Lesson 1 · 1 of 20

Hello, world · Pascal

Your first Pascal program: WriteLn prints text and results to the console. Compile it with Free Pascal or run it with F9 in DMarlon Studio.

Pascal · Hello, world in DMarlon Studio: the example's code and its output in the terminal

A Pascal program starts with its name, program main;, and what it does goes between `begin` and `end.`, with a full stop marking where it finishes. Each statement ends with a semicolon.

`WriteLn` writes whatever you put inside the brackets to the console and moves to the next line. Text goes between single quotes, 'Hello, world!': it is a string. `Write` does the same without the line break, which is why Write('Two plus three is ') and WriteLn(2 + 3) end up on the same line.

Numbers go without quotes, and Pascal works out the sum before printing it: 7 * 24 comes out as 168. With commas, a single WriteLn prints several values one after another with nothing in between (you add the spaces inside the quotes). A WriteLn with no brackets prints an empty line.

Comments are not run: // comments out the rest of the line and { ... } wraps a comment that can span several lines. In DMarlon Studio, Pascal powers desktop apps built with Lazarus as well as the Console target, where this program runs with F9.

Code · main.pas

program main;{ The program runs from begin to the final end with a full stop. }begin  WriteLn('Hello, world!');  WriteLn('Welcome to Pascal.');  // Write stays on the same line; WriteLn moves to the next one.  Write('Two plus three is ');  WriteLn(2 + 3);  // Several values, separated by commas, in one WriteLn.  WriteLn('A week has ', 7 * 24, ' hours.');  WriteLn;  WriteLn('Goodbye!');end.

Output · fpc main.pas && ./main

Hello, world!
Welcome to Pascal.
Two plus three is 5
A week has 168 hours.

Goodbye!

Key points

The program goes between begin and end., with a full stop.
WriteLn prints and moves to a new line; Write does not.
Text goes between single quotes; numbers do not.
Commas separate several values in one WriteLn.
// and { } are comments.

Exercise

Make the program print your name and, on another line, how many minutes there are in a day (let Pascal work it out with 24 * 60).