The Probert Encyclopaedia of Science & Technology

DBASE IV

Ashton-Tate's dBase IV was a greatly enhanced version of dBase III Plus and provided more facilities for the power user to develop turnkey applications without the need to write code. The Control Center was an extension of The Assistant in dBase III Plus and was much more powerful. The Control Center let users open and close files, create views and reports, and run programs that provide the novice end-user with easier access to dBase files. Reports, forms, and queries produced through the Control Center generate dBase source code which can be edited. The Query By Example panel of the Control Center displays a visual representation of the data file. By specifying criteria within a view, you can select records, display fields, or combine data from several database files. Without leaving dBase IV, you can run DOS operations such as CHKDSK or DIR through the DOS window. dBase IV can save 47 indexes to a single file. Index files are automatically created with every database file. Each time you open a database file, the associated index file is automatically opened. This is much easier than opening data and index files separately as required in dBase III Plus. The new Application Generator writes all code necessary for incorporating forms, reports, and files into a turnkey application. The dBase/SQL command programming language lets you create, modify, or query databases using SQL commands. You can issue SQL commands from the dot prompt and include SQL procedures within dBase programs. This allows access to dBase files by mainframe and minicomputer users who are familiar with SQL. When dBase IV executes SQL commands, it first translates the code from SQL to actual dBase source code. This translation prevents users from accessing external SQL code. Enhancements to the programming language let you create two dimensional arrays, multi-child relationships, and data validation support. A transaction processing procedure creates a transaction log file of changes made to
se files. This helps avoid data loss due to power shortages, inadvertent reboots, and system failures.

When used with Ashton-Tate's Chart-Master, the dBase/ Chart-Master Bridge let users graph data files. The report and form generator are WYSIWYG, so it is easier to develop forms and reports. The screen painter displays memo fields through a window, and a pseudo compiler increases the speed of all commands issued at the dot prompt up to ten times faster than in dBase III Plus. Memo fields can be searched, copied to and from, and are available for program control. This lets you program
dBase IV to perform automatic queries on memo fields. Built-in printer drivers support bold, italics, underlining, superscript, and subscript printing.
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