Pascal Online: Free Pascal Editor and Compiler

The Pascal editor works right in the browser, and programs compile and run on the server — no compiler install needed. Send a link, and two people can work on a problem together: in an interview, or walking through a solution side by side. Free, no sign-up.

Open the Pascal editor
Free, no sign-upHow to run a live coding interview in PascalCollaborative code editors compared

Code sample

program Primes;
var
  n, i, j: integer;
  isPrime: boolean;
begin
  n := 30;
  for i := 2 to n do
  begin
    isPrime := true;
    for j := 2 to i div 2 do
      if i mod j = 0 then isPrime := false;
    if isPrime then write(i, ' ');
  end;
  writeln;
end.

Output

2 3 5 7 11 13 17 19 23 29

What the editor does

  • The Free Pascal 3.2 compiler: the program compiles and runs on the server, with compile errors and output visible right away.
  • Nothing to install: the editor, with Pascal syntax highlighting, works in the browser on any computer.
  • Real-time collaborative editing: up to 5 participants in one session, with edits and cursors visible instantly.
  • The problem statement is written in Markdown right in the session, next to the code.
  • The task bank is open without an account. After a free sign-in: your own tasks, an interview mode with timers, and session history.

How to run the interview

  1. Click "Run an interview" — the session is created with a sample program.
  2. Describe the task in Markdown and send the link: the other participant needs no sign-up.
  3. Work on the problem together: run the program after each step, and discuss compile errors and output — a convenient way to walk through a solution piece by piece.

Typical interview tasks

  • Find all primes up to N by trial division or the Sieve of Eratosthenes, and compare which approach is faster.
  • Compute the GCD of two numbers with Euclid's algorithm — by subtraction and by remainder.
  • Sort an array with bubble sort or insertion sort and count the number of swaps.
  • Check whether a string is a palindrome, ignoring spaces.
  • Find the sum and the digit count of a natural number using div and mod.
  • Find the maximum element in each row of a two-dimensional array.

Limitations

  • This is Free Pascal, not PascalABC.NET: features available only in PascalABC.NET will not compile.
  • There are no autotests for Pascal — verify the result with output: print the answer for several inputs and compare it with what is expected.
  • Compilation is limited to 10 seconds, and a run to 3 seconds and 64 KB of output.

FAQ

Which compiler is used?
Free Pascal 3.2. The program compiles and runs on the server, so there is nothing to install.
Will code from PascalABC.NET run?
Yes, as long as it does not use features available only in PascalABC.NET: Free Pascal compiles standard Pascal.
Can I enter keyboard input (readln)?
Yes. Type the data into the «Input (stdin)» field above the output — on Run, readln reads it as if it were typed. The field is shared by everyone in the session.
Can two people work together?
Yes. Send the session link — up to 5 participants can work in one editor, with edits visible in real time.
Do I need to sign up?
No. Create a session and start writing code right away. The task bank is open without an account too. Signing in is needed for your own tasks and history: without it the session is not saved, but the code can be copied.

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