DDS Keyword Reference [Illustrated] [Paperback]

James Coolbaugh (Author)

Book Description

Publication Date: April 1, 1999

AS/400 Programmers and systems administrators will get quick, at-your-finger-tips information about all DDS keywords for physical, logical, display, printer, and ICP files. Each keyword is briefly explained, with syntax rules and examples showing how to code the keyword. This book has all the pertinent information to provide an easy alternative to IBM's bulky DDS reference manual.

Editorial Reviews

About the Author

James Coolbaugh is president of JDC Computer Services, Inc., of Medina, Ohio. He has more than 20 years of experience in data processing and for the past 16 years has worked exclusively with the System/38 and the AS/400. Jim is the author of SQL/400 by Example and DDS Programming for Display and Printer Files, second edition (both from 29th Street Press). He has written various articles about AS/400 topics.

Excerpt. © Reprinted by permission. All rights reserved.

Introduction

With the introduction of the System/38 in the early 1980s, IBM provided a mechanism for creating files from external source specifications called Data Description Specifications (DDS). From DDS source, you can create file objects (object type *FILE on the AS/400) that high-level language (HLL) programs can then use. This approach eliminates the need to hard-code file specifications in every HLL program that uses a specific file. Creating files from DDS source is called external file definition.

The A-Specification Format

You can use DDS to create physical, logical, display, printer, and ICF files. All file types are coded using a format called the A-specification (A-spec). The A-spec is a combination of fixed-format and free-format definitions used to specify a particular file.

The A-spec consists of three areas: the conditioning zone, the definition zone, and the keyword zone.

Conditioning Zone

The conditioning zone of the A-spec encompasses column 7 through column 16. Within the conditioning zone for display, printer, and ICF files, you can use indicators to control when fields or keywords are active for the file (indicators are not valid for physical and logical file specifications). You can place up to three conditioning indicators (e.g., 99 or N99) and a single letter code (A for “and” or O for “or”) in an A-spec to combine the conditions of two or more consecutive specifications into a single, complex condition.

Definition Zone

The definition zone spans columns 17 through 44 of the A-spec. This zone is coded strictly in fixed format, in which the meaning of the letters, digits, and symbols depends on the column in which you place them. The definition zone, as its name implies, lets you define data fields (input, output, or both) and record formats.

Keyword Zone

From column 45 through column 80 of the A-spec, you can plug in any number of keywords in free-format style. Like command parameters, keywords for the most part consist of an uppercase name (of up to 10 characters) followed by a value enclosed in parentheses.

This Book’s Focus

This desktop guide focuses on the keyword zone. Literally hundreds of keywords exist, and the ones you can use in a particular situation depends on the type of file you’re creating: physical, logical, display, printer, or ICF. Separate sections of this guide cover all the keywords for each of the five file types. Each section discusses all keywords for that file type in alphabetical order. Each keyword discussion lists all the keyword’s parameters, explains the use of the keyword, and shows an example of how to code the keyword and parameters in the A-specs.

Product Details

• Paperback: 248 pages
• Publisher: 29th Street Pr; illustrated edition edition (April 1, 1999)
• Language: English
• ISBN-10: 1583040420
• ISBN-13: 978-1583040423
• Product Dimensions: 8.7 x 7 x 0.5 inches
• Shipping Weight: 12 ounces
• Average Customer Review: 4.0 out of 5 stars  See all reviews (1 customer review)
• Amazon Best Sellers Rank: #3,299,730 in Books (See Top 100 in Books)

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Most Helpful Customer Reviews

1 of 1 people found the following review helpful:

4.0 out of 5 stars Very handy reference, April 5, 2000

By A Customer

This review is from: DDS Keyword Reference (Paperback)

A good book for the AS400 programmer. Quick & easy access to DDS information. The book includes keywords explanation for PF, LF, DSPF and ICF files, It also includes all the syntax rules and detailed coding examples, a useful desktop reference book