37. Intel Reference Opcode Bytes, Cont.

• ib, iw, id - A 1-byte (ib), 2-byte (iw), or 4-byte (id) indicates presence of the immediate operand in the instruction.

• Typical order of opcode bytes is

  • opcode

  • Mod R/M byte (optional)

  • SIB scale-indexing byte (optional)

  • immediate operand.

• The opcode determines if the operand is a signed value.

• All words and doublewords are given with the low-order byte first (little endian).