Teletypewriter programming

The Teletypewriter (World Trade only) uses two different control characters for print formatting.

These control characters are as follows:

<   carriage return (X'22' in ITA2
    code or X'15' in EBCDIC)
 
=   line feed (X'28' in ITA2 code
     or X'25' in EBCDIC)

Use the character < first; otherwise following characters (data) can be printed while the type bar is moving to the left.

Message format

To begin a new message on a new line at the left margin, start the message text with X'1517' (EBCDIC). CICS® recognizes the X'17' and changes it to X'25' (X'17' is an IDLE character).

In the message body, to write several lines with a single transmission, the lines must be separated by X'1525', or if multiple blank lines are required, by X'152525...25'.

To allow input of the next message on a new line at the left margin, the preceding message must end with X'1517'. CICS recognizes X'15' and changes the character following it to X'25'.

If two or more successive output messages have “message begin” and “message end” which look the same, to make the “message end” of the preceding message distinguishable from the “message begin” of the next message, the next to last character of the “message end” must not be X'15'.

Message length

For messages for teletypewriter terminals do not exceed a length of about 3000 bytes or approximately 300 words.

Connection through z/OS Communications Server

Both the TWX Model 33/35 Common Carrier Teletypewriter Exchange and the WTTY Teletypewriter (World Trade only) can be connected to CICS through z/OS® Communications Server using NTO.

If a device is connected through z/OS Communications Server using NTO, the protocols used are the same as for the 3767 logical unit, and the application program can use these protocols (for example, HANDLE CONDITION SIGNAL). However, the data stream is not translated to a 3767 data stream but remains as that for a TWX/WTTY.