Insert key

Overview

On early text-based computing environments and terminals, when the cursor is in overtype mode, it was represented as a block that surrounded the entire letter to be overstruck; when in insert mode, the cursor consisted of the vertical bar that is highly common among modern applications, or a blinking underline under the position where a new character would be inserted.

On modern keyboards, the Insert key is only present on the control block between the typewriter keys and the numeric keypad. Originally an insert key was provided in the typewriter key block beside a delete key; both have been removed in favor of a double-sized 'backspace key'. The key was often maligned as unnecessary and more likely to be accidentally than intentionally activated.

When keymapping using Octal code, the desired key may be set by sending to perform the "insert" function.

History

Circa 1972, IBM Model B keyboards were equipped with an "INS MODE" key above the cursor arrow keys, next to "DEL". The Model B keyboards were used with 3270-series terminals that processed screen data locally before sending to the host.

HP 2640 series terminals, introduced in 1974, possessed an "Insert Char" mode-toggle button with a status light. It was positioned above the numeric keypad group, along with Delete Char, Insert Line, and Delete Line non-modal buttons.

The IBM 5100 portable (1975) showed Insert and Delete above the top-row cursor keys. The IBM 5150 PC (1981) featured Ins and Del on the and keys of its Model F keyboard.

Commodore included an INST|DEL key on its PET and C64 micro-computers from 1977 onwards.

Digital Equipment Corporation's VT220 terminal (1985) introduced an "INSERT HERE" key in the editing key group. It would send the escape sequence "CSI 2 ~" to the host. In return, a host application could send "CSI 4 h" or "CSI 4 l" to switch Insert/Replace Mode (IRM) on the terminal.

XTerm, a terminal emulator for the X Window System, sends "CSI 2 ~" in DEC mode, "CSI 2 z" in Sun mode, "ESC Q" in HP mode, and "CSI L" in SCO mode.

Use in applications

Modern word processing applications operate in insert mode by default, but can still be switched to overtype mode by pressing the Insert key. Some applications indicate overtype mode with a letter-width cursor box, as opposed to the standard narrow cursor; however, others use the narrow cursor for both modes, and indicate overtype with an "OVR" indicator in the status bar.

The Insert key, when pressed along with Control or Shift keys, can also be used to copy or paste in Microsoft Windows. This behavior comes from the Common User Access standard.

Screen readers use the insert key for hotkeys for reading text, speaking formatting information, or opening the screen reader's configuration menu or window.

References

References

1. "Definition of overtype mode".
2. (1 February 2012). "Five Modest Proposals for Improving the Computer Keyboard". [[Slate Magazine]].
3. Shark, Admiral. (2024-02-06). "Differentiating IBM 3101, 3270 & 5250 terminal keyboards".
4. Loewen, Mike. "HP2647A-37L".
5. (1978). "2645A Display Station User's Manual".
6. [[c:File:Snow_Survey65_(38349185954).jpg. Snow Survey 65]], photograph (1975), United States Department of Agriculture, Natural Resources Conservation Service, Montana. Depicts a man working at a 2640A terminal, the edit group of keys are present on the top-right of the keyboard.
7. Dunfield, Dave. "IBM 5100".
8. Dunfield, Dave. "PC compatibles".
9. Dunfield, Dave. "Commodore PET".
10. Doctorow, Cory. (2020-02-06). "Original prototype PET, secret hardware archive, Computer History Museum, Mountain View, California, USA".
11. Originally at top-right of the numeric keypad, then relocated to top-right of the main key group.
12. Williams, Paul Flo. "VT100.net: Digital VT220 Programmer Reference Manual".
13. Williams, Paul Flo. "VT100.net: Digital VT220 Programmer Reference Manual".
14. Moy, Edward. "XTerm Control Sequences".