SOD 32 is an imaginary 32 bit processor that is optimized for the execution of Forth. This package contains a software simulator in C plus a Forth that can be run on the simulator. The speed of that forth is competitive with some of the available Forth interpreters in C, but that was not the main goal when I developed it. After all I wrote it just for the hack value. It is released under the GNU General Public License version 2.
This Forth is almost as small as it can be. It is closely modeled after ANSI Forth, but it is not a complete implementation. It is just big enough that it can recompile itself with its own cross compiler.
Because the Forth system and its cross compiler are small and well commented they have a certain instructional value as well.
A glossary generator is provided and it produces a glossary of all Forth words in the file forth.glo.
You can probably still find the draft proposed ANS Forth standard on ftp.uu.net:/vendor/minerva/x3j14/dpans6ps.zip
Technical documentation about the SOD 32 processor, its simulator and its Forth can be found in the file sod32.doc and in the various source files.
After you unpack the shar archives you will have the following files:
- Makefile
- README.md
- sod32.h
- main.c
- special.c
- engine.c
- engine.S
- kernel.img
- sod32.txt
- extend.4th
- cross.4th
- kernel.4th
- sod32.4th
- doglos.4th
- glosgen.4th
If your system is big-endian (680x0), then uncomment the -DBIG_ENDIAN flag in the Makefile. Check that the UNS8 INT32 and UNS32 types in sod32.h are defined right for your system as unsigned 8 bit character, signed 32 bit integer and unsigned 32 bit integer. Adjust MEMSIZE to a reasonable value. Set the CC variable in the Makefile to the C compiler you will use. Now type
touch kernel.img
make
If everything goes well, you have an executable sod32, the file forth.img and the glossary forth.glo.
Start Forth with
./sod32 forth.img
Now you can type Forth words.
134 2 * .
will show
268 OK
WORDS will show all available forth words. You can load other files with
S" name" INCLUDED
This way you can load the cross compiler cross.4th, which will recompile kernel.img You can also load the glossary generator or the sod32 simulator.
S" sod32.4th" INCLUDED SOD32 forth.img
will bring up Forth in a simulator under Forth. It will be slow and you cannot do file operations, but nearly everything else.
You leave SOD 32 Forth by typing
BYE
The SOD 32 simulator is written in ANSI C. It should run on any platform that provides:
- 8 bit bytes.
- An unsigned 32 bit integer type.
- Two's complement integer representation.
It should run just fine with 32-bit C compilers on the 386, the 68000 and the vast majority of Unix work stations. There is even a chance that it runs with 16-bit DOS C compilers if you restrict the memory size to 64kB and you use unsigned long for UNS32. The simulator uses no operating system specific functions and therefore it is more portable than, say PFE.
It mimics a big-endian machine regardless of the endianness of the system you run it on.
A binary file kernel.img is included in the package. This is considered a bad thing on comp.sources.misc, but the inclusion is in my opinion justified for the following reasons.
- the file is machine independent. The same file can be used on every machine that can run the SOD 32 simulator.
- the file in necessary to run SOD 32 Forth. The source for the file is included in the form of cross.4th and kernel.4th, but you need to be able to run Forth in order to compile kernel.img from it. If I did not include it, you would first need to find a suitable other Forth.
- As this Forth is more easily portable than most other Forths, having to use another Forth system first before you can use this package, would seriously hinder its usefulness.