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AIX Version 4.3 Assembler Language Reference

stb (Store Byte) Instruction


Stores a byte of data from a general-purpose register into a specified location in memory.


stb RS,D(RA)


The stb instruction stores bits 24-31 of general-purpose register (GPR) RS into a byte of storage addressed by the effective address (EA).

If GPR RA is not 0, the EA is the sum of the contents of GPR RA and D, a 16-bit signed two's complement integer sign-extended to 32 bits. If GPR RA is 0, then the EA is D.

The stb instruction has one syntax form and does not affect the Fixed-Point Exception Register or Condition Register Field 0.


RS Specifies source general-purpose register of stored data.
D Specifies a 16-bit, signed two's complement integer sign-extended to 32 bits for EA calculation.
RA Specifies source general-purpose register for EA calculation.


The following code stores bits 24-31 of GPR 6 into a location in memory:

.csect data[rw]
buffer: .long 0
# Assume GPR 4 contains address of csect data[rw].
# Assume GPR 6 contains 0x0000 0060.
.csect text[pr]
stb 6,buffer(4)
# 0x60 is now stored at the address of buffer.

Related Information

Fixed-Point Processor.

Fixed-Point Load and Store Instructions.

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