Introduction

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 “MPE/iX Dependencies ” 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.

Figure 5-1 Allocation and Alignment Example 1

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.

Figure 5-2 Allocation and Alignment Example 2

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.

Introduction

Technical documentation

» Table of Contents

» Glossary

» Index