VERIFIED · 01.10.2026 AI help: yes reviewed by: teacher and psychologist · 2026-10-01

Grandpa's Machine: Pravetz and the 8-bit World

More than 40 years ago, Bulgaria made its own computers. They were called “Pravetz”. Today you will see how they worked and write a line of your own in the language BASIC — on a green screen like the ones from that time.

⏱ 10–15 min Explorer Grandparents' Machines · 1 Grades 4–5

You will be able to tell what the Pravetz 82 was, and to write and run a two-line program on a simulator of an old computer.

For parents: a one-page guide — dinner questions and an interview with a grandparent.

01Remember

You already know some things from earlier lessons. Think first, then open the answer.

What are the four things every computer does?

It takes in (input), works out (processing), remembers (memory) and shows (output).

Which memory forgets when the power goes off — the working memory or the storage?

The working memory (RAM) forgets. The storage keeps things even without power.

What is a bit?

The smallest piece of information — like a switch that is either on or off. We write it as 1 or 0.

02Story

There is a town in Bulgaria called Pravets. The Bulgarian computers called “Pravetz” got their name from it. They were designed by engineers at the Institute of Technical Cybernetics and Robotics of the Bulgarian Academy of Sciences. Most of them were built in the town of Pravets.

The first Bulgarian microcomputer was the IMKO-1. After it came the IMKO-2 and the Pravetz 8 series. One of the first in that series was the Pravetz 82. This is the machine we will call “grandpa's machine”.

What was inside a Pravetz 82?

A processor (the 6502) — it ran at 1 MHz. That is about one million tiny steps a second.
Working memory (RAM) — 48 KB.
Read-only memory (ROM) — 12 KB. The language BASIC was stored in it, so the computer “knew” it as soon as you switched it on.

The Pravetz 82 is an 8-bit computer. That means it works with eight “switches” (bits) at a time — numbers from 0 to 255. That is why old computers of this kind are called 8-bit.

48 KB is very little. A phone with 4 GB of memory has more than 80,000 times as much.

The Pravetz 82 was built to run the programs of the American computer Apple II. Many of the chips inside were Bulgarian or from Soviet makers. In Bulgaria, computers like these were used in schools and science institutes. The first ones had an ordinary television instead of a monitor.

⚠️ Where sources disagree

When you read about history, not every book and website says the same thing. Here are two examples:

When did serial production of the Pravetz 82 begin — in 1982 or in 1983? Some sources say the first, others the second.
When was the first IMKO-1 — in 1979 or in 1980?

So here we do not pick a side. We say both, and we ask: “Who wrote this, and how do they know?”

Not all Pravetz computers were the same. There was also a home computer, the Pravetz 8D, which is not like the Pravetz 82. And there were later 16-bit Pravetz computers — we will meet them in the next lesson.

Want to see more? Read with an adult, in the “Retro” section, the articles (in Bulgarian) about the IBM PC XT and Pravetz, the Pravetz 386 and the Oric Atmos and Pravetz 8D.

03Worked example

You switch on an old computer of this kind. A ] sign appears on the screen — that is how it is on the Apple II, and the Pravetz 82 has the same ROM memory and the same circuits. It says: “Type!” Here is how you give the computer a one-line program:

Input
You type on the keyboard: 10 PRINT "HELLO" and press RETURN — the key that says “the line is finished”.
Memory
The line starts with a number. So the computer does not run it at once. It remembers it in the working memory. The number tells it which place in the order the line has.
Processing
You type RUN. The processor takes the lines one by one, in number order: the smallest first.
Output
PRINT means “show”. HELLO appears on the screen.

INPUT

MEMORY

PROCESSING

OUTPUT

Two handy tricks. A line without a number runs at once. And programmers number lines in tens — 10, 20, 30. That way you can slip a new line numbered 15 in between 10 and 20 later.

04Try it

1 · Predict

If you type PRINT "HELLO" without a number in front and press RETURN — what happens? Choose before you check.

2 · Run: your green screen

This is our own imitation of the screen of an old computer. It has no programs or memory from a real machine. The green colour is like many computers of that time. Press an example, then RETURN. At the end type RUN.

]

It understands: PRINT "text", PRINT 2+3 (signs + − * / and brackets), RUN (go), LIST (show the program), NEW (start again), HOME (clear the screen). Make up words — do not type names, addresses or phone numbers.

3 · Change

Type the line numbered 20 first and the line numbered 10 after it. Type RUN. In what order do they appear? Why?
Slip a new line numbered 15 in between, for example 15 PRINT "HOW ARE YOU?". Type LIST, then RUN.
Press “⏻ Switch power off”. What happened to your program? Which memory forgets like this — working memory or storage?

05No screen: interview a grandparent

Do this only if your grandma or grandpa would enjoy it. If there is no grandparent nearby, ask another older adult you know. You need a sheet of paper and a pencil.

Ask: “Did you see a computer when you were little? Where was it and what did people do with it?”
Ask: “What was it called? Do you remember what it looked like — the screen, the keyboard?”
Ask: “Have you heard of Pravetz? Where did you meet one?”
Write down in a few words, or draw, whatever they tell you.

✋

Let your grandparent lead

If they do not remember — that is an answer too. If they do not want to talk, stop and thank them. Do not take photos or record unless they have allowed it. Do not post the story anywhere on the internet.

06Make your own: a program on paper

Make a “computer” out of paper strips.

Cut 4 strips. On each write a numbered line: 10 PRINT "...", 20 PRINT "...", 30 PRINT "..." and 40 PRINT "...".
Ask someone to shuffle them and scatter them. Then put them in order by number and read them out loud — like a computer.
Add a fifth strip numbered 25. Where does it go?

07What I learned

The Pravetz 82 is a Bulgarian 8-bit computer, built to run the programs of the Apple II.
A program is a list of numbered lines. The computer keeps them in memory and runs them in number order when you type RUN.
When the power goes off, the working memory forgets the program.

A computer keeps its program as long as there is power. And you — what do you keep in your memory from your grandparents' stories?

Check yourself

1. What does the computer do with a line that starts with a number?

runs it at once remembers it and runs it when you type RUN deletes it

2. You have line 20 and line 10. Which one runs first?

the one I typed first the one with the bigger number the one with the smaller number — line 10

3. The Pravetz 82 is a Bulgarian computer built to be like…

the American Apple II today's phone an electric typewriter

Skill badge: “I run a program in old BASIC”
It is yours when you can type two numbered lines on the simulator, run them, and explain why they come out in that order. There are no points and no rankings — only a skill.

08I have a question

Do you still have a question? Write it here. It goes to your parent, not to strangers. Your parent confirms their e-mail first.

The form is loading… If it does not appear, write your question on paper and show it to a parent or teacher.

·Sources

Title: Grandpa's Machine: Pravetz and the 8-bit World (DB-MD-01) · Author: Children's Library, East Accelerator Foundation · Source: original content, 2026; the green screen is our own code, with no programs from a real computer · Rights: CC BY-SA 4.0.
Title: Pravetz computers · Author: Wikipedia contributors · Source: en.wikipedia.org/wiki/Pravetz_computers · Rights: CC BY-SA 4.0 · Adaptation: the facts are retold in our own words and simplified for children; no text was copied.
Title: Applesoft BASIC · Author: Wikipedia contributors · Source: en.wikipedia.org/wiki/Applesoft_BASIC · Rights: CC BY-SA 4.0 · Adaptation: only the facts — the ] sign and that PRINT shows.
Title: Monochrome monitor · Author: Wikipedia contributors · Source: en.wikipedia.org/wiki/Monochrome_monitor · Rights: CC BY-SA 4.0 · Adaptation: only the fact that a “green screen” was common.
Title: История на компютри Правец (History of the Pravetz computers, in Bulgarian, 10.08.2021) · Author: A.Museum · Source: amuseum.bg · Rights: © amuseum.bg — the site asks to be cited by name; only facts were used (1983 for the Pravetz 82, televisions used as monitors).
Retro articles on kagami.bg (in Bulgarian): IBM PC XT and Pravetz · Pravetz 386 · Oric Atmos and Pravetz 8D.
Apple, Apple II and Applesoft are trademarks of their owners. “Pravetz” is a brand name. They are mentioned only to make clear which machine we mean; this lesson has no connection with them.
Licence: CC BY-SA 4.0 · Children's Library, East Accelerator Foundation, 2026. You may share and adapt this lesson if you credit the author and keep the same licence. Learning is free forever.