Punched tape: Difference between revisions

{{Short description|FormData ofstorage data storagedevice}}

[[file:PaperTapes-5and8Hole.jpg|thumb|Five- and eight-hole wide punched paper tape]]

'''Punched tape''' or '''perforated paper tape''' is a form of [[data storage]] device|data storage]] that consists of a long strip of paper inthrough which small holes are punched. It was developed from and was subsequently used alongside [[punched card]]s, differingthe difference inbeing that the tape is continuous.

Punched cards, and chains of punched cards, were used for control of looms[[loom]]s in the 18th century. Use for telegraphy systems started in 1842. Punched tapetapes waswere used throughout the 19th and for much of the 20th centuries for programmable looms, [[teleprinter]] communication, for input to computers of the 1950s and 1960s, and later as a storage medium for [[minicomputer]]s and [[Numerical control|CNC machine tool]]s. During the Second World War, high-speed punched tape systems using optical readout methods were used in code breaking systems. Punched tape was used to transmit data for manufacture of [[read-only memory]] chips.

In 1846, [[Alexander Bain (inventor)|Alexander Bain]] used punched tape to send [[telegram]]s. This technology was adopted by [[Charles Wheatstone]] in 1857 for the [[Wheatstone system]] used for the automated preparation, storage and transmission of data in telegraphy.<ref name="Maxfield_2011"/><ref>{{cite web | url name= https://distantwriting.co.uk/cookewheatstone.html | title = 3. Cooke and Wheatstone | last = "Roberts | first = Steven | website = Distant Writing: A History of the Telegraph Companies in Britain between 1838 and 1868 }}<"/ref>

In the 21st century, use of punched tape would be very rare, possibly inis obsolete militaryexcept systems or by someamong [[Retrocomputing|hobbyists]]. In [[Numerical control|computer numerical control]] (CNC) machining applications, though paper tape ishas uncommon,been butsuperseded by [[Semiconductor memory|digital memory]], some modern systems still measure the size of stored CNC programs in feet or meters, corresponding to the equivalent length if the data were actually punched on paper tape.<ref name="Smid_2010"/>

Data was represented by the presence or absence of a hole at a particular location. Tapes originally had five rows of holes for data across the width of the tape. Later tapes had six, seven, or eightmore rows. A 1944 electro-mechanical programmable calculating machine, the Automatic Sequence Controlled Calculator or [[Harvard Mark I]], used paper tape with 24 rows.,<ref name="Dalakov"/> The [[IBM SSEC|IBM Selective Sequence Electronic Calculator (SSEC)]] used paper tape with 74 rows.<ref>{{cite web| url = https://www.columbia.edu/cu/computinghistory/ssec-tape.html| title = SSEC Tape| last = da Cruz| first = Frank| date = April 2021| website = Columbia University Computing History| access-date = 25 May 2024}}</ref> Australia's 1951 electronic computer, [[CSIRAC]], used {{convert|3|in|mm|adj=on}} wide [[paper tape]] with twelve rows.<ref name="CSIRAC_2010"/>

In the 1970s, [[computer-aided manufacturing]] equipment often used paper tape. A paper tape reader was smaller and less expensive than [[hollerithHollerith card]] or [[magnetic tape]] readers, and the medium was reasonably reliable in a manufacturing environment. Paper tape was an important storage medium for computer-controlled [[wire-wrap]] machines, for example.

{{anchor|BNPF|BPNF|BHLF|B10F}}A much more primitive as well as a much longer high-level encoding scheme was also used, [[BNPF]] (Begin-Negative-Positive-Finish),<ref name="Intel_1974"/><ref name="Feichtinger_1987"/> also written as [[BPNF]] (Begin-Positive-Negative-Finish).<ref name="Intel_1977"/> In BNPF encoding, a single [[byte]] (8 bits) would be represented by a highly redundant character framing sequence starting with a single uppercase ASCII "B", eight ASCII characters where a "0" would be represented by a "N" and a "1" would be represented by a "P", followed by an ending ASCII "F".<ref name="Intel_1974"/><ref name="Intel_1977"/><ref name="Feichtinger_1987"/> These ten-character ASCII sequences were separated by one or more [[whitespace character]]s, therefore using at least eleven ASCII characters for each byte stored (9% efficiency). The ASCII "N" and "P" characters differed in four bit positions, providing excellent protection from single punch errors. Alternative schemes named BHLF (Begin-High-Low-Finish) and B10F (Begin-One-Zero-Finish) were also available where either "L" and "H" or "0" and "1" were also available to represent data bits,<ref name="GP_1984"/> but in both of these encoding schemes, the two data-bearing ASCII characters differ in only one bit position, providing very poor single punch error detection.

<ref name="Sinha_1986">{{cite book |author-first=N.Naresh K. |author-last=Sinha |title=Microprocessor-Based Control Systems |url=https://books.google.com/books?id=JgalRre0L8wC&pg=PA264 |date=30 June 1986 |publisher=Springer |isbn = 978-90-277-2287-4 |pages=264}}</ref>