# Pascal
Pascal is a procedural programming language created by [Niklaus Wirth](niklaus_wirth.md) in 1970.

Pascal was a popular choice for microcomputers in the 70's and 80's, even more popular than C initially (C was still quite an UNIX-only language)
due to its simple design, which allowed fast simple single-pass compilers.

## Compilers
- [FPC](https://www.freepascal.org/) (Free Pascal Compiler): currently the most popular Pascal compiler with wide support
for different OSes and architectures, libre software.
- Turbo Pascal: old compiler for DOS systems, proprietary
- Delphi: proprietary, adds [OOP](oop.md) bloat

## Examples
### Hello world
```pascal
program HelloWorld;

begin
    WriteLn('Hello, World!');
end.
```

And then compile:
```
fpc hellopascal.pas
```

### Factorial
```pascal
{
Calculate a factorial on multiple languages: Pascal version
Compile with: fpc -O3 -S2 fact.pas
}
program Factorials;

{ qword = 64 bit unsigned type }
function FactorialRec(n, acc: qword): qword;
begin
    if n <= 0 then
        Result := acc
    else
        Result := FactorialRec(n - 1, acc * n);
end;

function FactorialIter(n: qword): qword;
begin
    Result := 1;
    while n > 0 do
    begin
        { The usage of C-like arithmetic assignment operators is possible with -Sc: }
        { Result *= n; }
        Result := Result * n;
        Dec(n); { equivalent to C's `--` operator }
    end;
end;

var
    n: qword;
    values: array of qword = (14, 5, 2, 10, 1, 18, 4);
begin
    Assert((FactorialIter(0) = 1) and (FactorialRec(0, 1) = 1));
    for n in values do
    begin
        WriteLn('Factorial of ', n, ' = ',  FactorialRec(n, 1));
    end;
end.
```

## Resources
- [Free Pascal Wiki](https://wiki.freepascal.org/Main_Page)
- *Why Pascal is Not My Favorite Programming Language* by Brian Kernighan, mostly of historic interest as almost all of the
flaws described in the article has been fixed by modern Pascal compilers. <https://www.lysator.liu.se/c/bwk-on-pascal.html>

## See also
- [Oberon](oberon.md)