Standard Pascal Libraries and files including abilities

Pascal Libraries (Unit)

Free Pascal && Virtual Pascal compilers provide standard units such as 

Crt, Strings, Windows, Sysutils, Dos, Printer, Graph,... 

This is sub-programs coded for programers. Crt Unit provides procedures

and functions to act text screen mode such as Crt.Clrscr, ClrEoL, Gotoxy,

Strings Unit contains procedures and functions which act chars

Pascal Compilers give us a lots of standard units, i.e Virtual Pascal provides 

24 std units :)

However, coders must create several modules which contain other procedures

and functions.

Unit consture:

// Commonly save as Unitname.pas

Unit [Unitname];

interface

uses

[Units_needed_to_use]; // i.e Windows, Sysutils,...

// varibles, data types, procedure and function names of [Unitname];

implementaion

// varibles needs to use, full sources of procedures && functions of [Unitname] and more...

end.

Press Ctrl - F9 to compile [Unitname].pas on Borland/Turbo envs. 

Result: [Unitname].tpu :)

To be continued....