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RPG IV

R – Report

P – Program

G – Generator

Version 4

History of RPG

• 1964: RPG - Report Program Generator• 1969: RPG II

– With release of System/3

• 1979: RPG III– Interactive programming– Database– Structured Programming

• 1988: RPG/400– Upgrade to RPG III

• 1994: RPG IV– Integrated Language Environment (ILE)– Modular Programming

Things that made RPG unique

• Program CycleRead a record

Loop until Eof

process the record

read a record

End of loop

• Indicators

Specifications

• Programs are organized in a series of specifications and appear in this order

Spec Type Description When Introduced

H Header (control) RPG

F File RPG

D Definition RPG IV

I Input RPG

C Calculation RPG

O Output RPG

P Procedure RPG IV

H-Specs (Control Specifications)

• Default formats (eg. Date formats)• Changes to normal processing modes

– Eg changing the internal method that the program uses to evaluate expressions

• Special options to use when compiling the program

• Language enhancements that effect the entire program

H Datfmt(*ISO) Timfmt(*HMS)

F-Specs

Position Use Position Use

7-16 File Name 23-27 Record Length

For program described

17 File Type

(I, U, or O)

36-49 Device

Disk, Printer, Workstation

18 File Designation

Blank – output file

F – Full Procedural

P – Primary File (logic cycle)

S – Secondary File (logic Cycle)

R – Record address file

T – Table

44-80 Keywords

(see appendix A of text book)

22 File Format

F – Program Described

E – Externally Described

D-Specs (Definition)

• Standalone variables

• Named constants

• Data Structures

• Prototypes

• Procedure Interfaces

D-Specs

• Data name– 15 characters– Must start with a letter of the alphabet or $, # or @– Remaining characters must be letters, numbers, _, #,

$ or @

• Declaration Type– DS – Data Structure– C – Constant– PR – Procedure– PI – Procedure Interface– S – Standalone Variable

D-Specs

• Length– Length of Data

• Decimal Places– Number of decimal places

• Data type

I-Specs (Field Definition)

• Used to define fields in the filePos Use Pos Use

7 – 16 Filename 36 Data Type

17 – 18 Sequence

NS – if no sequence required

2 digit number if sequence is required

37 – 46 Field Location

19 Number

Leave blank

47 – 48 Decimal Positions

Required by numeric fields

20 Option

Leave blank

49 – 62 Field Name

6 characters up to RPGIII

14 characters RPG IV

21 – 22 Record id (indicator)

C-Specs (Calculation)

• Program logic!

Factor1 Opcode Factor2 Result Indicators

• RPG IV introduces free form RPG for C-Specs

O-Specs (Output)

• Define the output of the program. May be report definitions or database.

Pos Use Pos Use

7-16 FileName 30 - 43 Field Names

17 Type

D-Detail

H-Header

E-Exception

T-Total

53 – 80 Constants / Edit Word

30 – 39 Exception Name 47 – 51 End Position

40 – 45 Skip and Space Entries 52 Edit code

P-Specs

• Will discuss later in the course

Add

qty1 add qty2 qty3

or

add qty qty3

Sub

qty1 sub qty2 diff

or

sub qty diff

Mult

pricemult qty sales

or

mult 0.14 sales

Div

sales div qty price

or

div qty sales

Read

• Reads the next record from a database object (sequential read)

read sales 99

will ‘turn on’ indicator 99 if the end of file is reached.

EXCPT (EXCEPT)

• Writes output to printer files

excpt format

IF

• RPG, RPGII, RPGIII– IFEQ, IFNE, IFLE, IFLT, IFGT, IFGE, etc– Ends with endif

qty ifeq 0

endif

• RPGIV free format– If– Ends with endif

If qty = 0;

Endif;

Do Loops

• RPG, RPGII, RPGIII– DOWEQ, DOWNE, DOUEQ, DOUNE etc– Ends with ENDDO

Qty Doweq 0enddo

• RPGIV free format– DOW, DOU– Ends with ENDDO

Dow qty < 0;enddo;

Itempgm Demo