## ALP Programming Guide and Reference

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### Description

CWD and CDQ double the size of the source operand. The CWD instruction copies the sign (bit 15) of the word in the AX register into every bit position in the DX register. The CDQ instruction copies the sing (bit 31) of the doubleword in the EAX register into every bit position in the EDX register. The CWD instruction can be used to produce a doubleword dividend from a word before a word division, and the CDQ instruction can be used to produce a quadword dividend from a doubleword before doubleword division. The CWD and CDQ instructions are different mnemonics for the same opcode. Which one gets run is determined by whether it is in a 16- or 32-bit segment and the presence of any operand-size override prefixes.