ASCII

There is no formal structure controlling the use of the American National Standard Code for Information Interchange (ASCII) data stream to control printers attached to systems providing ASCII support. Control of page printers, like the IBM® 3812, is done by using page map primitives (PMPs), which are a set of commands or basic instruction set of these printers when attached in ASCII mode. ASCII data sent to a page printer is translated into PMPs. The page printer composes the page of data in its internal memory or page map. Two page orientations (portrait and landscape) as well as four print directions are supported. Complexity of the printed data is determined by the application print program, which can set the pels on explicitly in the page set, or implicitly, by instructing the printer to generate characters or vectors (lines). Fonts available for printing are stored on the printer's microcode or font diskette. Most page printers support macros, which are a saved list of PMP commands, avoiding the necessity for the application program to send a string of individual commands each time a particular printed function is required.

There are five basic categories of PMP commands:

Page commands

Set overall page parameters, such as size and orientation

Cursor commands

Move the cursor on the page map

Font commands

Manage fonts within the page printer

Generation commands

Create pels on the page map

Macro commands

Allow strings of other commands to be saved for later processing.

Printing capabilities and functions in ASCII attach mode are governed by individual application programs that are written to suit the capabilities of specific printers (or printers that provide an emulation of that printer). There is no architectural data stream standard to which ASCII printers can conform in the interests of uniformity. ASCII printing applications are therefore totally printer dependent.

On i5/OS, ASCII printing support is provided by translating iSeries™ server EBCDIC characters to the ASCII equivalents.