Pascal (idea)

Under parameter, rp was unsure how Pascal referred to its subroutines, functions, procedures, or whatever they were called.

Pascal has two types of what most 'normal' programming languages* call the same thing...

function UpCaseStr(S: string): string;
var
  I: Integer;
begin
  for I := 1 to Length(S) do
  if (S[I] >= 'a') and (S[I] <= 'z') then
  Dec(S[I], 32);
  UpCaseStr := S;
end;

begin
  writeln UpCaseStr("AbCdEfGhIj");
end;

This code fragment (partially borrowed from the Delphi 2.0 online help for function) displays what a function does. It returns a single value, and allows the function to be called in-line, allowing ease of coding. The S is a parameter passed to the function.

procedure NumString(N: Integer; var S: string);
var
  V: Integer;
begin
  V := Abs(N);
  S := '';
  repeat
    S := Chr(N mod 10 + Ord('0')) + S;
    N := N div 10;
  until N = 0;
  if N < 0 then
    S := '-' + S;
end;

var MyString:string;

begin
  NumString(8,MyString);
  writeln "That number, "+MyString+", is now a string.";
end;

This code fragment shows how a procedure differs. Firstly, it cannot be called inline. Secondly, it shows the difference between the two parameters. The first, the number, is a value parameter: only the value is sent to the procedure, as the parameter was in the function. The second, the string, is a reference parameter: the location of the string in memory (and thus the actual string itself) is passed to the procedure.

Personally, I feel this is a poor example of the ability of a procedure, since it has one reference parameter/output, and could have been coded as

function NumString(N: Integer;):string;
var
  V: Integer;
  S: string;
begin
  V := Abs(N);
  S := '';
  repeat
    S := Chr(N mod 10 + Ord('0')) + S;
    N := N div 10;
  until N = 0;
  if N < 0 then
    S := '-' + S;
  NumString:=S;
end;

begin
  print "That number, "+NumString(8)+", is now a string.";
end;

. Procedures are better in many cases, since you have more control over it: you can have multiple outputs, an input that changes, or no output at all. But functions are much neater.

*: QBasic uses subroutines and functions. That isn't a normal programming language at all.

Thanks to gorgonzola who pointed out that its write or writeln in pascal, not print... I'm in perl mode again!