Overlay (programming): Difference between revisions

Revision as of 21:18, 6 August 2022

Revision as of 21:23, 6 August 2022

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==Example==

The following example shows the control statements that instruct the [[OS/360]] [[Linkage Editor]] to link an overlay program containing a single region, indented to show structure (segment names are arbitrary):

<pre>

INCLUDE SYSLIB(MOD1)

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and the new link replaced all of the old link's storage except for the Fortran COMMON area.

IBM introduced more general overlay handling<ref name="IBM_1963_IBJOB"/> in [[IBSYS]]/[[IBJOB]], including a tree structure and automatic loading of links as part of CALL processing.

In OS/360, IBM extended the overlay facility of [[IBLDR]] by allowing an overlay program to have independent overlay regions, each with its own overlay tree. OS/360 also had a simpler overlay system for transient [[Supervisor call|SVC]] routines, using 1024-byte SVC transient areas.

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