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RPG IV

RPG IV. Defining Data with Definition Specifications - Chapter 3. Objectives :. Define work fields, data structures and other data items Set the initial value for data items Distinguish among program variables, literals and constants. Definition Specifcations.

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RPG IV

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  1. RPG IV Defining Data with Definition Specifications - Chapter 3

  2. Objectives: • Define work fields, data structures and other data items • Set the initial value for data items • Distinguish among program variables, literals and constants

  3. Definition Specifcations • Define all fields in your program • Specify name, length, and type • Input Specifications define fields from database • Definition Specifications define work fields or stand-alone fields

  4. Numeric Literal • The literal may include a decimal point and/or sign. • The sign must be the left most character of the literal. • The literal may include digits 0 thru 9. • The literal should never contain commas, dollar signs, or percent signs. • The literal 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 fields definition • The value is indicated using a numeric or character literal or a figurative constant

  8. Zoned Decimal and Packed Decimal • Zoned decimal requires a full byte of storage • Packed-decimal use a compressed storage format • Integers and binary numbers require even less memory than the decimal data types do

  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

  10. Indicator Data Type • Refered to in other languages as Boolean data type • Code N in column 40 • You can initialize to *ON or *OFF

  11. Defining Constants • A named constant differs from a standalone in two respects: • Its value never changes during processing • It is defined with no specified length • Code the letter C, for constant, in column 24 • Enter the value in the Keywords area

  12. Defining Data Structures • Subdivide fields into subfields • Change field data types • Data structure has two parts, the data structure header and the 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

  13. Defining Data-Structure Subfields • Absolute notation, uses From and To to indicate the beginning and ending postions of the subfield • Length notation, leaves From blank and enters the subfield length in the To positions • Length notation is prefered

  14. Overlapping Subfields • Locations of subfields can overlap • Absolute notation clearly indicates the overlap with the From and To • Length notation uses the keyword OVERLAY

  15. Points to Remember • RPG IV requires you to define all fields your programs will use • Input fields are defined using Input Specifications and standalone fields are defined using Definition Specifications • You can use the keyword INZ to assign a value to a field

  16. Points to Remember (cont) • 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, and boolean • Data structures let you subdivide fields into subfields and redefine fields

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