Omron NJ Series

A-93
Appendices
NJ-series CPU Unit Software User’s Manual (W501)
A-7 Variable Memory Allocation Methods
App
A-7-1 Variable Memory Allocation Rules
 Variables with Eight-byte Alignments (e.g., LWORD)
Eight bytes of memory are allocated for the eight-byte alignment.
The location of the first byte of data in memory is an integer multiple of eight bytes. Therefore, if a
variable with a two-byte alignment, such as WORD data, is inserted, six bytes of unused memory
will remain. If a variable with a four-byte alignment, such as DWORD data, is inserted, four bytes of
unused memory will remain.
Example: Consecutive variables in the following order: LWORD, WORD, and LWORD
Variable Table
Name
A
B
C
Data type
LWORD
WORD
LWORD
Variable A,
8 bytes
Variable B,
2 bytes
Variable C,
8 bytes
Bytes
Memory
First byte
First byte + 1
First byte + 2
First byte + 3
First byte + 4
First byte + 5
First byte + 6
First byte + 7
First byte + 8
First byte + 9
First byte + 10
First byte + 11
First byte + 12
First byte + 13
First byte + 14
First byte + 15
First byte + 16
First byte + 17
First byte + 18
First byte + 19
First byte + 20
First byte + 21
First byte + 22
First byte + 23
Not used.
First byte +
(integer multiple of 8)
First byte +
(integer multiple of 2)
First byte +
(integer multiple of 8)