Sharable Images

A shareable image is a special type of image that allows several processes to use functions stored in a single image file concurrently. For instance, most higher-level language compilers are supplied with shareable images containing their library routines. When generating main object files, the language compilers do not include code for their library routines in the main object, but instead include calls to the routines in the shareable image.

As an example, every C language program that uses the printf() function need not contain its own internal copy of the printf() code; they can all use the common routine in the C Runtime Library shareable image. When considering the number of main programs and the number of library routines used within them, considerable disk space and physical memory can be saved.

Sharable images can (if properly designed) undergo considerable change without relinking all of the main images that use them. Features can be added, and problems in library routines can be fixed by replacing a single shareable image file.

Note 

OpenVMS uses a combination of compilers and linkers to produce executable files, as opposed to systems that do not use linkers. This means that modules written in a variety of languages can be combined into a single executable image. The OpenVMS Procedure Calling Standard ensures that modules written in different languages can work together.

OpenVMS shareable images are roughly equivalent to dynamic link libraries (DLLs) as implemented within the Microsoft Windows environment.



Getting Started with OpenVMS(c) A Guide for New Users
Getting Started with OpenVMS: A Guide for New Users (HP Technologies)
ISBN: 1555582796
EAN: 2147483647
Year: 2005
Pages: 215

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