It is primarily used to switch between the two text-entering modes on a personal computer (PC) or word processor:[1] The insert/overtype mode toggling is not global for the computer or even for a single application but rather local to the text input window in which the Insert key was pressed.
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.
[2] When keymapping using Octal code, the desired key may be set by sending \e\161 to perform the "insert" function.
[citation needed] Modern word processing applications operate in insert mode by default, but can still be switched to overtype mode by pressing the Insert key.
The Insert key, when pressed along with Control or Shift, can also be used to copy or paste in Microsoft Windows.