HP 3000 Manuals

HP Pascal/iX Programmer's Guide

Chapter 5  Allocation and Alignment 

This chapter:

   *   Defines allocation, alignment, and packing algorithm.

   *   Shows how unpacked and packed variables are allocated and aligned.

   *   Tells how entire arrays and records are allocated and aligned
       (whether they are unpacked, packed, or crunched).

   *   Shows how array elements and record fields are allocated and
       aligned when they are unpacked, packed, and crunched.

   *   Explains how enumeration and subrange types are related and shows
       how they are allocated and aligned.

   *   Explains how files, sets, and strings are allocated and aligned.


NOTE  This chapter applies to the HP Pascal packing algorithm, which is
      the default.  On the MPE/iX operating system, the compiler option
      HP3000_16 specifies the Pascal/V packing algorithm instead.  For
      information on the HP3000_16 compiler option, refer to the HP 
      Pascal/iX Reference Manual.  For information on the Pascal/V
      packing algorithm, see Appendix A  in this manual.


In diagrams in this section, bold lines are byte boundaries and fine
lines are bit boundaries.  Unused bits and bytes are shaded.

Example 


            

Note that:

   *   Zero represents the Boolean value FALSE, and one represents TRUE.

   *   The leftmost bit represents the sign of a signed integer value.

Byte boundaries are broken where a variable crosses them.  Bit boundaries
are omitted where a variable crosses them.  A space that is allocated to
a variable contains the variable's name.  If the name does not fit the
space, it is printed outside, with an arrow pointing to the space.

Example 


            

The variables a and b occupy one bit each, c occupies six bits, d and e
occupy two bytes each, f occupies three bytes, and g occupies eight
bytes.

MPE/iX 5.0 Documentation