Editing DECtape (section)

[[File:DECTape unit for the DEC PDP-11.jpg|thumb|250x250px|A TU56 dual DECtape unit for a DEC PDP-11. Note the 6-armed "starfish" hubs holding circular white tape reels in place. The vertical aluminium block above each pair of tape reels holds the read/write heads.]]

'''DECtape''', originally called '''Microtape''', is a [[magnetic tape data storage]] medium used with many [[Digital Equipment Corporation]] [[computer]]s, including the [[PDP-6]], [[PDP-8]], [[LINC-8]], [[PDP-9]], [[PDP-10]], [[PDP-11]], [[PDP-12]], and the [[PDP-15]]. On DEC's 32-bit systems, [[OpenVMS|VAX/VMS]] support for it was implemented but did not become an official part of the product lineup.

DECtapes<ref name=DECbook>{{cite book|last1=Bell|first1=C. Gordon|last2=Mudge|first2=J. Craig|last3=McNamara|first3=John E.|title=COMPUTER ENGINEERING: A DEC View of Hardware Systems Design|url=https://archive.org/details/computerengineer00bell|url-access=registration|date=1978|publisher=Digital Press|location=Bedford, Mass.|isbn=9781483207674}}</ref> are {{convert|3/4|in|mm}} wide, and formatted into blocks of data that can each be read or written individually. Each tape stores 184K [[12-bit computing|12-bit]] PDP-8 words or 144K [[18-bit computing|18-bit]] words. [[Block (data storage)|Block size]] is 128 12-bit words (for the 12-bit machines), or 256 18-bit words for the other machines (16, 18, 32, or 36-bit systems).<ref>{{cite book|page=440|title=Open VMS Operating System Concepts|author=David Donald Miller|isbn=978-1555581572|year=1997}}</ref>

From a programming point of view,<ref name=DECbook/>{{rp|p.505}}<ref>A file system was developed for it, and is included in the [[PDP-6]] monitor.</ref> because the system is block-oriented and allows random seeking, DECtape behaves like a very slow disk drive.<ref>A PDP-6 using only DECtape, that formerly supported 4-6 timesharing users could, with a single disk drive, support up to 30 users - p.35, Volume 1, Number 1, The DEC Professional (magazine)</ref>