Punched tape or perforated paper tape is a form of data storage,
consisting of a long strip of paper in which holes are punched to
store data. Now effectively obsolete, it was widely used during much
of the twentieth century for teleprinter communication, for input to
computers of the 1950s and 1960s, and later as a storage medium for
minicomputers and CNC machine tools.
2 Tape formats
2.2 Chadless tape
3.3 Data transfer for ROM and
3.4 Cash registers
3.5 Newspaper industry
3.6 Automated machinery
Punched tape in art
7 Current use
8 See also
10 External links
A paper tape, constructed from punched cards, in use in a Jacquard
loom. The large holes on each edge are sprocket holes, used to pull
the paper tape through the loom.
Paper tapes constructed from punched cards were widely used throughout
the 19th century for controlling looms. Perforated paper tapes were
first used by
Basile Bouchon in 1725 to control looms. However, the
paper tapes were expensive to create, fragile, and difficult to
repair. By 1801,
Joseph Marie Jacquard
Joseph Marie Jacquard had developed machines to
create paper tapes by tying punched cards in a sequence. The resulting
paper tape, also called a "chain of cards", was stronger and simpler
both to create and to repair. (See Jacquard loom).
This led to the concept of communicating data not as a stream of
individual cards, but one "continuous card", or a tape. Many
professional embroidery operations still refer to those individuals
who create the designs and machine patterns as "punchers", even though
punched cards and paper tape were eventually phased out, after many
years of use, in the 1990s.
In 1846, Alexander Bain used punched tape to send telegrams.
In 1842, a French patent by Claude Seytre described a piano playing
device that read data from perforated paper rolls.
Charles Wheatstone used paper tape for the preparation,
storage and transmission of data in telegraphy.
Tolbert Lanston invented the Monotype System, which
consisted of a keyboard (typesetting machine) and a composition
caster. The tape, punched with the keyboard, was later read by the
caster, which produced lead type according to the combinations of
holes in 0, one or more of 31 positions. The tape reader used
compressed air, which passed through the holes and was directed into
certain mechanisms of the caster. The system went into commercial use
in 1897 and was in production well into the 1970s, undergoing several
changes along the way.
A 24-channel program tape for the Harvard Mark I
Data were represented by the presence or absence of a hole at a
particular location. Tapes originally had five rows of holes for data.
Later tapes had six, seven and eight rows. An early electro-mechanical
calculating machine, the Automatic Sequence Controlled Calculator or
Harvard Mark I, used paper tape with twenty-four rows. A row of
smaller sprocket holes that were always punched served to feed the
tape, originally using a wheel with radial teeth called a sprocket
wheel. Later optical readers used the sprocket holes to generate
timing pulses. The sprocket holes are slightly to one side, making it
clear which way to orient the tape in the reader and dividing the tape
into unequal sides. The bits on the narrower side of the tape are
generally the least significant bits, when the code is represented as
numbers in a digital system.
Text was encoded in several ways. The earliest standard character
encoding was Baudot, which dates back to the nineteenth century and
had five holes. The
Baudot code was never used in teleprinters.
Instead, modifications such as the Murray code (which added carriage
return and line feed), Western Union code, International Telegraph
Alphabet No. 2 (ITA 2), and American Teletypewriter code (USTTY), were
used. Other standards, such as
Flexowriter, had six holes. In the early 1960s, the American Standards
Association led a project to develop a universal code for data
processing, which became known as ASCII. This seven-level code was
adopted by some teleprinter users, including AT&T (Teletype).
Others, such as Telex, stayed with the earlier codes.
Tape for punching was 0.00394 inches (0.1 mm) thick. The two most
common widths were 11/16 inch (17.46 mm) for five bit codes, and
1 inch (25.4 mm) for tapes with six or more bits. Hole spacing
was 0.1 inch (2.54 mm) in both directions. Data holes were 0.072
inches (1.83 mm) in diameter; feed holes were 0.046 inches
Most tape-punching equipment used solid punches to create holes in the
tape. This process created "chad", or small circular pieces of paper.
Managing the disposal of chad was an annoying and complex problem, as
the tiny paper pieces had a tendency to escape and interfere with the
other electromechanical parts of the teleprinter equipment.
Chadless 5-level Baudot paper tape circa ~1975–1980 punched at
A variation on the tape punch was a device called a Chadless Printing
Reperforator. This machine would punch a received teleprinter signal
into tape and print the message on it at the same time, using a
printing mechanism similar to that of an ordinary page printer. The
tape punch, rather than punching out the usual round holes, would
instead punch little U-shaped cuts in the paper, so that no chad would
be produced; the "hole" was still filled with a little paper
trap-door. By not fully punching out the hole, the printing on the
paper remained intact and legible. This enabled operators to read the
tape without having to decipher the holes, which would facilitate
relaying the message on to another station in the network. Also, there
was no "chad box" to empty from time to time. A disadvantage to this
mechanism was that chadless tape, once punched, did not roll up well,
because the protruding flaps of paper would catch on the next layer of
tape, so it could not be rolled up tightly. Another disadvantage, as
seen over time, was that there was no reliable way to read chadless
tape by optical means employed by later high-speed readers. However,
the mechanical tape readers used in most standard-speed equipment had
no problem with chadless tape, because it sensed the holes by means of
blunt spring-loaded sensing pins, which easily pushed the paper flaps
out of the way.
The word , and a CR/LF as 7-bit ASCII, without a parity
bit, least significant bit on the right - e.g. "W" is 1010111
Paper tape relay operation at US FAA's Honolulu flight service station
Punched tape was used as a way of storing messages for
teletypewriters. Operators typed in the message to the paper tape, and
then sent the message at the maximum line speed from the tape. This
permitted the operator to prepare the message "off-line" at the
operator's best typing speed, and permitted the operator to correct
any error prior to transmission. An experienced operator could prepare
a message at 135 words per minute (WPM) or more for short periods.
The line typically operated at 75WPM, but it operated continuously. By
preparing the tape "off-line" and then sending the message with a tape
reader, the line could operate continuously rather than depending on
continuous "on-line" typing by a single operator. Typically, a single
75WPM line supported three or more teletype operators working offline.
Tapes punched at the receiving end could be used to relay messages to
another station. Large store and forward networks were developed using
Paper tape could be read into computers at up to 1000 characters per
second. The Danish company
Regnecentralen developed a paper tape
reader called RC 2000 that could read 2000 characters per second. It
was introduced in 1963. Later they increased the speed further, up to
2500 cps. As early as World War II, the Heath Robinson tape reader,
used by Allied codebreakers, was capable of 2000 cps while
Colossus could run at 5000 cps using an optical tape reader designed
by Dr Arnold Lynch.
Software on fanfold paper tape for the
Data General Nova
Data General Nova minicomputer
When the first minicomputers were being released, most manufacturers
turned to the existing mass-produced
ASCII teleprinters (primarily the
Teletype Model 33, capable of ten
ASCII characters per second
throughput) as a low-cost solution for keyboard input and printer
output. The commonly specified Model 33 ASR included a paper tape
punch/reader, where ASR stands for "Automatic Send/Receive" as opposed
to the punchless/readerless KSR – Keyboard Send/Receive and RO –
Receive Only models. As a side effect, punched tape became a popular
medium for low cost minicomputer data and program storage, and it was
common to find a selection of tapes containing useful programs in most
minicomputer installations. Faster optical readers were also common.
Binary data transfer to or from these minicomputers was often
accomplished using a doubly encoded technique to compensate for the
relatively high error rate of punches / readers. The low-level
encoding was typically ASCII, further encoded and framed in various
schemes such as
Intel Hex – in which a binary value of "01011010"
would be represented by the
ASCII characters "5A". Framing, addressing
and checksum (primarily in
ASCII hex characters) information provided
error detection capabilities. Efficiencies of such an encoding scheme
are on the order of 35–40% (e.g. 36% from 44 8-bit
being needed to represent sixteen bytes of binary data per frame).
Data transfer for ROM and
In the 1970s through the early 1980s, paper tape was commonly used to
transfer binary data for incorporation in either mask-programmable
read-only memory (ROM) chips or their erasable counterparts –
EPROMs. A significant variety of encoding formats were developed for
use in computer and ROM/
EPROM data transfer. Encoding formats
commonly used were primarily driven by those formats that EPROM
programming devices supported and included various
ASCII hex variants
as well as a number of computer-proprietary formats.
A much more primitive as well as a much longer high-level encoding
scheme was also used – BNPF (Begin-Negative-Positive-Finish). In
BNPF encoding, a single byte (8 bits) would be represented by a highly
redundant character framing sequence starting with a single
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 sequences were separated by one or more
whitespace characters, therefore using at least eleven ASCII
characters for each byte stored (9% efficiency). The
ASCII "N" and "P"
characters differ in four bit positions, providing excellent
protection from single punch errors. Alternative schemes were also
available where "H" and "L" or "0" and "1" were also available to
represent data bits, but in both of these encoding schemes, the two
ASCII characters differ in only one bit position,
providing very poor single punch error detection.
National Cash Register
National Cash Register or NCR (Dayton Ohio) made cash registers around
1970 that would punch paper tape. The tape could then be read into a
computer and not only could sales information be summarized, billings
could be done on charge transactions.
Punched paper tape was used by the newspaper industry until the
mid-1970s or later. Newspapers were typically set in hot lead by
devices such as a linotype. With the wire services coming into a
device that would punch paper tape, rather than the linotype operator
having to retype all the incoming wire stories, the paper tape could
be put into a paper tape reader on the linotype and it would create
the lead slugs without the operator re-typing the stories. This also
allowed newspapers to use devices, such as the Friden Flexowriter, to
convert typing to lead type via tape. Even after the demise of the
Linotype/hot lead, many early "offset" devices had paper tape readers
on them to produce the news-story copy.
Paper tape reader on a computer numerical control (CNC) machine
In the 1970s, computer-aided manufacturing equipment often used paper
Paper tape was a very important storage medium for
computer-controlled wire-wrap machines, for example. A paper tape
reader was smaller and much less expensive than hollerith card or
magnetic tape readers. Premium black waxed and lubricated long-fiber
papers, and Mylar film tape were invented so that production tapes for
these machines would last longer.
Vernam ciphers were invented in 1917 to encrypt teleprinter
communications using a key stored on paper tape. During the last third
of the 20th century, the
National Security Agency
National Security Agency used punched paper
tape to distribute cryptographic keys. The eight-level paper tapes
were distributed under strict accounting controls and read by a fill
device, such as the hand held KOI-18, that was temporarily connected
to each security device that needed new keys. NSA has been trying to
replace this method with a more secure electronic key management
system (EKMS), but as of 2016, paper tape is apparently still being
employed. The paper tape canister is a tamper resistant container
that contains features to prevent undetected alteration of the
Fanfold paper tape
The three biggest problems with paper tape were:
Reliability. It was common practice to follow each mechanical copying
of a tape with a manual hole-by-hole comparison.
Rewinding the tape was difficult and prone to problems. Great care was
needed to avoid tearing the tape. Some systems used
fanfold paper tape rather than rolled paper tape. In these systems, no
rewinding was necessary nor were any fancy supply reel, takeup reel,
or tension arm mechanisms required; the tape merely fed from the
supply tank through the reader to the takeup tank, refolding itself
back into exactly the same form as when it was fed into the reader.
Low information density. Datasets much larger than a few dozen
kilobytes are impractical to handle in paper tape format.
Punched tape does have some useful properties:
Longevity. Although many magnetic tapes have deteriorated over time to
the point that the data on them has been irretrievably lost, punched
tape can be read many decades later, if acid-free paper or Mylar film
is used. Some paper can degrade rapidly.
Human accessibility. The hole patterns can be decoded visually if
necessary, and torn tape can be repaired (using special all-hole
pattern tape splices). Editing text on a punched tape was achieved by
literally cutting and pasting the tape with scissors, glue, or by
taping over a section to cover all holes and making new holes using a
manual hole punch.
Magnetic field immunity. In a machine shop full of powerful electric
motors, the numerical control programs need to survive the magnetic
fields generated by those motors.
Ease of destruction. In the case of cryptographic keys, the inherent
flammability (sometimes enhanced by using flash paper) of paper tape
was an asset. Once the key had been loaded into the device, the paper
tape could simply be burned, preventing the key from falling into
Punched tape in art
A computing or telecommunications professional depicted in the
Monument to the Conquerors of Space
Monument to the Conquerors of Space in Moscow (1964) holds what
appears to be a punched tape with three rows of rectangular holes.
Use of punched tape today is very rare. It may still be used in older
military systems and by some hobbyists. In CNC
machining applications, what few existing installations remained in
grandfathered use are now quickly disappearing as the
advantages for new orders of old part designs are being superseded by
natural economic evolution. However, some modern CNC
systems still measure the size of stored CNC programs in feet or
meters, corresponding to the equivalent length if punched on paper
Zygalski sheets – a system used to decrypt messages enciphered on
German Enigma machines
^ Maxfield, Clive (13 October 2011). "How it was:
Paper tapes and
punched cards". EE Times.
^ Dalakov, Georgi, History of computers: The MARK computers of Howard
Aiken, retrieved 2011-01-12
^ Proesch, Roland (2009). Technical Handbook for Radio Monitoring HF:
Edition 2009. Books on Demand. ISBN 3837045730.
^ Hult, Ture (1963), "Presentation of a new high speed paper tape
reader", BIT Numerical Mathematics, 3 (2): 93–96,
File Formats" (PDF). Data I/O Corporation. Retrieved
^ Tale of the Tape, NSA/CSS, May 3, 2016, Accessed June 16, 2014
^ Sinha, N.K. (30 June 1986). Microprocessor-Based Control Systems.
Springer. p. 264. ISBN 978-90-277-2287-4.
Paper tape is well
suited to a machine shop environment whereas magnetic tape may be
accidentally erased or contaminated by foreign substances.
... Other disadvantages of paper tape are as
^ Smid, Peter (2010). CNC Control Setup for Milling and Turning:
Mastering CNC Control Systems. Industrial Press. p. 20.
Wikimedia Commons has media related to Punched tapes.
"ECMA standard for Data Interchange on Punched Tape". European
Computer Manufacturers Association. November 1965. ECMA-10.
A song mentioning paper tape
Various punched media
Flexowriter combination typewriter, paper tape punch, and paper
tape reader, designed by IBM during the 1940s and bought out by Friden
in the late 1950s (Retrieved April 10, 2007)
Detailed description of two paper tape code systems,
Baudot code and
the system used by the
Paper data storage media
Writing on papyrus (c. 3000 BCE)
Paper (105 CE)
Railroad/Transit Punch Photograph (1880s)
Punched card (1890)
Edge-notched card (1896)
Optical mark recognition
Optical character recognition (1929)