NOTE

Use of communications features. This program allows the user to attach a line and enter a conversational mode with a device connected to the line.

EQU ESC TO CHAR(27) ; * ESC used for control sequence

*

PROMPT '-'

MYLINE = SYSTEM(101); * Get current LINKED line # LOOP

   PRINT "ENTER LINE NUMBER OR 'END'":

      ; *Prompt for target line

   INPUT LINE

UNTIL LINE = "END" DO

   LOOP

      EXECUTE "LINE-ATT ":LINE RETURNING

            ERR ; *Attempt to attach line

   UNTIL ERR = "8013" DO REPEAT ; * Errmsg 8013 =

      'LINE ATTACHED'

REPEAT

*

IF LINE = "END" THEN STOP

*

ESCAPE = 0;  EXIT = 0 ; * Initialize flags

ECHO OFF ; * Full duplex:  device will echo input

*

LOOP

   GET BYTE FROM MYLINE THEN ; * Get single char from terminal

      IF ESCAPE THEN ; * Is this second char of ESC seq?

         IF BYTE = "X" THEN EXIT = 1 ;* exit from conversation

         IF BYTE = ESC THEN

            SEND BYTE:  TO LINE ELSE EXIT = 1

         END   

      END ELSE

         IF BYTE = ESC THEN

             ESCAPE = 1 ELSE ; *If char is ESC set flag

         END ELSE

            SEND BYTE:  TO LINE ELSE EXIT = 1

               ; * Send char without CR LF

         END

      END

END ELSE ; * If no terminal input then

   GET BYTE FROM LINE THEN CRT BYTE:

      ;* get char from target line

END ; * if any, send to terminal

UNTIL EXIT DO REPEAT

*

ECHO ON ; * Turn echo back on

EXECUTE "LINE-DET ":LINE ; * Detach the line

PRINT "CONVERSATION ENDED"