Presentation © Copyright 2002, Bryan Meyers Defining Data with Definition Specifications Chapter 3.

Presentation © Copyright 2002, Bryan Meyers

Defining Data with Definition Specifications

Chapter 3

Programming in RPG IVThird Edition

2

Objectives

• Define work fields, data structures and other data items

• Identify the appropriate data type for data items

• Set the initial value for data items

• Distinguish among program variables, literals and constants


3

Definition Specifications

• Define all fields in your program• Definition specifications define work fields

(standalone variables)– Input specifications define fields from database– S in position 24 indicates standalone variable

• Specify name, length, and decimal positions (if any)

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D TotalDue S 7 2D CtyStZip S 40


4

Numeric Literal

• May include a decimal point and/or sign

• Sign must be the left most character of the literal

• May include digits 0 thru 9

• Should never contain commas, dollar signs, or percent signs

• Must not be enclosed in apostrophes


5

Character Literals

• To indicate that a value is a character literal simply enclose it with apostrophes


6

Figurative Constants• *BLANK(S)

– Fills a character field with blanks

• *HIVAL– Fills a character with X’FFFF

(all bits on)– Fills a numeric field with all 9s

and + sign• *LOVAL

– Fills a character with x’000 (all bits off)

– Fills a numeric field with all 9s and - sign

• *ZERO(S)– Fills a numeric field with

zeros

• *ALL– Causes a string to be

repeated in a field• *OFF

– Character value of ‘0’• *ON

– Character value of ‘1’• *NULL

– Used with pointers


7

Assigning Initial Values to Data

• Specify the value using the INZ keyword in the field definition

• The value is indicated using a literal or a figurative constant

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D MaxLimit S 7 2 INZ(10500.00)D CompName S 40 INZ(‘Kay Elmnop Enterprises’)D HighLimit S 7 2 INZ(*HIVAL)


8

Zoned vs. Packed Decimal

• Zoned decimal requires a full byte of storage– Data type S in position 40

• Packed decimal use a compressed storage format– Data type P in position 40

• Integers and binary numbers require even less memory than the decimal data types do– Data type I (integer)– Data type U (unsigned integer)– Data type B (binary)

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D TotalDue S 7S 2D TotalDue2 S 7P 2D UpDown S 5I 0D RecCount S 10U 0


9

Date, Time, and Timestamp

• Timestamp is a combination of date and time

• Define a standalone field, put a D (for dates), T (for times) and Z (for timestamp) in column 40– Do not specify length or decimal positions

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D EnrollDate S DD StartTime S TD TransTime S Z


10

Indicator Data Type

• Referred to in other languages as Boolean data type

• Code N in column 40

• Must be a single byte

• You can initialize to *ON or *OFF

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D InpError S N INZ(*OFF)


11

Defining Constants

• A named constant differs from a standalone in two respects– Value never changes during processing– Defined with no specified length

• Code the letter C, for constant, in column 24• Enter the value in the Keywords area

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D FICA C .0765D ExVicePres C 'John Adams'D PhoneEdtWd C '( ) - 'D IndDay C D'1776-07-04'


12

Defining Data Structures

• Subdivide fields into subfields• Change field data types• Data structure has two parts

– Data structure header– Definition for the subfields

• DS coded in 24-25 on D spec signals the beginning of a data structure

• Enter name of data structure in 7-21*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D OptName DSD SubfieldA 3 0D SubfieldB 5 2


13

Defining Data Structure Subfields

• Length notation– Leaves From blank and enters the subfield

length in the To positions

• Absolute notation– From and To indicate the beginning and

ending positions of the subfield

• Length notation is preferred


14

Overlapping Subfields

• Locations of subfields can overlap• Length notation uses the keyword OVERLAY

– Absolute notation indicates the overlap with the From and To

*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... 8DName+++++++++++ETDsFrom+++To/Len+IDc.Keywords+++++++++++++++++++++++++++++D DSD Phone 10 0D AreaCode 3 0 OVERLAY(Phone)D Exchange 3 0 OVERLAY(Phone:4)D LocalNbr 4 0 OVERLAY(Phone:7) //Using OVERLAY with *NEXTD DSD Phone 10 0D AreaCode 3 0 OVERLAY(Phone)D Exchange 3 0 OVERLAY(Phone:*NEXT)D LocalNbr 4 0 OVERLAY(Phone:*NEXT)


15

Points to Remember

• RPG IV requires you to define all fields your programs will use

• Input fields (from files) are defined using Input Specifications

• Standalone fields are defined using Definition Specifications

• You can use the keyword INZ to assign a value to a field


16

Points to Remember

• Figurative constants are built-in literals with specified values

• Definition Specifications are used to define named constants as well as standalone fields

• RPG IV supports many data types– Character, numeric, date, Boolean, etc.

• Data structures let you subdivide fields into subfields and redefine fields

Presentation © Copyright 2002, Bryan Meyers Defining Data with Definition Specifications Chapter 3.

Documents

Transcript of Presentation © Copyright 2002, Bryan Meyers Defining Data with Definition Specifications Chapter 3.