IBM AS/400 manual Naming Files, Types of File Descriptions

Types of File Descriptions

RPG program

File name - FILEY

Device = SEQ

FILEY

File type =

DEVICE

Device type =

PRINTER

Figure 128.		Associating a file name with a display file description
Although	the	file name and	file type are coded	in the	RPG	program,
you can	change the type		of file or the device	used	in a	program
the program. To find out how, see “Overriding and Redirecting						File I
Output”	on	page 273.

Naming Files

On the

AS/400

system,

files

are

made up of members. These

files are

into libraries.

The convention

for naminglibraryfiles-name/fileis-name.

In an ILE RPG program, file names are identified in positions 7 thro

description

specifications.

File

names

can

be

up

to

ten

characters l

unique.

You do not qualify the file

name

with a

library

within

a

program.

system searches

the

library

list

associated

with

your

job

to

find

to change the name, member,

or specify a particular library, you c

override

command.

See

“Overriding

and

Redirecting File

Input

and

Outpu

page 273

for more

information

on

file

overrides.

Types of File Descriptions

When identifying the file description your						program will be using, you
whether it is		a program-described			file or	an externally described
¹ For	aprogram-described file		, the	description		of the fields are coded
RPG	source	member	on input	and/or	output	specifications.

The description of the file to the operating system includes info where the data comes from and the length of the records in the

¹For anexternally described file , the compiler retrieves the description o

fields		from	an external file-description which was created using D
SQL commands.			Therefore, you do not have to code the			field	desc
input	and/or		output specifications within the RPG source member.
The	external		description includes information about where the data
such	as	the	database or		a specific device, and a	description
its	attributes.			The file	must exist and be accessible from		the
you	compile		your	program.

Externally described files offer the following advantages:

¹ Less	coding	in programs. If the	same file	is used by many	progr
can	be defined once to the operating system and used by				all t
This	practice eliminates the need to code input and output				speci
RPG	programs	that use externally	described	files.

Chapter 14. Defining Files263