Michael Schnell wrote:
On 11/16/2010 02:52 PM, Paul Breneman wrote:
I try hard to write Pascal programs without using pointers and without
allocating or deallocating memory.
OOpps. How is this possible :) ? But in what way does this help on that
issue ? I do see that memory allocation/deallocation is a source to very
hard to find bugs, but avoiding it makes may things close to impossible.
I don't doubt that there are certain domains where application-level
memory allocation/deallocation is very necessary. But for the type of
programs I usually write it isn't. I've written a lot of machine
control projects with TurboPascal starting in 1985. The only strings
(short) at that time were still long enough for the serial data buffers
I needed.
In 1985 I started working on an existing real-time video editing program
written in PDP-11 assembler. In the early 90s I ported that to pure
TurboPascal (no assembler) with ~50,000 source lines. The only
interrupts were for the keyboard and also a video timing interrupt (50
or 60 Hz) and about one-third of the code lived in the timing interrupt
routine. One system had 24 RS-422 serial ports (38,400 baud) in an
inexpensive RadioShack Tandy 386 computer, which was the main computer
that controlled about $2 million of digital video editing equipment.
Quite a funny picture in a way (a peasant running a rich kingdom)...
Several fellows who developed such PC-based editors before me had to use
expensive and complex intelligent multi-port serial port cards but
thankfully I waited just long enough that the 16550 UART (with the 16
byte FIFO) had arrived on the scene so my system was much simpler. All
of the commands (during the real-time recording) were 16 bytes or less
so using 16550 UARTS it all worked without interrupts for the serial ports.
I just went back and searched the ~50,000 likes of source, and there is
not a single New/Dispose (nor Mark/Release) in all of my code. My
program never crashed (even at the beginning beta stage) and I never
used a debugger but rather a little logging when needed.
All video editing is now done with fast computers but here is a freeware
version of that program that can utilize 9 serial ports:
http://www.brenemanlabs.com/MachOne5.htm
http://www.brenemanlabs.com/Mach1I.htm
One of my favorite authors (Jack Crenshaw) likes TurboPascal a lot, and
(if I remember right) years ago he wrote something along the lines of:
When I compile a C program I'm surprised if it runs the first time, but
when I compile a TurboPascal program I'm surprised if it doesn't run the
first time.
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