OS_In, read (wait for) character from standard input

RST 20H, DEFB $2A

IN:

     -

     Fc = 0
     A = character read from standard input

     Fc = 1
     A = error code:
          RC_SUSP ($69), process suspended or machine revived
          RC_DRAW ($66), process suspended and screen corrupted
          RC_QUIT ($67), kill request
          RC_ESC ($01), escape condition detected

     ..BCDEHL/IXIY same
     AF....../.... different

This call wait until the result is available.

Crashes OZ while in a popdown with safe workspace more than 32 bytes, and the popdown gets pre-empted (RC_QUIT).

GN_Sip, system input line routine
OS_Pur, purge keyboard buffer
OS_Tin, read character from standard input, with timeout
OS_Xin, examine input