Historians Recreate Source Code of First 4004 Application

mcpublic writes "The team of 'digital archaeologists' who developed the technology behind the Intel Museum's 4004 microprocessor exhibit have done it again. 36 years after Intel introduced their first microprocessor on November 15, 1971, these computer historians have turned the spotlight on the first application software ever written for a general-purpose microprocessor: the Busicom 141-PF calculator. At the team's web site you can download and play with an authentic calculator simulator that sports a cool animated flowchart. Want to find out how Busicom's Masatoshi Shima compressed an entire four-function, printing calculator into only 1,024 bytes of ROM? Check out the newly recreated assembly language "source code," extensively analyzed, documented, and commented by the team's newest member: Hungary's Lajos Kintli. 'He is an amazing reverse-engineer,' recounts team leader Tim McNerney, 'We understood the disassembled calculator code well enough to simulate it, but Lajos really turned it into "source code" of the highest standards.'"

Only 1024?

Volume in drive C is NTSWIM100
  Volume Serial Number is 1CB0-998C

  Directory of c:\WINDOWS\system32

08/23/2001 10:00 AM 114,688 calc.exe
                              1 File(s) 114,688 bytes
                              0 Dir(s) 50,615,652,352 bytes free

Re:Only 1024?

Would you rather the MS guys spend time seeing if they can force their 114k application down into 10k, or perhaps writing an operating system that doesn't suck?

It'd be an improvement if MS did either.

Re:Only 1024?

Floating-point math doesn't fix itself. Let's not be hard on Microsoft when:

Python 2.5.1 (r251:54863, Oct 30 2007, 13:54:11)
[GCC 4.1.2 20070925 (Red Hat 4.1.2-33)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 10.1-10-0.1
-3.6082248300317588e-16

and...

$ perl
printf("%s\n", 10.1-10-0.1);
-3.60822483003176e-16

and...

$ php
<?php
echo (10.1-10-0.1);
?>
-3.6082248300318E-16

Note that the answers vary across languages too...

Those were fun

Somewhere around 1975 or 1976 I wrote software for a 4004 (using a teletype connected to a modem connected to a mainframe someplace that had the assembler) to run a X-Y table. You would place a wafer with thick-film resistors on it and it would test each one to make sure it was within tolerance and if it wasn't it would mark it with magnetic ink. I think we were probably still using the infamous 1702 EPROMs but there might have been something newer at that time.

but...

does it run linux? ... lame!

And best of all

You can still run it on the latest Intel x86 chips. ;)

slashdot headline, 2057:

"Historians Recreate Source Code of First 404 Error Message"

(truth be told, quick scanning the headlines, that's what my brain registered)

I hate to be a pendantic jerk, but...

"...an authentic calculator simulator..."

What the hell is an authentic simulator?

Re:I hate to be a pendantic jerk, but...

Your hand?

zing!

Re:I hate to be a pendantic jerk, but...

Na way man, Jill never needs flowers or taken out to dinner. She's better than authentic!

Quickly -- someone send this to MS

Quick, someone send this over to the folks who wrote Excel!

The output

Hello world!

the output is

58008

Commander Keen

I once reverse engineered the classic id software game Commander Keen. John Carmack did some cool stuff in that code.. each sprite had two function pointers in it, one was called when the sprite came into contact with another sprite, the other was called every frame to animate the sprite (he called it the "think" function). When you killed a monster the sprite was replaced with a "body" which was just like a sprite but had a few less fields (so it took up less memory). One of the neatest things he did was use this exact same framework of sprites and bodies to animate the "static" parts of the game. For example, the color coded doors that you have to get the key cards to open were sprites with a contact function that checked if the player had the right key card, at which time they would "die" and be replaced by a body that had a think function would make them slide out of the way.

For anyone who would like to take a look, I've put the re-engineered source code [insomnia.org] up.

Re:Commander Keen

Carmack's code is always interesting. Most famously, there's the infamous square root approximation from Quake [codemaestro.com]. But I'm still impressed by the original Doom render loop, with it's self-modifying code.

The loop is drawing columns (vertical slivers of wall). It needs to interpolate between two things: the input wall texture, and the output part of the screen. Carmack uses something like Bresenham's line drawing algorithm to do this, but because the 386 has such a limited register set, he stores the fractional increment in an immediate attached to the "addl" instruction:

doubleloop:
    movl ecx,ebp // begin calculating third pixel
patch1:
    addl ebp,12345678h // advance frac pointer
    movb [edi],al // write first pixel
    shrl ecx,25 // finish calculation for third pixel
    movl edx,ebp // begin calculating fourth pixel
patch2:
    addl ebp,12345678h // advance frac pointer
    movl [edi+SCREENWIDTH],bl // write second pixel
    shrl edx,25 // finish calculation for fourth pixel
    movb al,[esi+ecx] // get third pixel
    addl edi,SCREENWIDTH*2 // advance to third pixel destination
    movb bl,[esi+edx] // get fourth pixel
    decl [loopcount] // done with loop?
    movb al,[eax] // color translate third pixel
    movb bl,[ebx] // color translate fourth pixel
    jnz doubleloop

and elsewhere... :)

movl ebx,[_dc_iscale]
    shll ebx,9
    movl eax,OFFSET patch1+2 // convice tasm to modify code...
    movl [eax],ebx

A similarly impressive trick is used to draw floors, where 3D interpolation is required because each texture needs to be crossed diagonally, not vertically. I never understood how Doom drew floors until I looked at the code, and I still think it's deep magic. And that's without even mentioning the BSP code!

How to build a CPU -- transistor level up!

Take a look at this set of videos from MIT's 6.004 Computation Structures [mit.edu] class. They basically walk through the design of a simple 32-bit CPU from transistors, to gates, to functional blocks, to a full processor.

Anyway, reading about how hard it was to recreate the source code from the 4004 makes me wonder how easily we could find source code for some apps from even a decade ago. Lots of companies have gone bankrupt / discontinued products / been sold / etc, and we all know that lots of people aren't good about backing up their code. It's neat to go to the Linux Kernel Archives and look at the Historic Linux sources [kernel.org].

--
Educational microcontroller kits for the digital generation. [nerdkits.com]

Amazing!

'He is an amazing reverse-engineer,' recounts team leader Tim McNerney, 'We understood the disassembled calculator code well enough to simulate it, but Lajos really turned it into "source code" of the highest standards.'

No disrespect to Lajos, but have we really fallen so far in programming standards that it's considered "amazing" to disassemble a 1024 byte program? Back in my day (and stay the hell off my lawn!) we used to disassemble programs all the time. I reverse engineered the operating system for a computer I developed for because we wanted to hook into places that weren't accessible.

Disassembly is apparently a lost art in these decadent days of some programmers never using anything but scripting languages (e.g., Java, Python, Perl) and having no clue what goes on under the hood.

Re:Amazing!

"Programs must be written for people to read, and only incidentally for machines to execute." - Abelson & Susman

From a theoretical point of view, assembly knowledge isn't particularly useful because it doesn't lend itself to rigorous analysis (the "science" part of "computer science"). From a practical point of view, since very few programs are written in assembly language anymore, knowledge of it has limited utility. Further, from a practical point of view, I'd much rather deal with a programmer who can explain his work in terms of data structures and algorithms than one that is stuck thinking in terms of registers and memory locations.

There is certainly a place for assembly knowledge*. It's just a niche, and not a particularly important one anymore. Meanwhile, there are lots and lots of diverse applications for the theory they teach you in those classes instead of assembly. In my own work, I've had to bust out the graph theory way more often than I've had to bust out my knowledge of asm tricks for fast line-rendering...

*) Interestingly enough, one of those places is inside the language runtimes of high-level languages. There are usually lots of neat tricks inside those things (eg: using the NaN space of double-precision floats to store unions of floats and 51-bit integers without extra variant tags!)

Re:Amazing!

Sometime in the early 70s, a Honeywell division, one of our steady clients, called with a strange request. They had built a small number of special machines for the Navy. Now the Navy wanted more. Honeywell had the circuit drawings and the bootable tape (which they got from the Navy). They had no documentation (not even the instruction set). They asked us to rebuild the code. We did. Dick.

Backups?

So you are saying that nobody had the source backed up anywhere? We have come so far, yet haven't gone very far at all...

55378008

'leet speak first turned the world upside down as a joke about "BOOBLESS". I wonder if the 4004 could run a softporn text adventure game like that.

My 4004 Project

[reminisce] Back in 1972 I did the first uP project at Cornell using a 4004. No assembler, no emulator, not even a PROM programmer. Just a list of op-codes and a sheet of paper that I wrote H or L for every bit of the PROM. That got sent to a electronics distributor that would program the part. Unfortunately, I can't claim to have done the first OPERATING uP project at Cornell! [/reminisce]

Where's the update?

I found a buffer overflow. Exploit code to follow...

vista calc.exe properties

File version 6.0.6000.16386
Size: 172 KB (176,128 bytes)

kinda puts things in perspective, doesn't it?

ah, "progress"

1024 bytes? Try 1024 bits

In 1998, to celebrate the 50th anniversary of an early computer, The University of Manchester ran a programming contest [computer50.org] on the Baby Mark I, which sported 32 words of 32 bits each and a very limited instruction set: you couldn't even ADD.

There were, of course, many other ideas apart from those of the prizewinners: programs to compute square roots, fibonnaci sequences, trig functions and encryption algorithms. A program which clears the store totally, another which simulates bellringing. A tamagochi program, a cipher machine simulator, and so on.

The winning entry was a noodle-timer program.

I have the original 4004 reference guide

I have the original 4004 reference guide (blue cover), scored during an early Wescon convention in 1970. I looked at this and said -- "Oooh, a whole hexadecimal digit on a single chip. That's going to change things."

People used to consider square wave logic charts a programming tool back then, too.

Somebody call the cops!

It is obvious this Kintli fellow has violated the DMCA ... or is it the SPCA ... anyway he broke
the law by reverse engineering a piece of commercially sold software. Since this was not done for
the purpose of interoperability, the law should be called in!

Asimov's The Feeling of Power

How has no one mentioned this yet? - Don't blame me too much, I just copied and pasted from: http://downlode.org/Etext/power.html [downlode.org]

The Feeling Of Power
by Isaac Asimov

Jehan Shuman was used to dealing with the men in authority on long-embattled earth. He was only a civilian but he originated programming patterns that resulted in self-directing war computers of the highest sort. Generals, consequently listened to him. Heads of congressional committees too.

There was one of each in the special lounge of New Pentagon. General Weider was space-burned and had a small mouth puckered almost into a cipher. He smoked Denebian tobacco with the air of one whose patriotism was so notorious, he could be allowed such liberties.

Shuman, tall, distinguished, and Programmer-first-class, faced them fearlessly.

He said, "This, gentlemen, is Myron Aub."

"The one with the unusual gift that you discovered quite by accident," said Congressman Brant placidly. "Ah." He inspected the little man with the egg-bald head with amiable curiosity.

The little man, in return, twisted the fingers of his hands anxiously. He had never been near such great men before. He was only an aging low-grade technician who had long ago failed all tests designed to smoke out the gifted ones among mankind and had settled into the rut of unskilled labor. There was just this hobby of his that the great Programmer had found out about and was now making such a frightening fuss over.

General Weider said, "I find this atmosphere of mystery childish."

"You won't in a moment," said Shuman. "This is not something we can leak to the firstcomer. Aub!" There was something imperative about his manner of biting off that one-syllable name, but then he was a great Programmer speaking to a mere technician. "Aub! How much is nine times seven?"

Aub hesitated a moment. His pale eyes glimmered with a feeble anxiety.

"Sixty-three," he said.

Congressman Brant lifted his eyebrows. "Is that right?"

"Check it for yourself, Congressman."

The congressman took out his pocket computer, nudged the milled edges twice, looked at its face as it lay there in the palm of his hand, and put it back. He said, "Is this the gift you brought us here to demonstrate. An illusionist?"

"More than that, sir. Aub has memorized a few operations and with them he computes on paper."

"A paper computer?" said the general. He looked pained.

"No, sir," said Shuman patiently. "Not a paper computer. Simply a piece of paper. General, would you be so kind as to suggest a number?"

"Seventeen," said the general.

"And you, Congressman?"

"Twenty-three."

"Good! Aub, multiply those numbers, and please show the gentlemen your manner of doing it."

"Yes, Programmer," said Aub, ducking his head. He fished a small pad out of one shirt pocket and an artist's hairline stylus out of the other. His forehead corrugated as he made painstaking marks on the paper.

General Weider interrupted him sharply. "Let's see that."

Aub passed him the paper, and Weider said, "Well, it looks like the figure seventeen."

Congressman Brant nodded and said, "So it does, but I suppose anyone can copy figures off a computer. I think I could make a passable seventeen myself, even without practice."

"If you will let Aub continue, gentlemen," said Shuman without heat.

Aub continued, his hand trembling a little. Finally he said in a low voice, "The answer is three hundred and ninety-one."

Congressman Brant took out his computer a second time and flicked it. "By Godfrey, so it is. How did he guess?"

"No guess, Congressman," said Shuman. "He computed that result. He did it on this sheet of paper."

"Humbug," said the general impatiently. "A computer is one thing and marks on a paper are another."

"Explain, Aub," said Shuman.

"Yes, Programmer. Well, gentlemen, I write down seventeen, and just undernea

1024 Bytes? Bah!

How about 256 bytes for a 3D rotating parallax tunnel fly-through [256b.com] !!!

LS

John Titor called......

....and is requesting that you start on the IBM 5100 (the flux capacitor broke).

Actually, only 939 bytes of ROM.

Want to find out how Busicom's Masatoshi Shima compressed an entire four-function, printing calculator into only 1,024 bytes of ROM?

There were 85 left over bytes at the end (filled with NOP), so it was really only 939 bytes of ROM.

Re:uhhhh...

That is the correct answer - all modern calculators are descended from a competitor's model which incorrectly calculated 9+9 to be 18.

Re:uhhhh...

You could read the documentation. You want 9+ 9+ = At the end you did 9+9+9 You could look at what's on the tape. IHBTHIND

Re:Something is wrong......

Of course if you had bothered to read the article, you'd know that it doesn't work like todays calculators but like the old adding machines:

"The electronic calculators that accountants used 35 years ago worked differently than the familiar four-function calculator we use today. These were designed to behave much like mechanical adding machines of the 1960's. After every number you want to add to the total, you need to press +, so = doesn't work like you'd expect. Here are some examples:

To add three numbers: 61 + 79 + 83 + = (if you forget the last +, the 83 won't get added)
To subtract two numbers: 2007 + 1971 - =
To multiply two numbers: 125 x 5 = (this is more like we're used to)
To divide two numbers: 625 / 5 = "

Re:I wrote a PC BIOS INT10 video display driver in

And by a whole lot more you mean 4 times more, right?