TerminalMode

TerminalMode describes a configuration state of a terminal interface that governs how input and output are processed by a program interacting with a terminal. It is a conceptual setting used by many libraries and applications to control user input, editing, and display behavior, and is commonly exposed as an enumerated type or a set of flags in code.

Two widely discussed modes are canonical (also called cooked) mode and raw mode. In canonical mode, input is line buffered: keystrokes are edited and accumulated into complete lines before being delivered to the program. In raw mode, input is delivered immediately with minimal processing, allowing the program to interpret each keystroke. Additional controls typically include echo (whether typed characters are shown) and signal handling (whether characters such as Ctrl-C generate interrupts).

On POSIX systems, terminal behavior is manipulated via termios; a program retrieves current attributes with tcgetattr, adjusts flags such as ICANON, ECHO, and ISIG, and reapplies them with tcsetattr. On Windows, console input and output modes are controlled by console mode flags such as ENABLE_LINE_INPUT, ENABLE_ECHO_INPUT, and ENABLE_PROCESSED_INPUT.

TerminalMode is central to interactive shells, read–eval–print loops, text editors that run in a terminal, and games or tools that require precise keystroke handling. It enables responsive interfaces and full control over how user input is interpreted and displayed, including secure handling of input in password prompts.

When designing with TerminalMode, developers should consider portability, user experience, and security. Differences between platforms and libraries require abstraction layers or conditional code to ensure consistent behavior across environments.