| Developing COBOL Applications | Packaging Applications | |
Application Server supplements your operating system to provide the additional functionality that you, as a business programmer, need in an operating system.
Note: Application Server was formerly known as the Operating Systems Extensions (OSX). Any references to OSX or to Operating Systems Extensions in this manual can be read as Application Server.
Application Server provides an operating environment that enables you to build applications that are:
Application Server consists primarily of a set of functions targeted at the Server environment and a set of functions targeted at the Client environment. For more information on the Application Server product see the section Your Application Server Product later in this chapter.
Figures 2-1 and 2-2 compare the Application Server approach with a more conventional architecture.
Figure 2-1 illustrates a traditional operating environment without
Application Server. An application written for UNIX cannot be ported
easily to OS/2 or Windows. In effect, it requires a significantly
different program using a different set of tools. 
Figure 2-2 illustrates the Application Server architecture. In this environment, a single application runs across different operating environments without change.
A basic principle of the Application Server architecture is that
Application Server provides a common base (level playing field) for your
applications. That is, regardless of the software and hardware environment
your application will eventually run in, you develop your application for
a single environment. That environment is the Application Server
environment. 
Your Application Server product contains a copy of the COBOL run-time system, with Application Server components in your operating system's standard object format. This enables you to target your application at environments where you might want to relink your run-time system.
Licensing:
Any component of your Application Server product can be shipped, in any
form, on to your users to support your applications, provided you conform
to the license agreement that accompanies this product. This is explained
in detail in your Getting Started.
The following Application Server components are available on DOS, Windows, OS/2, and UNIX:
| Run-time Environment | Provides an environment for running COBOL programs. It can load intermediate code files and generated code files dynamically. That is, each program is loaded only when it is called. It can run the same intermediate code across all environments, without change. |
| Fileshare Version 2 | Provides rapid network I/O by compressing I/O requests into packets and sending them across network lines. |
| Call-by-Name Routines | Routines called from your program that provide many operations not available in COBOL itself. |
| Common Communications Interface | Provides a standard mechanism for communicating over networks using a variety of protocols. |
The following Application Server Integration components are available on DOS, Windows, OS/2, and UNIX:
| Application Configuration System | Enables applications to make use of a standard configuration technique to control their behavior. |
| Banner Program | Displays screens of static information, usually associated with a menu (displayed by the Menu Handler). |
| Help Program | Provides a convenient mechanism for displaying help information for your application. |
| Linein Program | Provides a simple mechanism for applications to accept a text string within the Menu Handler environment. |
| Menu Handler | Displays and processes menus. The Menu Handler, called from your program, enables you to present a sophisticated configurable menu system with a minimal amount of programming. |
| Name Program | Provides a convenient mechanism for specifying file-names in a manner consistent with Workbench and Object COBOL for UNIX. |
The COBOL Run-time System provides the essential run-time support for:
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| Developing COBOL Applications | Packaging Applications | |