Specifications

B-5Calculatin Page Width Using Printer Colon File Escape Sequence
numbered steps correspond to the numbers on the left side of the columns in the figure, and
provide a step–by–step description of the evaluation of the printer colon file escape
sequences defining page width, in characters, for this particular queue (asc), colon file, and
command line.
Figure 7. Calculation of Page Width
1. %Cw – Pushes a 0 onto the stack because the w flag was not used on the command
line.
2. %I_w – Calls for the evaluation of _w.
3. %G_z – Pushes a 1 onto the stack.
4. %{1} – Pushes a 1 onto the stack.
5. %& – Pops the top two values (two 1 s) off the stack, performs a bitwise AND on the two
values, and pushes the resultant 1 onto the stack.
6. %t – Pops the 1 off the stack and, because it is a TRUE (non–zero) value, calls for the
evaluation of %GwK.
7. %GwK – Calls for the evaluation of wK.
8. %G_Q – Calls for the evaluation of _Q.
9. %GwQ – Calls for the evaluation of wQ.
10.%GWu – Calls for the evaluation of Wu.
11.%CO – Pushes a 0 onto the stack because the O flag was not used on the command
line.
12.%t – Pops the 0 off the stack and, because it is a FALSE (zero) value, calls for the
evaluation of %G_u. The stack labeled Wu is now empty.
13.%G_u – Pushes a 1 onto the stack.
14.%d – Pops the 1 off the stack and returns it, in ASCII format, to the in–progress
calculation of wQ.
15.%{0} – Pushes a 0 onto the stack.
16.%= – Pops the 0 and 1 off the stack, compares them for equality, and pushes the
resultant 0 onto the stack.