DATASSim

Simulator for DATAS machine language

About this project

DATAS is an educational, artificial machine language designed in the 1970s to demonstrate how machine code works.

It had no real hardware, i.e. it did not belong to a real computer, but was a theoretical machine that was treated as a "machine" for educational purposes.

Its typical use was to teach Fortran or other high-level languages, so that students could understand what was going on "under the hood".

I discovered it in the Hungarian translation of the book Algorithms and their computer solutions ¹. This is the only source, I couldn't find anything about it on the Internet.

Note

If anyone has any information or memories about this language that they can share, I will be happy to take them and include them in the documentation.

I deviated from the description in the book in that the third digit from the right of the word consisting of eight decimal numbers (the tens place value of the second, D1 group) indicates the sign, so that negative numbers can also be handled. The memory cells can be commented on, as this is an educational model.

A special feature is that the memory cells can be commented on, as this is an educational model.

Copyright (C) 2025 Pozsár Zsolt [email protected]

Features

features
version	v0.1
licence	EUPL v1.2
language	en
user interface	CLI
programming language	Borland Turbo Pascal 3.x
architecture	ix86, Z80
OS	CP/M and DOS (and others, see comments in the source.
internal memory	100 word size cell (00-99)
word format	8 decimal number (00 00 00 00 - 99 19 99 99)
instructions	10
example scripts	4 scripts
load from file	program in text format with comments
save to file	memory content in text format with comments
export to file	memory content to binary file
import to file	memory content from binary file
other utility programs	source code to binary file converter

Screenshots

Startup screen

Help about instructions

The commands

The program can be controlled with the following command line commands.

name	operation
break [AA|-]	set, get and reset breakpoint address
comment AA Jump\ to\ 12|-	add or remove a sigle-line note for AA address
deposit AA D0 D1 D2 D3	store D0-3 value at AA address
dump AA CN	print the value of memory cell number CN from AA
examine AA	examine value at AA address
export filename.bin	export memory content to a binary file
fill AA CN D0 D1 D2 D3	fill the memory cell number CN from AA with the value D0-3
help [command]	help with using the program
import filename.bin	import memory content from a binary file
load filename.lst	load source code
quit	exit the simulator program
reset	reset simulator
run [AA]	run program from AA address
save filename.lst	save source code
step	run program step-by-step from AA address
trace [on|off]	turn tracking on and off

The instructions

The following instructions can be used in the machine code program.

name	AA	D0	D1	D2	D3	operation
	dd	00	sd	dd	dd	(AA)=D0 D1 D2
ADD	dd	01	dd	dd	dd	(D3)=(D1)+(D2)
SUBTRACT	dd	02	dd	dd	dd	(D3)=(D1)-(D2)
MULTIPLY	dd	03	dd	dd	dd	(D3)=(D1)*(D2)
DIVIDE	dd	04	dd	dd	dd	(D3)=(D1)/(D2)
BRANCH	dd	05	00	00	dd	jump to D3
	dd	05	01	dd	dd	if D2<0 then jump to D3
	dd	05	02	dd	dd	if D2>0 then jump to D3
HALT	dd	06	00	00	00	stop at AA address
READ	dd	07	dd	00	00	read a value to D1
WRITE	dd	08	dd	00	00	write a value from D1
SQRT	dd	09	dd	00	dd	(D3)=sqrt(D1)
ABS	dd	10	dd	00	dd	(D3)=

Note: AA: address D0: operation code D1-3: operands (Dx): value at Dx address s: sign of the number [0/1, +/-]

Source file format

; Calculate the square root of 23*100
01 05 00 00 52 ;jump to address 52
50 00 00 01 00 ;store 100 at address 50

Footnotes

1. Algorithms and Their Computer Solutions by Lucio Artiaga and LLoyd D. Davis (1972 Charles E. Merill Publishing Company) ↩