Editing Punched tape (section)

=== Minicomputers ===
[[file:Harvard Mark I program tape.agr.jpg|thumb|upright|A 24-channel program tape for the [[Harvard Mark I]] ({{c.|1944}})]]
When the first [[minicomputer]]s were being released, most manufacturers turned to the existing mass-produced [[ASCII]] [[teleprinter]]s (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|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 [[minicomputer]]s was often accomplished using a doubly encoded technique to compensate for the relatively high error rate of punches and 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 helped with error detection. Efficiencies of such an encoding scheme are on the order of 35–40% (e.g., 36% from 44 8-bit ASCII characters being needed to represent sixteen [[byte]]s of binary data per frame).