x86 Assembly Language Reference Manual

Move With Zero Extend (movzb)

movzb[wl]		r/m8, reg[16|32]
movzwl		r/m16, reg32

SignExtend(SRC) -> DEST


movzx reads the contents of the register or effective address as a word or byte. movzx then sign-extends the 16- or 32-bit value to the operand-size attribute of the instruction. The result is stored in the destination register by movzx.