Allocation is the assignment of memory
to variables. When the compiler assigns one byte of memory to the
variable x, you
can say that both the byte and x
are allocated (the byte is allocated to x,
and x is allocated
one byte of memory).
Alignment refers to the position at which
a variable's share of memory begins. There are several types of
alignment.
Bit-aligned: If the byte that the
compiler allocates to x
can begin on a bit boundary.
1-byte-aligned: If the byte that the compiler allocates
must begin on a byte boundary.
2-byte-aligned: If the byte that the compiler allocates
must begin on a 2-byte boundary.
4-byte-aligned: If the byte that the compiler allocates
must begin on a 4-byte boundary.
8-byte-aligned: If the byte that the compiler allocates
must begin on a 8-byte boundary.
For the list of possible alignments, refer to "ALIGNMENT"
in the HP Pascal/iX Reference Manual or the
HP Pascal/HP-UX Reference Manual, depending
on your implementation.
The variables c
and d are allocated
one byte each, but c
is bit-aligned and d
is byte aligned.
A packing algorithm determines a variable's
allocation and alignment, and the allocation and alignment of its
elements or fields, if it has them. The HP Pascal packing algorithm
uses the following factors to allocate and align a particular variable:
Whether the variable (if it is an array, record,
or set) is unpacked, packed, or crunched.
When the compiler options TABLES or MAPINFO are ON, the program
listing contains packing information. Refer to the HP
Pascal/iX Reference Manual or the HP Pascal/HP-UX
Reference Manual, depending on your implementation,
for more information on compiler options.
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