Правила форума
$A: Align Data SwitchLanguage:
Русский
English
$A: Align Data Switch
Switches between byte- and word-alignment of variables and typed constants.
Syntax: {$A+} or {$A-}
Default: {A+}
Type: Global
Menu Command: Options|Compiler|Align Data
Remarks
Word alignment has no effect on the 8088 CPU.
On all 80x86 CPUs, word alignment means faster execution.
- Word-sized items on even addresses are accessed in one memory cycle.
- Words on odd addresses are accessed in two memory cycles.
The $A+ State
In the $A+ state, all variables and typed constants larger than 1 byte are aligned on a machine-word boundary (an even-numbered address).
If required, unused bytes are inserted between variables to achieve word alignment.
$A+ does not affect byte-sized variables, fields of record structures, or elements of arrays.
A field in a record will align on a word boundary only if the total size of all fields before it is even.
For every element of an array to align on a word boundary, the size of the elements must be even.
The $A- State
In the $A- state, no alignment measures are taken.
Variables and typed constants are simply placed at the next available address, regardless of their size.
NOTE: Regardless of the state of $A, each global var and const declaration section always starts at a word boundary.
The compiler always keeps the stack pointer (SP) word-aligned by allocating an extra unused byte in a procedure's stack frame if required.
::
::
::
