{$mode objfpc}

uses
  SysUtils, FGL;

type
  TIntList = specialize TFPGList<Integer>;

procedure SieveOfEratosthenes(n: Integer; var primes: TIntList);
var
  sieve: array of Boolean;
  i, j: Integer;
begin
  // Create a sieve array with all elements set to true
  SetLength(sieve, n + 1);
  for i := 2 to n do
    sieve[i] := True;

  // Mark non-primes using the Sieve of Eratosthenes algorithm
  for i := 2 to Trunc(Sqrt(n)) do
  begin
    if sieve[i] then
    begin
      for j := i * i to n do
      begin
        if j mod i = 0 then
          sieve[j] := False;
      end;
    end;
  end;

  // Store prime numbers in the output list
  for i := 2 to n do
  begin
    if sieve[i] then
      primes.Add(i);
  end;
end;

var
  primes: TIntList;
  i: Integer;

begin
  // Create a new TIntList to store prime numbers
  primes := TIntList.Create;

  // Generate prime numbers using Sieve of Eratosthenes
  SieveOfEratosthenes(10000, primes);

  // Print the last three prime numbers
  Writeln('Last three prime numbers:');
  for i := primes.Count - 3 to primes.Count - 1 do
    Writeln(primes[i]);

  // Free the TIntList
  primes.Free;
end.
by

Pascal online compiler

Write, Run & Share Pascal code online using OneCompiler’s Pascal online compiler for free. It’s a straightforward, accessible way to learn and experiment with Pascal programming right from your browser. OneCompiler supports modern Pascal syntax and provides a ready-to-use editor for immediate execution.

About Pascal

Pascal is a procedural programming language developed in the 1970s by Niklaus Wirth. It was designed to encourage good programming practices and structured programming. Pascal is widely used in teaching computer science fundamentals and has influenced many modern languages.

Sample Code

The following is a simple Pascal program that prints a greeting:

program HelloWorld;
begin
  writeln('Hello, OneCompiler!');
end.

Taking inputs (stdin)

OneCompiler’s Pascal editor supports stdin through the I/O tab. Here’s an example that reads a user's name and prints a greeting:

program GreetUser;
var
  name: string;
begin
  readln(name);
  writeln('Hello, ', name, '!');
end.

Syntax Basics

Variables

var
  age: integer;
  name: string;
  score: real;
  flag: boolean;

Data Types

TypeDescription
integerWhole numbers
realFloating-point numbers
charSingle character
stringSequence of characters
booleanTrue or False

Conditionals

if score >= 50 then
  writeln('Pass')
else
  writeln('Fail');

Loops

For loop

for i := 1 to 5 do
  writeln(i);

While loop

i := 1;
while i <= 5 do
begin
  writeln(i);
  i := i + 1;
end;

Repeat-Until loop

i := 1;
repeat
  writeln(i);
  i := i + 1;
until i > 5;

Procedures and Functions

procedure SayHello;
begin
  writeln('Hello!');
end;

function Add(a, b: integer): integer;
begin
  Add := a + b;
end;

This guide provides a quick reference to Pascal programming syntax and features. Start coding in Pascal using OneCompiler’s Pascal online compiler today!