My teen years: Porting Small-C to transputer and developing my operating system

C is very hard

The Small-C compiler

Transputer Summer

    /* Add the primary and secondary registers */
/*      (results in primary) */
zadd()
{       ol("add");
}
/* Subtract the primary register from the secondary */
/*      (results in primary) */
zsub()
{
 ol("rev");
 ol("sub");
}
/* Multiply the primary and secondary registers */
/*      (results in primary */
mult()
{       ol("mul");
}
/* Divide the secondary register by the primary */
/*      (quotient in primary, remainder in secondary) */
div()
{       ol("rev");
 ol("div");
}

A Dutch Operating System

Bootstrapping an operating system

Archeology on your own disk

1. The transputer emulator will be running MAESTRO.CMG (MAnejo de Entrada y Salida de Transputer por Oscar, or simply input/output handling for transputer by Oscar)
2. Setting up a 1.44 mb. disk image file: dd if=/dev/zero of=disk.img bs=1 count=1474560
3. Copy ARRANQUE.CMG (the boot sector) into the first 512 bytes of the disk image.
4. Build an initial FAT system in sector 2 with 160 bytes (one for each track, 80 tracks x 2 sides)
5. Build an initial directory image of ten sectors. Each entry measuring 32 bytes.
6. Add an initial entry SOM32.BIN that contains the basic operating system (SOM stands for Sistema Operativo Mexicano, or Mexican Operating System)
7. Add a second entry INTERFAZ.CMG containing the command-line processor. Problem here: The compiled version is missing from my archive.
8. Add the files EDITOR.CMG, ENSG10.CMG and TC2.CMG to complete the environment. Again I'm missing the EDITOR.CMG file but I've the C source code.
9. Add all the source files so these catn compile from the inside of the environment.

First three sectors of a working disk image for my transputer operating system. Notice my boot signature $12 $34 at offset 510.

1. I need to modify my transputer emulator to provide access to the disk image file.
2. I need to add several transputer instructions and some "paralellism" because it depends on the transputer switching processes.
3. I need to rebuild the missing INTERFAZ.CMG file to provide the command-line interface for the operating system.

1. Screen refresh: Takes a buffer, checks for changes, sends line updates to the host screen.
2. Middle-level BIOS: processes the BIOS calls, and sends back a slew of messages to the host system, probably because I wanted to isolate changes in the driver program.
3. Main execution: This boots the operating system and calls it.
4. Sleeper: A low level process that simply sleeps.

Iptr=800002f3 A=ffffffff B=ffffffff C=ffffffff Wptr=8001ddb0 ldlp 16
Iptr=800002f6 A=8001ddf0 B=ffffffff C=ffffffff Wptr=8001ddb0 ldc 510
Iptr=800002f7 A=000001fe B=8001ddf0 C=ffffffff Wptr=8001ddb0 bsub
Iptr=800002f8 A=8001dfee B=ffffffff C=ffffffff Wptr=8001ddb0 lb
Iptr=800002fa A=00000034 B=ffffffff C=ffffffff Wptr=8001ddb0 eqc 18
Iptr=800002fc A=00000000 B=ffffffff C=ffffffff Wptr=8001ddb0 cj 22

    I?serte u? disc? c?? siste?a ?perativ?? y pu?se u?a tec?a???

    Inserte un disco con sistema operativo, y pulse una tecla...  

The big surprise

    ./tem -cc os/tc2.cmg
    ./tasm os/tc2.len os/cc.cmg os/stdio3.len

1. Create the service handler to interface with the host machine (MAESTRO.LEN)
2. Create the boot sector in transputer assembler code (ARRANQUE.LEN)
3. Compile the C compiler using Turbo-C on MS-DOS.
4. Compile itself in MS-DOS and assemble the generated file (TC.CMG) with the STDIO.LEN library.
5. Create a driver program in the host Z280 machine to handle C files for the transputer board.
6. Enhance the C compiler to use tree expression generator (TC2.CMG), and assemble it with STDIO2.LEN.
7. Compile SOM32.c and assemble with MENSAJES.LEN. Use this as SOM32.BIN inside the OS.
8. Compile Interfaz.c and assemble with STDIO3.LEN. Use this as INTERFAZ.CMG inside the OS.
9. Compile Editor.c and assemble with STDIO3.LEN. Use this as EDITOR.CMG inside the OS.
10. Compile TC2.c and assemble with STDIO3.LEN. Use this as CC.CMG inside the OS.
11. Compile ENSG10.c and assemble with STDIO3.LEN. Use this as ENSG10.CMG inside the OS.
12. Now you can do development inside the transputer OS.

    Sistema Operativo Multitarea de 32 bits. v1.00                      
    >>>>> (c) Copyright 1995 Oscar Toledo G. <<<<<
    
    A>                                                                          

#define write_memory_32(addr, word) memory[(addr) & MEMORY_MASK] = (word) & 0xff; \
memory[((addr) + 1) & MEMORY_MASK] = ((word) >> 8) & 0xff; \
memory[((addr) + 2) & MEMORY_MASK] = ((word) >> 16) & 0xff; \
memory[((addr) + 3) & MEMORY_MASK] = ((word) >> 24) & 0xff;

    #define Enqueue(ProcPtr, Fptr, Bptr) \
        if (*(Fptr) == NotProcess_p) \
            *(Fptr) = ProcPtr;\
        else \
            write_memory_32(*(Bptr) - 8, ProcPtr);\
              \
        *(Bptr) = ProcPtr;

Sistema Operativo Multitarea de 32 bits. v1.00                                  
>>>>> (c) Copyright 1995 Oscar Toledo G. <<<<<                                  
                                                                                
A>dir                                                                           
                                                                                
SOM32   .BIN         4,143  23-ene-19<5 10:59:00                                
INTERFAZ.CMG         2,369  23-ene-19<5 10:59:00                                
CC      .CMG        16,952  23-ene-19<5 10:59:00                                
INTERFAZ.C           5,885  23-ene-19<5 10:59:00                                
EDITOR  .C          17,093  23-ene-19<5 10:59:00                                
ENSG10  .C          28,617  23-ene-19<5 10:59:00                                
EDITOR  .CMG         5,295  23-ene-19<5 10:59:00                                
ENSG10  .CMG        10,876  23-ene-19<5 10:59:00                                
                                                                                
            8 archivos.                                                         
    1,336,320 bytes libres.                                                     
                                                                                
A>                                                                              

Some polish required

Using the programs

./tem -os maestro.cmg disk.img    

Text editor running on transputer

Final thoughts

Related links

• The source code for my transputer operating system, command-line interpreter, text editor, C compiler, and assembler. https://github.com/nanochess/transputer
• Dr. Dobb's Programming Journal volume 5.
• The history of my Pascal compiler for transputer.
• Transputer resources.