Punched tape
Punched tape is an old-fashioned form of data storage, consisting of a long strip of paper in which holes are punched to store data.The earliest forms of punched tape come from weaving looms and embroidery, where cards with simple instructions about a machine's intended movements were first fed individually as instructions, then controlled by instruction cards, and later were fed as a string of connected cards.
This led to the concept of communicating analog 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, was eventually phased out, after many years of use, in the 1990s.
Punched tape was eventually also used as a way of storing messages for teletypewriters. The idea was to type in the message to the paper tape, and then send the message at "high speed" from the tape. The tape reader could "type" the message faster than a typical human operator, thus saving on phone bills.
When the first computers were being released many turned to the teletypewriter as a low-cost solution for printer output. This is why computers today still use ASCII, which was intended to be the standard character set for operating teletypewriters. As a side effect the punched tape readers became a popular medium for low cost storage, and it was common to find a selection of tapes containing useful program in most computer installations.
The little pieces of paper punched out of the tape are known as chad.
"Wikipedia" in punched tape code appears as the following (created by the BSD ppt program):
___________
| o o .ooo|
| oo o. o|
| oo o. oo|
| oo o. o|
| ooo . |
| oo .o o|
| oo .o |
| oo o. o|
| oo . o|
| o. o |
___________See also: punch card, chadless tape
The first use of paper tape predates computers, it was Thomas Edision and his Stock Ticker machines also his Repeating Telegraph. These were the forerunners of what became the computer punched paper tape.
There were two standards for computer tape. The Baudot which had 5 holes and the ASCII which had 8 holes. The image above shows an 8 hole tape. Teletypes were first used in conjunction with TWX Telex (also Telegrams), they were also adopted by Ham radio RTTY operators before finding their way into service as computer terminals.
Back in the late 1960s to early 1970s, the ASR33 was a very popular teletype. It had a built in paper tape reader and tape punch (8 hole ASCII). It could read/punch tape at the blinding speed of 10 characters per second. :-) The ASR33 tape reader was purely mechanical; 8 spring loaded fingers would be thrust into the tape (one character at a time), an amazing assortment of rods and levers would sense how high the finger rose, which told it if there was a hole in the tape at that position.
The ASR33 teletype that I worked with was hooked up to an HP minicomputer. Eventually the school also purchased a High Speed Photo Tape Reader, which consisted of 8 light sensors and could read a tape at the blinding speed of 50 inches per second (a similar photo reader also came with the DEC PDP 15).
The two biggest problems with paper tape is that (1) The ASR33 punch was not very reliable. After making a copy of a tape you would then have to compare hole by hole with the original tape (8k bytes checked by hand!). (2) The other big problem is rewinding the tape. You have this streamer that is perhaps 50 feet long and pretty fragile. You have to roll it back up before you can use it again, or store it. We had a modified electric eraser to assist with this. But great care was needed to avoid tearing the tape.
Repairing a mispunched or torn tape was a process of gluing a strip of punched tape over the damaged area.
- 12:27, 15 Jun 2004 (UTC)