HP SunSoft Pascal 4.0 - Manual (Page 100)

76 Pascal 4.0 User’s Guide
5
Using Program Units
The program unit is the source program with the program header. It has the
following syntax:
< program unit > ::= < program heading > < declaration list > < program body >
Each program you write can have only one program unit. The program body
is the first code that Pascal executes.
Using Module Units
A module unit is a source program that does not have a program header. It
has the following syntax:
< module unit > ::= [ < module heading > ] < declaration list >
The module heading contains the reserved word module followed by an
identifier:
< module heading > ::= [ 'module' < identifier > ';' ]
For example:
This is a legal module heading. The module heading is optional.
Sharing Variables and Routines Across Multiple Units
Pascal supports three methods of sharing variables and routines between units:
•
include files
•
Multiple variable declarations
•
extern/define variable declarations
These methods are not mutually exclusive; for example, you can declare a
variable as either
extern or define in an include file.
The following sections describe these methods.
module sum;