Common questions

What does CDQ mean in assembly?

What does CDQ mean in assembly?

Description. The CDQ (Convert Doubleword to Quadword) instruction extends the sign bit of EAX into the EDX register.

What is CLTD Assembly?

Description. cltd converts the signed long in EAX to a signed double long in EDX:EAX by extending the most-significant bit (sign bit) of EAX into all bits of EDX.

What is CWD assembly language?

This instruction (Convert signed Word to signed Doubleword) copies the sign bit of a word in AX to all the bits of DX. DX is then the sign extension of AX. This instruction must be done before a signed word in AX can be divided by another signed word with the IDIV instruction.

What is CDQE?

The CDQE instruction sign-extends a DWORD (32-bit value) in the EAX register to a QWORD (64-bit value) in the RAX register. The MOVZX instruction zero-extends the source to the destination. In this case, it sign-extends the BYTE loaded from memory at [rbp-528+rax] to the DWORD destination register, EAX .

What does CBW do in assembly?

The cbw instruction sign-extends a byte into a word. In this case, it’ll take the sign bit of AL (which happens to be 1) and copy it into every bit of AH . This means that the two’s-complement value of AX will be the same, but the binary representation will be different.

How does a Div assembly work?

div executes unsigned division. div divides a 16-, 32-, or 64-bit register value (dividend) by a register or memory byte, word, or long (divisor). The quotient is stored in the AL, AX, or EAX register respectively. The remainder is stored in AH, Dx, or EDX.

What does LEA instruction do?

The lea instruction places the address specified by its first operand into the register specified by its second operand. Note, the contents of the memory location are not loaded, only the effective address is computed and placed into the register.

How does CDQ work?

The CDQ instruction copies the sign (bit 31) of the value in the EAX register into every bit position in the EDX register. The CQO instruction can be used to produce a double quadword dividend from a quadword before a quadword division. The CWD and CDQ mnemonics reference the same opcode.

What is difference between div and IDIV?

The DIV instruction divides unsigned numbers, and IDIV divides signed numbers. Both return a quotient and a remainder. The dividend is the number to be divided, and the divisor is the number to divide by. The quotient is the result.

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