Associating Files with Input/Output Devices

SPECIAL. Figure 126 on page 262 shows a file description specification f display (WORKSTN) file FILEX.

*..

1 ...

+...

2 ...

+...

3 ...

+

... 4 ...

+...

5 ...

+...

6 ...

+...

7 ...

+...

*

FFilename++IPEASFRlen+LKlen+AIDevice+.Keywords+++++++++++++++++++++++++++++

FFILEX

CF

E

 

 

 

WORKSTN

 

 

 

 

 

 

 

 

Figure 126. Identifying a Display File in an RPG Program

 

Note

that

it is

the

file name, not the device name

(specified

in po

 

42)

which points to the OS/400

file

description that

contains

the

speci

 

the

actual

device.

 

 

 

 

 

 

 

 

The

RPG device

types

correspond to the above file

types

as follows:

 

 

 

 

 

 

 

 

Table

16. Correlation of RPG Device Types with AS/400 File Types

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RPG Device

Type

 

 

AS/400 File

Type

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DISK

 

 

 

database, save,

DDM files

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PRINTER

 

 

 

printer

files

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WORKSTN

 

 

 

display,

ICF files

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SEQ

 

 

 

tape, diskette,

save,

printer, database

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SPECIAL

 

 

 

N/A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 127 illustrates the association of the RPG file name FILEX, as c Figure 126, with a system file description for a display file.

RPG program

File name = FILEX Device = WORKSTN

FILEX

Device type =

DISPLAY

Figure

127. Associating a file name with a display file description

 

 

 

 

At

compilation

time,

certain

RPG

operations

are valid only for a

specifi

device

name.

In

this

respect,

the

RPG

operation

is

device

dependent.

of

device dependency

is that

the

EXFMT

operation

code is

valid

only

f

WORKSTN

device.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Other

operation codes are device independent, meaning that they

can

b

any

device

type.

For

example,

WRITE

is

a

device-independent

operation.

The

SEQ

Device

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The

device SEQ is an independent device type. Figure 128 on page 263

 

the

association

of

the RPG

file name FILEY

with

a

system

file

descri

sequential device. When the program is run, the actual I/O device is description of FILEY. For example, the device might be PRINTER.

262 ILE RPG for AS/400 Programmer's Guide

Page 285 Page 287
Page 286
Image 286
IBM AS/400 Compilation Time Certain, Operation Device Dependent Device dependency Is that, Operation Code is Valid Only
Page 285 Page 287

AS/400 specifications

The IBM AS/400, now known as the IBM iSeries, is a midrange computer system that has been a cornerstone of enterprise computing since its introduction in 1988. Designed to provide a robust platform for business applications, the AS/400 is celebrated for its reliability, scalability, and integrated database capabilities.

One of the key features of the AS/400 is its Integrated Operating Environment, which blends hardware and software resources seamlessly. This integration allows businesses to execute diverse workloads, ranging from traditional applications to modern web-based services, all on a single platform. The operating system, OS/400 (now IBM i), offers a rich set of APIs and tools for developers, simplifying application development and management.

Another standout characteristic of the AS/400 is its built-in database, DB2 for i. This powerful relational database management system allows for efficient data handling and provides advanced features such as support for SQL, XML, and JSON, making it easier for businesses to manage their data and integrate it with other systems. The database's tight integration with the operating system enables high performance and security.

In terms of scalability, the AS/400 can accommodate small businesses as well as large enterprises, with the ability to support hundreds of users simultaneously. Its architecture allows for easy upgrades in hardware, meaning that organizations can scale their systems without replacing the entire infrastructure.

Security is another critical attribute of the AS/400. With a sophisticated security model, it offers built-in user authentication, access control, encryption, and auditing capabilities to protect data and applications from unauthorized access.

The AS/400 also supports multiple programming languages, including RPG, COBOL, Java, and PHP, giving organizations the flexibility to choose the development tools that best fit their needs. This diversity helps maintain legacy applications while also developing new ones that leverage modern technologies.

Moreover, the platform supports both traditional green-screen interfaces and modern graphical user interfaces, allowing organizations to transition smoothly into contemporary user experience paradigms.

Overall, the IBM AS/400 stands out as a resilient, flexible, and secure computing platform that enables organizations to effectively manage their business operations, streamline processes, and adapt to changing market demands. Its unique combination of integrated features and capabilities ensures that it remains relevant in today's fast-paced technology landscape.
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