System console

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A system console was removed on older computers and the like. a. formed by a writing mechanism (modified typewriter); the keyboard is used for input, the printer function for output.

Friden Flexowriter

An example of these machines is the Friden Flexowriter.

“Another important feature was the ability to lead out keys that were pressed by cable or to control the type lever or the tape punch by cable. This led to the fact that the Flexowriter was used in most (American) computers in the 1950s and the first half of the 1960s as a peripheral device, especially as a console machine. This is also the case with the LGP 30 in the computer museum. It was not until the mid-1960s that they were supplanted by the Teletypes. "

LGP-30 at Manhattan College, 1965

In practical terms, this means that this was an input / output machine, 6, 7 or 8-bit coded (like the punched tape), which could also be connected to the computer without a punched tape (the parallel interface was available).

The optional paper tape readers and tape punches naturally increased the added value, as they represented additional input and output devices. The ASCII character set goes back to these machines.

Teletype

Telegraph , English teletypes (abbr .: TTY ), were often used; the serial interface with 40 mA allowed a cable length of several hundred meters with a pair of wires as well as a possible connection to the telex network. The disadvantage was the limited character set due to the 5-bit coding (no upper / lower case, no umlauts).

Command line interpreter

The interface between the machine (computer) and the user input / output device (keyboard, typewriter ) was formed by the software of the command line interpreter via the line that a typewriter begins after a carriage return and line feed. There the computer offers its services to a prompt using a character string . The user can enter his command there. This will be carried out, and when done the computer will offer its prompt again. Under certain circumstances, texts are output as a result of the command.

Shell

This line-oriented command line interpreter can be understood as the forerunner of a shell ; a shell is based on this mechanism. The tty devices to be found in the directory branch of a Unix machine under / dev / historically go back directly to the teletype.

MS-DOS

The sign of life of the command line interpreter COMMAND.COM is originally a "prompt" c> (output controllable via environment variable.) The entry of the command dirlists the contents of the current directory. Every MS-DOS version uses the key combination Ctrl + P to switch the standard output to the printer (it makes sense to use a line-based printer such as a matrix or type wheel printer). So work is also possible without a screen.

The device that is used is called “con” for console. This is a protected name under MS-DOS and all versions of Windows; an attempt to name a file or directory in con immediately leads to a protest from the operating system, "the specified device name is not allowed" (Windows 10).

A "copy Any.txt con" writes the content of the text file in the command line.

Individual evidence

  1. ↑ Friden Flexowriter Computer Museum of the Faculty of Computer Science at the University of Stuttgart

Web links