Date: Thursday, 13 November 1986
From: seismo!ubc-vision!alberta!myrias!cg (Chris Gray)
To: Keith Petersen, W8SDZ
Re: DRACO CP/M-80 software suite uploaded
The following files are the complete DRACO software suite:
--> FILE: DRACO-1 .ARC CRC = 0B B6
--> FILE: DRACO-2 .ARC CRC = B8 3C
--> FILE: DRACO-3 .ARC CRC = 6A 97
DRACO-1.ARC - documentation - writeups on the language, tools, programs,
etc. Also contains lots of sample Draco sources.
DRACO-2.ARC - compiler - contains the compiler, linker, assembler,
disassembler, librarian, cross-referencer, libraries and include files.
DRACO-3.ARC - programs - contains programs which must be configured using
the CONFIG program: several games and the editor.
What is Draco, Why Did I Write It and Why Is It Like It Is?
I usually describe Draco (pronounced Dray-ko) as a "systems
programming language". That means that it is a language which is
suitable for what I think of as systems programming - writing
operating systems, compilers, editors, databases, etc. This doesn't
mean that it isn't suitable for other applications such as writing
games, graphics programs, numerical programs, etc. It does mean that
the language has all of the facilities needed for the former type of
programming, such as bit operators, pointer manipulation, support for
complex data structures, etc.
What is different about Draco? I won't try to compare it with
every other programming language in the world; instead I'll stick to
two of the most popular ones for micros nowadays - C and Pascal. Draco
has all of the facilities of C, except for bitfields and the macro
preprocessor. Unlike C, and like Pascal, it is a strongly typed
language. This means that it won't let you assign an integer to a
pointer (unless you really insist). It is also not an expression
language like C, thus it makes a quite strict distinction between
statements like "a := 27" and expressions like "a + 27". Pascal is
strongly typed, but lacks many of C's facilities - pointer
manipulation, bit manipulation, standard separate compilation,
conditional compilation, etc. I like to think that Draco combines the
best features of both languages.
Visually, Draco doesn't really resemble either language closely,
but is a little closer to Pascal than C. It uses ':=' for assignment
and '=' for comparison, like Pascal and unlike C. It's structure and
union declarations are like those of C, however. As a simple
comparison, here follows the same program, written in Pascal, C, and
Draco:
Pascal:
PROGRAM test(INPUT, OUTPUT);
VAR
i, j : INTEGER;
BEGIN
FOR i := 0 TO 10 DO BEGIN
FOR j := 0 TO i DO
WRITE(j : 2, ' ');
WRITELN
END;
WRITELN("All done.")
END.
C:
#include <stdio.h>
main(argc, argv)
int argc;
char *argv[];
{
int i, j;
for (i = 0; i <= 10; ++i) {
for (j = 0; j <= i; ++j)
printf("%2d ", j);
printf("\n");
}
printf("All done.\n");
}
Draco:
proc main()void:
int i, j;
for i from 0 upto 10 do
for j from 0 upto i do
write(j : 2, ' ');
od;
writeln();
od;
writeln("All done.");
corp;
First, it's clear that the C program has lots of brackets, while
the Pascal and Draco programs have lots of keywords. A significant
difference, not very clear in this small example, is that Draco uses
different keywords for each job, rather than relying on a single
construct (the BEGIN - END or '{' - '}' block). I greatly prefer
keywords, finding them easier on the eye. I also prefer languages in
which the use of case (UPPER v.s. lower) is available for my own
purposes, rather than having them equivalent as in most Pascals. Also,
note that the Draco program uses 'upto' in the 'for' loops - this
tells the compiler that the loop will be counting upwards; 'downto' is
used for downward counting loops. C doesn't really have a semantically
different 'for' loop - it's is just a kind of shorthand for a 'while'
loop.
Some of the inadequacies of Pascal from my point of view are as follows:
- no standard separate compilation
- no conditional compilation
- no general string mechanism
- no pointer manipulation
- no bit manipulation
- I HATE BEGIN and END!
- no signed/unsigned types
- limitations on function and argument types
- procedure calls don't use '()' - they look like variables
- no typed, named, constants
- no available, decent implementations (fast compilation, good code,
nice libraries, good error reporting)
- I/O semantics that are poor for interactive programs
- no file inclusion or module specification facility
Some of the inadequacies of C from my point of view:
- too many bloody brackets!
- horrible declaration syntax (just what is "char *(*p[])()"?)
- error prone conventions (how many times have YOU written '=' when
you meant '=='?)
- non-portable I/O (if you don't believe this, take a look at the
open calls on CP/M or MS-DOS versions of C, where you get to tell
it what it's supposed to do with '\n')
- potential for extremely unreadable code (misuse of macros, etc.)
- slow compilers (as I've heard it, the reason that the original UNIX C
compiler for the PDP-11 generated assembler source was so that the
compiler writers didn't have to worry about long/short branch
optimization, since that was done by the assembler. Producing
assembler source is just plain slow. Those who argue that they want
to hand edit it to improve it are crazy!)
- lack of much type checking (I prefer compilers that tell me about my
dumb mistakes. This a lot better in the ANSI draft version.)
- inefficient standard setup - passing everything as 16 bits on an 8
bit CPU isn't so hot
- stupid linkers - why add all that code I'm never calling?
- no built-in I/O - this makes even the simplest programs large
- no typed, named constants
All of these issues have been addressed in the Draco language and
tools. Just as important to me is the quality of the tools (compiler,
linker, etc.) The Draco compiler goes from source code to
relocatable, optimized machine code at a rate of about 2000 lines per
minute on a 5 MHz 8085. Working from one 8" floppy disk, the entire
compiler (about 10,000 lines) can be rebuilt in under 10 minutes. No
other compiler I've heard of for CP/M can do this (at least not and
produce good code). The linker will link small programs in one quick
pass, and won't load any code that isn't referenced by the program. A
simple "hello there world" program is under 1000 bytes.
Another reason that these programs exist is that I LIKE writing
compilers and stuff. I'm up to about seven compilers now, the latest
of which is a C compiler that should meet the ANSI draft standard
(it's a huge monster written in C, but at least I was paid to write
it!)
So I've written my very own personal compiler, that does things
just the way I want; why should anyone else want to use it? Put
simply, the Draco package (which includes the various libraries I've
built up) is possibly the most effective way to produce compact,
efficient code for CP/M systems. In the past couple of years, asside
from fine tuning the compiler, I've written somewhere around 20,000
lines of Draco code, including the screen editor I'm typing this into,
a complex graphic role-playing game, several CRT-oriented games for
CP/M, ranging from the trivial to the quite complex, a database
package, a text processor (with a friend), a modem program, etc. If
you want to program a CP/M system, whether for fun, profit or
whatever, and are willing to learn another language, then I feel that
Draco is a valid choice.
To be fair, I will end this intro with a list of things that I
find are lacking in the this version of Draco:
- essentially non-existant floating point support
- no proper modules (although Draco goes about half way to providing a
usable kind of module)
- no bit oriented type (I haven't yet fully convinced myself that this
is needed)
- error handling is considerably better than most C compilers I've
heard of, but it could still use some improvement
- object code can ALWAYS use improvement, but the improvements that are
left would either be difficult or of little actual benefit and
would probably make the compiler too big to fit on standard CP/M
systems
and, of course
- Draco is supported only by me, and available only on the systems that
I choose to put it on (currently CP/M-80 and Commodore Amiga,
although the Amiga version hasn't been widely released yet)
About the Draco Disks
There are 3 disks in this set:
1 - documentation - writeups on the language, tools, programs, etc.
Also contains lots of sample Draco sources.
2 - compiler - contains the compiler, linker, assembler, disassembler,
librarian, cross-referencer, libraries and include files
3 - programs - contains programs which must be configured using the CONFIG
program: several games and the editor
All material on these disks are supplied "as is" with no warrantees or
guarantees of any kind. The tools, especially the compiler and linker, have
been heavily used and should be fairly bug free. Some of the games have
known glitches.
All material on these disks is supplied as "copyrighted shareware". This
means that you can use the supplied material as you see fit, and you can
give away copies of the disks to anyone, so long as this file, named
"README.TXT" is included on each disk. The author retains all other rights
to the software.
This software was originally intended as commercial software, and some of
the writeups reflect this orientation. Due to the lack of a viable market
for CP/M-80, character based software, this software is now being
distributed as "shareware", in which user's are requested to send a suitable
donation to the author if they feel the software merits it. Such
contributions can be thought of as encouragement to the author to create
and release more software and more versions of the current software.
Currently under way is a conversion of the compiler to generate MC68000
code. The immediate target machine is the Commodore Amiga. Soon to follow
that is a comprehensive graphics adventure system originally written for
CP/M-80 using the Compupro "Spectrum" graphics board.
Contributions can be sent to:
Chris Gray
Apt. #1612, 8515 112 Street,
Edmonton, Alberta, CANADA. T6G 1K7