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Chapter 1: Introduction

This book is intended to help users of:

to migrate applications to Server Express 1.1 or Server Express 2.0. This book guides you through the code and build changes that you might need to make to migrate existing applications.

You should read the Getting Started book before reading this or any other documentation provided with this product.

The rest of this chapter briefly describes how the approach to creating an application with this product differs from your previous product. The remaining chapters are reference chapters where you can look up particular features and find outline advice on migrating them.

Product differences that do not require you to make any changes are not, in general, mentioned in this book; these include new features of the product which do not require any specific migration considerations. Read the Getting Started book for an overview of the new features of this product.

You should read the on-disk file readme.1 in the /docs directory of your installation, which lists any problems which have been found with this release of Server Express. You should also refer to your Read This First document for important product information.

1.1 Where You're Coming From

Migrating from previous products can lead to problems when recompiling source code or executing programs, or in understanding the differences in the interface and behavior. You should bear in mind the information in the following sections when migrating programs.

1.1.1 From Server Express 1.0 to Server Express 1.1 or 2.0

If you are moving applications from Server Express 1.0 to Server Express 1.1 or 2.0, you can recompile source code and execute programs created on Server Express 1.0. See the chapters New Features in Server Express 1.1 and New Features in Server Express 2.0 for information on the new features provided in 1.1 and 2.0.

1.1.2 From Object COBOL V4.1 for UNIX

In Server Express, all the facilities that you are used to - notably source-level debugging, also called "animation" - can be used on an all executable file types (that is, on. .int, and .gnt files, system executables, and the new callable shared object files).

1.1.3 From COBOL V4.0 for UNIX

In addition to the changes that were introduced in Object COBOL V4.1 for UNIX, Server Express enables you to create, debug and execute applications that use Object-Oriented COBOL syntax extensions.

1.1.4 From Other Products

You can migrate applications from older versions of Micro Focus COBOL for UNIX. For COBOL V3.x systems, see the previous sections. You can migrate applications from COBOL V1.3 for UNIX, as there is still a very high degree of source code compatibility (see below), but the architecture of the product, applications and user interfaces has changed.

If you are migrating applications from Micro Focus Net Express, you will notice a high degree of common technology, specifically the support for threaded applications and HTML syntax support, and many other new features. However, Server Express uses character-based interfaces, so the user interfaces for most development tools are markedly different.

1.2 Code Compatibility

The following section describe how source code created using earlier versions of COBOL for UNIX is handled by Server Express.

1.2.1 Source Code

COBOL source code developed in previous products should compile cleanly with Server Express. You need to be aware of certain changes in the behavior of Compiler directives and cob flags; these changes are referred to later in this book.

1.2.2 Debugging

You cannot debug an application compiled with an earlier version of Micro Focus COBOL. You need to recompile the application.

1.2.3 Executable Code Formats

Although source code written for previous products (see above) should compile cleanly on this product, the .gnt files, .o files and system executable files produced by these systems are not compatible with Server Express. You need to rebuild your application.

.int files are compatible unless they contain object-oriented code.

1.3 Data Files

Data files created using earlier versions of Micro Focus COBOL for UNIX are supported by this product.

1.4 Undefined Results

The value returned by some COBOL operations is specified in the Language Reference as undefined; for example, dividing by zero, or using data that does not conform to a picture clause. If you were to examine the values actually returned by these operations, you would find that they differ according to the executable file format and the COBOL system on which the program was compiled. For example, a divide-by-zero operation might return a different value in an intermediate code program to that returned in a generated code program.

You should ensure that the results or logic of your program do not depend on the results of operations specified as giving undefined results. For example, as the result of a divide-by-zero operation is unpredictable, you should always use the ON SIZE ERROR phrase if you want a specific action or procedure to be performed depending on this result.

1.5 Performance Considerations

This product is geared to improving the efficiency of the applications it creates, and should provide a noticeable improvement in execution speed over applications built with previous products. As no two applications are the same, it is difficult to give precise details of what performance improvements you can expect.

Copyright © 2000 MERANT International Limited. All rights reserved.
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