Seventh Edition Unix terminal interface

The three input modes for terminals in Seventh Edition Unix were:

line mode (also called "cooked" mode)

In line mode the line discipline performs all line editing functions and recognizes the "interrupt" and "quit" control characters and transforms them into signals sent to processes. Applications programs reading from the terminal receive entire lines, after line editing has been completed by the user pressing return.[2][7]

cbreak mode

cbreak mode is one of two character-at-a-time modes. (Stephen R. Bourne jokingly referred to it (Bourne 1983, p. 288) as a "half-cooked" and therefore "rare" mode.) The line discipline performs no line editing, and the control sequences for line editing functions are treated as normal character input. Applications programs reading from the terminal receive characters immediately, as soon as they are available in the input queue to be read. However, the "interrupt" and "quit" control characters, as well as modem flow control characters, are still handled specially and stripped from the input stream.[8][9]

raw mode

raw mode is the other of the two character-at-a-time modes. The line discipline performs no line editing, and the control sequences for both line editing functions and the various special characters ("interrupt", "quit", and flow control) are treated as normal character input. Applications programs reading from the terminal receive characters immediately, and receive the entire character stream unaltered, just as it came from the terminal device itself.[10][8][9]

In the POSIX terminal interface, these modes have been superseded by a system of just two input modes: canonical and non-canonical. The handling of signal-generating special characters in the POSIX terminal interface is independent of input mode, and is separately controllable.

In Seventh Edition Unix there was no terminal job control and a process group was considered to be not what it is considered to be nowadays.

Each process in the system had either a single controlling terminal, or no controlling terminal at all. A process inherits its controlling terminal from its parent. A controlling terminal was acquired when a process with no controlling terminal open()s a terminal device file that isn't already the controlling terminal for some other process. All of the processes that had the same controlling terminal were part of a single process group.[11]

The ioctl() operations were as follows:

One data structure used by the terminal system calls is the sgttyb structure, whose C programming language definition is as follows:[14]

struct sgttyb {
    char sg_ispeed ;    // Input speed
    char sg_ospeed ;    // Output speed
    char sg_erase ;     // Erase character
    char sg_kill ;      // Kill character
    char sg_flags ;     // Control flags
} ;

Unlike the POSIX terminal interface, the Seventh Edition Unix terminal interface recorded input and output baud rates directly in the data structure.[15]

The input and output speeds in the sg_ispeed and sg_ospeed fields were those of the DEC DH-11, and were the numbers 0 to 15, represented by the symbolic constants (in ascending order) B0, B50, B75, B110,B134, B150, B200, B300, B600, B1200, B1800, B2400, B4800, B9600, EXTA, and EXTB, where the baud rate was as in the name (with the last two being "external A" and "external B"). Setting a baud rate of zero forced the terminal driver to hang up a modem (if the terminal was a modem device).[14]

The sg_erase and sg_kill fields were simply the character values of the "erase" and "kill" characters, respectively, defaulting to the (ASCII) values for '#' and '@' respectively.[14]

The sg_flags field specified various input and output control flags, as in the following table.

One data structure used by the terminal system calls is the tchars structure, whose C programming language definition is as follows:[16]

struct tchars {
    char t_intrc ;      // Interrupt
    char t_quitc ;      // Quit
    char t_startc ;     // Start
    char t_stopc ;      // Stop
    char t_eofc ;       // End of File
    char t_brkc ;       // Break (alternative to hardwired LF character with same effect)
} ;

The values of these fields were the values of the various programmatically configurable special characters. A -1 value in any field disabled its recognition by the terminal driver.[16]