Double Column Output Routines

Abstract

Two double column output routines will be presented in this chapter beginning with an explanation of their basic principles. There are essentially two different ways to handle double column output:

• 1 Treat left- and right-hand columns as two separate logical pages. When the output routine is called, then box register 255 either contains a “left column logical page” (in that case box register 255 is simply saved in another box register with no output to the dvi file) or a “right column logical page” (in this case the previously saved left column and the right column contained in box register 255 are now written together out to the dvi file). See 37.1 on this page for such an output routine.

• 2 Generate left and right columns as a single column of double page length and then split this double long column into two columns using \vsplit. In other words, the splitting of left and right columns is not done “automatically” by the page breaking algorithm as was the case in the previous approach, but the double long column is split into two columns by the output routine. A double column output routine using this approach can be found in 37.2, p. 166. The version of this output routine discussed at the given reference offers an additional feature in that it allows switching back and forth between single and double column output.