HP SunSoft Pascal 4.0 Manual do Utilizador descarregar pdf (Página 102)

78 Pascal 4.0 User’s Guide

Using extern Option to Share Routines

If a program or module calls a procedure not deﬁned in that unit, you must

declare it with either the extern or external routine option. For instance, in

the previous example, the procedure proc is deﬁned in shrvar_mod.p, but

used in shrvar_prog.p. Thus, it is declared as external in

shrvar_prog.p. Also, proc must also be deﬁned as public in

shrvar_mod.p, which is the default.

Usinginclude Files to Share Variables and Routines

The include ﬁle contains the declarations for the program. Placing all

program declarations in a single ﬁle makes your program more consistent and

easier to maintain.

To use this feature, place the number sign character (#) in the ﬁrst position of a

line immediately followed by the word include, and then a ﬁle name

enclosed in angle brackets (< and >) or double quotation marks ("). The

different enclosures (<> and "") affect the search order for ﬁles. The syntax for

the #include directive is determined by cpp(1).

When the compiler encounters the #include in the input, it inserts the lines

from the included ﬁle into the input stream.

The commands to compile and

execute shrvar_prog.p and

shrvar_mod.p

hostname% pc shrvar_prog.p shrvar_mod.p

shrvar_prog.p:

shrvar_mod.p:

Linking:

hostname% a.out

From MAIN, before PROC: 1

From PROC : 1

From MAIN, after PROC : 2

1 2 ... 97 98 99 100 101 102 103 104 105 106 107 ... 332 333

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HP SunSoft Pascal 4.0 Manual do Utilizador Página 102