulating common DPMI requests for
protected mode programming
BIGSTU.PAS How to cope with memory allocations > 64K
PASALL.ZIP Collection of Technical Information Sheets from
1986 on
NEWRTM.ZIP Latest RMT.EXE and DPMI16BI.OVL
MOUSE.ZIP General purpose mouse unit for text/graphic modes
Q. "How do I link an object file that is a library of
functions created in C?"
A. Download the file "LC2P01.FAQ. The C run-time library is
needed by the object file. Since Pascal can't link the C
RTL as is, you will need the RTL source and will need to
modify it so that it can be linked by TP.
Q. "How do I get the ASCII key numbers for the Arrow keys?"
A. Below is a short program that reveals this information.
program DisplayAscii;
uses Crt;
var
ch:char;
begin
repeat { repeat until Ctrl-C }
ch := Readkey;
Write(Ord(CH):4);
until ch = ^C;
end.
The program can be terminated by pressing Ctrl-C. You'll
see that keypresses such as UpArrow actually generated two
bytes: a zero followed by the extended key code.
Q. "Why do I get runtime error 4 while using the following
line: reset(InFile)?"
A. The error message means that you have run out of file
handles. The FILES= statement in your CONFIG.SYS doesn't
change the fact that a process can, by default, open a
maximum of 20 files (and DOS grabs 5 of those). The
SetHandleCount() API function can be used to increase the
number of handles useable by your application.
Q. "I am using overlays with BP7 with Objects. If Overlay A
calls a procedure or function in Overlay B, does Overlay A
stay in memory while Overlay B runs? Or does Overlay B
wipe out Overlay A, and when Overlay B finishes, it reloads
Overlay A?"
A. It depends on the size of the overlays and the size of the
overlay buffer you set up. In general you can think of the
overlay buffer as a pool of memory where overlaid units can
be stored. Every time you call a routine in an overlaid
unit, that overlay is loaded into the buffer. If the
buffer is already full, then the oldest unit in the buffer
is discarded to make room for the new one. If you've got a
small overlay buffer and large overlaid units, they may
well kick each other out as they load. If you've got a
large overlay buffer the program may well keep everything
in memory the entire time.
Q. "I am getting DosError = 8 when using EXEC() to execute a
program from within my program. How do I correct this?"
A. DosError = 8 means that there is not enough memory
available to run the program being EXEC'ed. Normally your
program grabs all available memory and doesn't leave any
for the program being EXEC'ed. Be sure to use the $M
directive which minimizes the memory required by your
program.
Q. "I am getting DosError = 2 when using EXEC() to copy a
file from one directory to another. The file does exist
and the command line is correct. What is the problem?"
A. You might have assumed that because COMMAND.COM is on your
path, EXEC will find it. Nope. EXEC needs the full path
name. You can use GetEnv('COMSPEC') to get the value of
the environment variable COMSPEC which should be the full
path.