https://gunkies.org/index.php?action=history&feed=atom&title=Overlay 2026-05-12T08:33:34Z Revision history for this page on the wiki MediaWiki 1.30.1 https://gunkies.org/w/index.php?title=Overlay&diff=26810&oldid=prev 2022-06-30T16:03:49Z

<p>Jnc moved page <a href="/wiki/Broadcast" title="Broadcast">Broadcast</a> to <a href="/wiki/Overlay" title="Overlay">Overlay</a> without leaving a redirect: Bah, created at wrong name</p> <table class="diff diff-contentalign-left" data-mw="interface"> <tr style="vertical-align: top;" lang="en"> <td colspan="1" style="background-color: white; color:black; text-align: center;">← Older revision</td> <td colspan="1" style="background-color: white; color:black; text-align: center;">Revision as of 16:03, 30 June 2022</td> </tr><tr><td colspan="2" style="text-align: center;" lang="en"><div class="mw-diff-empty">(No difference)</div> </td></tr></table>

Jnc https://gunkies.org/w/index.php?title=Overlay&diff=26809&oldid=prev 2022-06-30T16:03:04Z

<p>Next top entry on &#039;Wanted pages&#039; for me</p> <p><b>New page</b></p><div>'''Overlays''' are a [[programmer|programming]] technique for dealing with reduced availability of [[main memory]] - either because of a limited [[address space]] (as in the [[PDP-11]], towards the end of its life), or because the machine just did not have much (very common in the early days of computers).<br /> <br /> The program to be 'overlaid' was split up into tranches, called 'overlays', of which only one (or a limited number) were directly available to the [[Central Processing Unit|CPU]] at a time. When the program needed to transfer (via either a [[jump]], or a [[subroutine]] call) to an overlay that was not currently accessible, progress had to stop momentarily while that overlay was made accessible (perhaps by reading it in from [[secondary storage]]).<br /> <br /> Overlays perform the same basic function as the later [[virtual memory]] ('jam three gallons into a one-gallon bucket'), but do so explicitly, not automatically and invisibly.<br /> <br /> ==External links==<br /> <br /> * [https://minnie.tuhs.org/cgi-bin/utree.pl?file=2.9BSD/usr/man/man5/a.out.5 a.out (5)] - this and the next entry describe the supports for overlays in the later PDP-11 [[BSD]]s<br /> * [https://minnie.tuhs.org/cgi-bin/utree.pl?file=2.9BSD/usr/man/man1/ld.1 ld (1)]<br /> * [https://minnie.tuhs.org/cgi-bin/utree.pl?file=2.9BSD/usr/doc/2.9_kernel.ms Changes in the Kernel in 2.9BSD] - describes use of overlays in the [[2.9BSD]] [[kernel]]<br /> <br /> [[Category: Software Concepts]]</div>

Jnc