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STOSW Store String Word Flags: not altered
Logic: (ES:DI) . AX
if DF = 0
DI . DI + 2
else
DI . DI - 2
STOSW copies the value in AX into the location pointed to by ES:DI. DI
is then incremented (if the direction flag is cleared) or decremented
(if the direction flag is set), in preparation for storing AX in the
next location.
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Operands Clocks Transfers Bytes Example
- 15 1 1 STOSW
(repeat) 9 + 14/rep 1/rep 1 REP STOSW
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When used in conjunction with the REP prefixes, the Store String
instructions are useful for initializing a block of memory. For
example, the following code would initialize the 100-byte memory block
at BUFFER to 0:
MOV AX,0 ;The value to initialize BUFFER to
LEA DI,BUFFER ;Starting location of BUFFER
MOV CX,50 ;Size of BUFFER, in words
CLD ;Let's move in forward direction
REP STOSW ;Compare this line to example for STOS