A set of utility functions are provided to set up the xterm. A function, xtermRead, is provided to read from the xterm and a function, xtermWrite to write to the xterm. Both these functions are blocking on the operating system. The write function should always be able to write with minimal delay. However the read function must only be called when the SIGIO signal handler has determined input is available, in order to avoid blocking the SystemC simulation.

There is some internal state to hold the pseudo-TTY file descriptors and the process ID of the xterm (so it can be killed by the destructor). It is the slave file descriptor that is used for both input and output.