CICS 3270 printer options

PRINT option and print control bit

Writing to a 3270 display or printer updates the device buffer. On a display, the results are reflected immediately on the screen, which is a driven from the buffer. For a printer, however, there might be no visible effect, because printing does not occur until you turn on the appropriate bit in the write control character (WCC).

The WCC is part of the 3270 data stream; see The output datastream. For BMS, you turn on the print bit by specifying the PRINT option on a SEND MAP, SEND TEXT, or SEND CONTROL command, or in the map used with SEND MAP. If you are using terminal control SEND commands, you must turn on the print bit with the CTLCHAR option.

A terminal write occurs on every terminal control SEND, and on every SEND MAP, SEND TEXT, or SEND CONTROL unless you are using the ACCUM or PAGING options. ACCUM delays writing until a page is full or the logical message is ended. When you use ACCUM, you should use the same print options on every SEND command for the same page. PAGING defers the terminal writes to another task, but they are generated in the same way as without PAGING.

The fact that printing does not occur until the print bit is on allows you to build the print buffer in stages with multiple writes and to change data or attribute bytes already in the buffer. That is, you can use the hardware to achieve some of the effects that you get with the ACCUM option of BMS. The NLEOM option affects this ability, however; see the discussion at NLEOM option.

ERASE option

Like the 3270 display buffer, the 3270 printer buffer is cleared only when you use a write command that erases. You do this by specifying the ERASE option, both for BMS and terminal control SEND commands.

If the printer has the alternate screen size feature, the buffer size is set at the time of the erase, as it is for a display. Consequently, the first terminal write in a transaction should include erasing, to set the buffer to the size required for the transaction and to clear any buffer contents left over from a previous transaction.

BMS and terminal control SEND commands are listed in CICS command summary.

Line width options: L40, L64, L80, and HONEOM

In addition to the print bit, the write control character contains a pair of bits that govern line length on printing.

If you are using terminal control commands, you use the CTLCHAR option to set these bits. For BMS, the default is the one produced by the HONEOM option, which stands for honor end-of-message. With this setting, the printer formats according to the buffer control and print format orders only, stopping printing at the first EM (end-of-message) character in the buffer. Only if you attempt to print beyond the maximum width for the device (the platen width) does the printer move to a new line on its own.

However, you also can specify that the line length is fixed at 40, 64, or 80 characters (options L40, L64 and L80). If you do, the printer ignores certain print format orders, moves to a new line when it reaches the specified line size, and prints the entire buffer. The print format orders that are ignored are NL (new line), CR (carriage return), and EM (end-of-message). Instead they are printed, as graphics.

If you use L40, L64, or L80 under BMS, only use the value that corresponds to the page width in your terminal definition (see Determining the characteristics of a CICS printer). The reason is that BMS calculates buffer addresses based on the page size, and these addresses are wrong if you use a different page width.

NLEOM option

BMS ordinarily uses buffer control orders, rather than print format orders, to format for a 3270 printer, whether you are using SEND TEXT or SEND MAP. However, you can tell BMS to use print format orders only, by specifying the NLEOM option.

You might want to do this to maintain compatibility with an SCS printer (print format orders are compatible with the corresponding SCS control characters). The following operational differences might cause you to choose or avoid NLEOM.

Blank lines

The 3270 printer suppresses null lines during printing. That is, a line that has no data fields and appears blank on the display screen is omitted when the same map is sent to a printer. Under BMS, you can force the printed form to look exactly like the displayed form by placing at least one field on every line of the screen; use a field containing a single blank for lines that would otherwise be empty. Specifying NLEOM also has this effect, because BMS uses a new line character for every line, whether or not there is any data on it.

Multiple SEND commands

With NLEOM, data from successive writes is stacked in the buffer, since it does not contain positioning information. However, BMS adds an EM (end-of-message) character at the end of data on each SEND with NLEOM, unless you are using the ACCUM option. When printing occurs, the first EM character stops the printing, so that only the data from the first SEND with NLEOM (and any unerased data up to that point in the buffer) gets printed. The net effect is that you cannot print a buffer filled with multiple SEND commands with NLEOM unless you use the ACCUM option.

Page width

BMS always builds a page of output at a time, using an internal buffer whose size is the number of character positions on the page. See Determining the characteristics of a CICS printer for a discussion of how BMS determines the page size. If you are using buffer control orders to format, the terminal definition must specify a page width of 40, 64, 80 or the maximum for the device (the platen size); otherwise, your output might not be formatted correctly. If you are using NLEOM, on the other hand, the terminal definition may specify any page width, up to the platen size.

Total page size

If you are using buffer control orders, the product of the number of lines and the page width must not exceed the buffer size, because the buffer is used as an image of the page. Unused positions to the right on each line are represented by null characters. If you use NLEOM, however, BMS does not restrict page size to the buffer capacity. BMS builds the page according to the page size defined for the terminal and then compresses the stream using new-line characters where possible. If the resulting stream exceeds the buffer capacity, BMS uses multiple writes to the terminal to send it.

FORMFEED option

The FORMFEED option causes BMS to put a form feed print format order (X'0C') at the beginning of the buffer, if the printer is defined as capable of advancing to the top of the form (with the FORMFEED option in the associated TYPETERM definition). CICS ignores a form feed request for a printer defined without this feature.

If you issue a SEND MAP using a map that uses position (1,1) of the screen, you overwrite the order and lose the form feed. This occurs whether you are using NLEOM or not.

If you use FORMFEED and ERASE together on a SEND CONTROL command, the results depend on whether NLEOM is present. Without NLEOM, SEND CONTROL FORMFEED ERASE sends the form feed character followed by an entire page of null lines. The printer suppresses these null lines, replacing them with a single blank line. With NLEOM, the same command sends the form feed character followed by one new line character for each line on the page, so that the effect is a full blank page, just as it is on a non-3270 printer.

PRINTERCOMP option

When you SEND TEXT to a printer, there is one additional option that affects page size. This is the PRINTERCOMP option, which is specified in the PROFILE associated with the transaction you are executing, rather than on individual SEND TEXT commands. In the default profile that CICS provides, the PRINTERCOMP value is NO.

Under PRINTERCOMP(NO), BMS produces printed output consistent with what it would send to a 3270 display. For the display, BMS precedes the text from each SEND TEXT command with an attribute byte, and it also starts each line with an attribute byte. These attribute bytes take space on the screen, and therefore BMS replaces them with blanks for printers if PRINTERCOMP is NO. If PRINTERCOMP is YES, BMS suppresses these blanks, allowing you to use the full width of the printer and every position of the buffer. New line characters that you embed in the text are still honored with PRINTERCOMP(YES), as they are with PRINTERCOMP(NO).

You should use PRINTERCOMP(NO) if you can, for compatibility with display devices and to ensure consistent results if the application uses different printer types, even though it reduces the usable line width by one position.