9.12 CARRIAGE CONTROL

Vertical spacing is defined for a page of printed output by a Forms Control Buffer (FCB). A default FCB is associated with each form used for printed output; the defaults for Computer Center-supplied forms are established by the Center. A default FCB for each user-supplied form is established by the user when the form is registered.

A data set can be printed using either machine carriage control or ASA carriage control. Machine carriage control uses unprintable hexadecimal characters in column 1 of each record of the data set to control vertical spacing. As its name implies, machine carriage control is the carriage control that printers actually use to control vertical spacing when printing on a form. ASA carriage control uses printable characters in column 1 of each record of the data set to control vertical spacing; the ASA carriage control characters are translated into machine carriage control by the JES2 component of the operating system before the output is printed.

A record format (RECFM) ending in A indicates that the data set has ASA carriage control; one ending in M indicates machine carriage control. If an invalid character appears in the carriage control column, the results are unpredictable. If a data set does not contain carriage control, the RECFM should not include A or M (e.g., RECFM=FB), and column one of each record of the data set will treated as text.

When carriage control characters (either ASA or machine) are used for controlling output spacing, two types of positioning can be used: line-oriented and channel-oriented. Line-oriented positioning specifies the number of lines to "move the carriage" before or after the line is printed. The line-oriented carriage control characters are defined by the system, and are NOT specified within the FCB.

In channel-oriented positioning, the FCB relates channel codes (1-9, A-C) to specific lines on a form. Channel-oriented carriage control characters initiate a vertical "skip" down the lines of a page. To terminate the skip, a channel code corresponding to the carriage control character must be coded in the FCB. This channel code marks the line on the form where the skip will terminate. For example, if the FCB defines channel 8 to relate to line 55 on a form, and a carriage control character of 8 is encountered in the output, the form will automatically advance to line 55 before printing resumes. As another example, if the FCB defines channel 11 ("B") to be associated with lines 14 and 45 on a form, and a carriage control character of B is encountered in the output, the form will automatically advance to either line 14 or 45, whichever is encountered first.

The JES2 component of the operating system requires that Channel 1 be defined in all FCBs. JES2 "skips to Channel 1" prior to printing the Header and Trailer pages on the output. For output other than labels, Channel 1 is always print line 4 for 6 lines-per-inch density, line 5 for 8 lpi, and line 6 for 10 lpi. Other channels may be set at vertical positions above Channel 1 for impact printing, but may not be set above Channel 1 in FCBs intended for the laser printers. For labels, Channel 1 should be defined near the top of the label and Channel 10 should be defined as the last print line before the perforation on a page of labels.

Line-Oriented Carriage Control Characters

Channel Oriented Carriage Control Characters