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OPL stores its variables’ data in memory in a specific format; this topic details the sequences of memory bytes used for different data types.
Usually you would find out the byte address with the ADDR function. For example, if var% has the value 7, PEEKW(ADDR(var%)) returns 7.
See also the PEEK and POKE commands and ADDR. See also 32-bit addressing.
MARM, WINS
Under both the WINS and MARM platforms, the byte with the lower address is the least significant — MARM and WINS are both little-endian.
Future EPOC devices may use a different machine word format.
Integers are stored in two bytes. The first byte is the least significant byte, for example:
1 0 = 1
0 1 = 256
ADDR returns the address of the first (least significant) byte.
Long integers are stored in four bytes, the least significant first and the most significant last, for example:
0 0 1 0 = 65536
ADDR returns the address of the first (least significant) byte.
Strings are stored with one character per byte, with a leading byte containing the string length, e.g.:
3 65 66 67 = "ABC"
Each letter is stored as its character code - for example, A as 65.
For example, if var$="ABC", PEEK$(ADDR(var$)) will return the string ABC. ADDR returns the address of the length byte.
Floating-point numbers are stored in IEEE format across eight bytes. PEEKF automatically reads all eight bytes and returns the number as a floating-point. For example if var=1.3 then PEEKF(ADDR(var)) returns 1.3.
You can use ADDR to find the address of the first element in an array, for example ADDR(x%()), you can also specify individual elements of the array, for example ADDR(x%(2)).
The length of the array is stored in the two bytes immediately before the first element, and can be examined with PEEKW:
proc demopeek:
local ar%(42)
print peekw(addr(ar%()) - 2)
get
endp
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