Programs obtain data values or programming instructions {input, computer} by opening and reading files. Input devices include magnetic tape, magnetic disk, magnetic drum, card reader, microfilm, microfiche, keytape from typewriter to tape, paper-tape reader, mark-sense reader, optical character recognition {optical character recognition} (OCR), cathode ray terminal, data cells, magnetic card, diskette, floppy disk, and flash memory card.
Programs display, print, send data to other devices, or make data-value or programming-parameter files {output, computer}. Output devices include de-collator, burster, folder, line printer, laser printer, card puncher, paper tape puncher, key-to-disc, and key-to-drum.
File transfer protocol {file transfer protocol} (FTP) allows public file access via anonymous log on. There is a user account for anonymous logons (GUEST by default) and a default home directory.
CPUs can connect {channel} to one input or output device {fixed channel} or switch from one input or output device to another {floating channel}.
Input-output lines {line, input and output} {input line} {output line} connect CPU and device. Direct lines {bit stream} can connect one input or output device to CPU. Leased telephone lines and modems connect one input or output device to CPU. Multiple lines connect to switching network, which connects to CPU. CPU lines {multi-drop line} can have several modems, so CPU polls and selects data. CPU lines {line concentrator} can receive direct and telephone lines, poll them, and send bit-stream packets to CPU.
Computer devices {adapter} can make bits into line characters.
Computer devices {data communications controller} {datacom} can control data input and output from different terminals.
types
Datacoms {uniplexor} {single line control} (SLC) can take bits from one line and pass characters to CPU. Datacoms {multiplexor} {multi-line control} (MLC) can take bits from many lines, sort bits by logic, and send characters to CPU. Datacoms {front-end processor} (FEP) can take bits from several lines, assemble them into words, and send words to CPU. Datacoms {data communications processor} can take bits from one line, assemble them into words, add message header, queue messages, and send them to memory or input-output processor.
Devices {modem}| {data set} can convert digital bits to analog data, or vice versa, or alter line bit streams.
Devices {sort-merge} can manipulate input and output forms.
3-Computer Science-Hardware-Input-Output
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Date Modified: 2022.0225