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The International Obfuscated C Code Contest

2006/toledo2 - Best of Show

An 8080 emulator

← 2006/toledo1 ↑ 2006 ↑ 2006/toledo3 → C code Makefile Inventory ✓

Author:

To build:

    make

There is alternate code that is based on the author’s notes for DOS/Windows. This cannot be tested by us, not even to compile, but it appears that it should be fine, after the proper header files were added.

Bugs and (Mis)features:

The current status of this entry is:

STATUS: INABIAF - please DO NOT fix

For more detailed information see 2006/toledo2 in bugs.html.

To use:

    ./toledo2

To end execution press ctrl-z. As mentioned in the author’s remarks and in the below section, it is supposed to crash on termination though some noted this does not seem to happen in macOS or linux in 2023.

Try:

    ./toledo2

and then type in the following:

    10 PRINT "HELLO WORLD!"
    LIST
    RUN

To end the program hit ctrl-z.

Alternate code:

This version, as noted above, should work for DOS/Windows. It uses non-standard functions in place of read(2) and write(2), and is based on the author’s remarks.

Alternate build:

    make alt

Alternate use:

The author noted that for PC/DOS you will have to add ANSI.SYS to your CONFIG.SYS but this is also something we can’t test.

Use toledeo2.alt as you would toledo2 above.

Judges’ remarks:

We’re impressed! Last year, it was a 6502 emulator; this year, it’s 8080! It requires an input file (C) to be present, but it does not have to be one of C.BASIC or C.BIOS - you’re welcome to write a standalone 8080 program yourself! How about C.FORTH or C.LISP?

In addition to the functionality you could expect from a program of this size, it allows importing files from the host file system (one by one, so you’ll have to be patient).

Remember the good old days and play (or let your kids play) Adventure (in the directory ADVENTUR); walking in a maze of twisty little passages all alike is easier than understanding the code!

NOTE: The KAYPROII.ZIP file originally came from http://www.retroarchive.org/cpm/os/KAYPROII.ZIP. For your convenience, we have included KAYPROII.ZIP in this entry. Both the make all and the make alt unzip that file, and the make clobber removes those files extracted from the KAYPROII.ZIP.

Author’s remarks:

This program emulates a complete Intel(r) 8080 processor, along with a teletype and a disk controller, just like at the start of the personal computers revolution (circa 1975).

It needs an initial memory image to do something usable, so along with it you will find two files: C.BASIC and C.BIOS. Rename C.BASIC to C (NOTE from the judges: running make will do this for you), run the emulator, and et voila! you have the public domain Palo Alto Tiny BASIC (by Li-Chen Wang), published in the very first volume of Dr. Dobb’s Journal.

Type using uppercase letters. Here are three example programs. Press Enter after each line:

    10 PRINT "Hello, world!"
    LIST
    RUN

    10 FOR A=1 TO 10
    20 PRINT A
    30 NEXT A
    LIST
    RUN

    10 INPUT A
    20 INPUT B
    30 PRINT A+B
    LIST
    RUN

Press Ctrl+Z to quit. By the way, the segmentation fault is normal at this point.

All good programmers started learning BASIC, now, what about a CP/M emulator?

Copy CPM64.COM to files named A and B (these will be the disk drives). Now rename the provided C.BIOS to C and run the emulator.

Now you have a running CP/M system!, with two files on A: drive, HALT.COM to stop the emulator (so it closes drives) and IMPORT.COM to introduce new files. The two files are created automatically by the provided C.BIOS.

To get a complete CP/M system, you will need the following files from the SOURCE directory:

To import them, you must run the emulator with an argument, by example:

    ./toledo2 DDT.COM

When the > prompt appears, do:

    IMPORT DDT.COM

When it ends, do HALT, so the file is closed, and you can start the same process with another file.

At this time I have tested successfully the following software from http://www.retroarchive.org:

Some programs require installation to configure the terminal, locate ANSI or VT-100.

What is an 8080?

It is simply the little brother of the Z80; it has no extended registers (AF', BC', DE', HL', IX or IY), no relative jumps, and no instruction beginning with CB, DD, ED or FD exists.

The flags are only S (Sign, bit 7), Z (Zero, bit 6), P (Parity, bit 2) and C (Carry, bit 0).

Porting it

It is easy if your platform has getch()/kbhit() and ANSI terminal:

Notice that you’ll have to do #include <conio.h> as well.

Also add the following to trap Ctrl-C:

    #include <signal.h>
    signal(SIGINT, SIG_IGN);

NOTE: this is what the alternate code is for!

NOTE from the Judges: in Unix like systems getch() is part of curses but this is not what is needed.

On PC/DOS you need to add ANSI.SYS to CONFIG.SYS.

In Unix the min 0 on stty is required but circa 2001 it was not required.

NOTICE to those who wish for a greater challenge:

If you want a greater challenge, don’t read any further: just try to understand the program via the source.

If you get stuck, come back and read below for additional hints and information.

How this entry works:

The l array contains the 64K memory; it is initialized with a boot image loaded from the C file. The program counter is the c pointer and registers are in o[]. The main loop reads every opcode and separates them in one of three common forms. A lot of ternary operators selects the instruction.

The following instructions do peripheral operation:

Memory addresses:

The BIOS is tailor made for this emulator, and helps to simplify it.

Other notes

Inventory for 2006/toledo2

Primary files

Secondary files

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