Colon

The symbol :, pronounced “colon”, is used in Pascal in several ways:

• in an identifier declaration it separates the type
  • most notably in var sections
  • but also in const sections (in case of explicitely typed constants)
  • procedure and function parameters have a type, too
  • and return values of functions (including operator overloads)
  • as well as properties
  • in general, everywhere where a new identifier associated with some memory, is introduced (also custom structured type definitions)
• in case selectors it closes a match-list
• in label definitions the colon seperates the instruction from the label name
• also some routines, especially the Str, write and writeLn procedures accept further parameters via colon separated arguments
• Offset / segment separation under DOS Mem[$B800:$0000]

The following example shows the most prevalent usage scenarios:

program colonDemo(input, output, stderr);

procedure numberReport(const i: int64);
begin
    case i of
        low(i)..-1:
        begin
            writeLn('Your number is negative. ☹');
        end;
        1..high(i):
        begin
            // right aligns to a width of 24 characters
            writeLn(i:24);
        end;
        else
        begin
            writeLn('You''ve entered zero.');
        end;
    end;
end;

var
    i: int64;

begin
    writeLn('Enter a number:');
    readLn(i);
    numberReport(i);
end.

other remarks

• Colon appears in the assignment operator :=.
• In ASCII the character colon : has the value 58.

From the Free Pascal wiki, page "Colon", as it stood on 2022-08-06 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.