# Play with Docker and Pascal > Can you run 30-year-old Pascal code today? Yes! This guide shows you how to use Docker and the Free Pascal Compiler (FPC) to compile and execute your legacy Turbo Pascal programs. ---  **TL;DR** This article revives 30-year-old Turbo Pascal source code (pulled from the old SWAG archive) using the `signumtemporis/fpc` Docker image to compile `.pas` files into Windows executables with zero local install, running both a "Hello World" and an old school byte-to-binary conversion function written back in 1992. Good old memories... During my studies (in 1991-1993), I was a huge fan of Turbo Pascal 7.0. It was the first language that I really learned, and I loved it so much. I used to spend dozens of hours behind my computer writing anything and everything. If you still remember that time, Turbo Pascal 7.0 was used to create executables for MS-DOS. The idea for this article came after the one written on [assembly language](/blog/docker-assembly): is it possible in 2023 to run Pascal code written 30 years earlier?  The first thing to do was to find some old source code and to do that, I went back to the **S**ource**w**are **A**rchive **G**roup; known as **SWAG**. The following parametrized query will retrieve some code I've published 30 years ago: . Out of nostalgia, I've also copied these sources here: . ## Hello world Please run `mkdir C:\tmp\pascal && cd C:\tmp\pascal` in a MS-DOS console to create a folder called `pascal` and jump in it. Please create a new file called `Hello.pas` with this content: **Hello.pas** ```pas begin writeln('Hello world! I''m a Turbo Pascal source code'); end. ``` As you know, Pascal is a compiled language and should then be compiled into an `.exe`. The command below will do this: ```bash $ docker run -it --rm -v %CD%:/app -w /app signumtemporis/fpc:cross.x86_64-win64.slim Hello.pas Free Pascal Compiler version 3.2.2 [2021/12/10] for x86_64 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: Win64 for x64 Compiling Hello.pas Linking Hello.exe 2 lines compiled, 0.1 sec, 32432 bytes code, 1508 bytes data ``` Our executable has been created. Time to start it by running `Hello.exe`: ```bash $ Hello.exe Hello world! I'm a Turbo Pascal source code ``` Voilà, we've successfully created our first Pascal code in 2023. *This blog has a small collection of such "run language X without installing it" articles: [Java](/blog/docker-java), [Python](/blog/docker-python) and [PHP](/blog/docker-php-run-script-or-website).* > **Docker CLI reminder:** > > As a reminder, the used Docker run commands are (almost always the same): > > * `-it` to start Docker interactively, this will allow the script running in the container to ask you for some prompts f.i., > * `--rm` to ask Docker to kill and remove the container as soon as the script has been executed (otherwise you'll have a lot of exited but not removed Docker containers; you can check this by not using the `--rm` flag then running `docker container list` on the console), > * `-v %CD%:/app` to share your current folder with a folder called `/app` in the Docker container, > * `-w /app` to tell Docker that the current directory, in the container, will be the `/app` folder > * then `signumtemporis/fpc:cross.x86_64-win64.slim` which is the name of the Docker image to use and, finally, > * `Hello.pas` i.e. our source file (the fpc image seems to not request to specify the `fpc` executable; just the source file). ## Convert a number to a byte Let's try something a *little more complex* than just *Hello world*; a conversion function to determine the byte representation of a positive number *(please be comprehensive; it was a school assignment 😄)*. I wrote this function in 1992 (published in the *SWAG* in 1997): Create the `Byte2Bin.pas` file on your disk with this content: **Byte2Bin.pas** ```pas Function Byte2Bin (Chiffre : Byte) : String; Var I, Temp : Byte; St : String; Begin St := ''; For I := 7 Downto 0 do Begin Temp := (Chiffre and (1 shl I)); If (Temp = 0) then St := St + '0' Else St := St + '1'; End; Byte2Bin := St; End; begin WriteLn( Byte2Bin(197) ); end. ``` > **SHL for Shift left one position:** > > The `shl` instruction will shift the number from one byte left. And compiled it: ```bash $ docker run -it --rm -v %CD%:/workspace signumtemporis/fpc:cross.x86_64-win64.slim Byte2Bin.pas Free Pascal Compiler version 3.2.2 [2021/12/10] for x86_64 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: Win64 for x64 Compiling Byte2Bin.pas Linking Byte2Bin.exe 20 lines compiled, 0.1 sec, 32656 bytes code, 1508 bytes data ``` As you can see in the source code, the idea was to show the binary representation of `197` and, yes!, it's indeed `11000101`. Still in 2023. ```bash $ Byte2Bin.exe 11000101 ``` OK, so the point of running TP7 code in 2023 is minimal and useless, but it is well fun to see it still works. Same idea, different language: I've also played with [Python](/blog/docker-python) and [Java](/blog/docker-java) using the exact same "zero local install" Docker approach.