Sage-ST ^TM ENVIRONMENT

To better understand how to use the Sage-ST ^TM system, it is helpful to understand how it is put together, how it evolved. It is strongly recommended that you read the introduction before proceeding.

Sage-ST ^TM refers to the actual set of packages and procedures containing the Ada code. Sage-ST ^TM contains libraries of reusable code for the Ada programmer to provide database and other capabilities for inclusion within an application system. These libraries include lower level packages for such functions as terminal and file I/O, data movement, bit manipulation, number conversion, string manipulation, etc. These packages are used by higher level packages of Sage-ST ^TM , but are supplied to the user for convenience in application development.

The higher level procedures include such capabilities as sorting, database manipulation, form, menu and window presentation, communications, and others. The standard application often requires very few lower level procedures, but extensive use of the upper level procedures.

In any system, we want a high degree of cohesion and a low degree of coupling. Cohesion refers to how closely elements within a package are related to each other. Coupling refers to how much one package depends on another. Sage-ST ^TM packages are highly cohesive, but at first glance it appears to have a great deal of coupling between elements.

Sage-ST ^TM consists of many packages with a great variety of functions. At the lowest level (e.g., MoveLib, DosLib, Terminal, Files, etc.) there is a very low degree of coupling among packages. These are the "nuts and bolts" of the Sage-ST ^TM system. But it's pretty difficult to build something from scratch out of nuts and bolts, so Sage-ST ^TM has higher level packages which, although coupled to the underlying packages, form frequently used components. At the highest level, Sage-ST ^TM packages exhibit a high degree of coupling with underlying packages but offer systems that can be dropped into place in your code. Note that although a package frequently exhibits coupling with the underlying, low-level packages, packages on the same level exhibit very little coupling.

The various levels give you, as the developer, a greater degree of flexibility and control over your code. Sometimes a "canned" system will be appropriate, providing a great time savings. However, this requires you to accept the system "as is". Sometimes the requirements of the customer will be such that every aspect of the system must be customized. It will be necessary for you to build that system using only nuts and bolts and possibly a few components, maybe not even using Sage-ST ^TM packages at all. It is your choice; nothing is forced upon you. Because Sage-ST ^TM is simply Ada code you are limited only by your skills and the Ada language itself. SUBTOPICS

Terminology
Keyed Fields and Indexes
Renaming Relations
Memory Record
System Limits
Portability Go Back To Sage-ST TABLE OF CONTENTS

Sage-ST TM ENVIRONMENT

Sage-ST ^TM ENVIRONMENT