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Questions and Answers
What will be stored in the DX register after performing a division of unsigned numbers with the numerator in AX and the denominator in CL?
What will be stored in the DX register after performing a division of unsigned numbers with the numerator in AX and the denominator in CL?
In a doubleword/word division, where is the most significant word of the numerator stored?
In a doubleword/word division, where is the most significant word of the numerator stored?
What occurs if an overflow happens during signed arithmetic operations using the AL register?
What occurs if an overflow happens during signed arithmetic operations using the AL register?
What value allows the AL register to handle unsigned values during arithmetic operations?
What value allows the AL register to handle unsigned values during arithmetic operations?
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Which instruction logically shifts the operand to the right and fills the most significant bit with 0?
Which instruction logically shifts the operand to the right and fills the most significant bit with 0?
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What is the outcome of a logical shift left operation on a binary number?
What is the outcome of a logical shift left operation on a binary number?
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What maximum quotient can be obtained when performing a division with a byte dividend?
What maximum quotient can be obtained when performing a division with a byte dividend?
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When performing unsigned multiplication, what register will contain the lower half of the result when multiplying two words?
When performing unsigned multiplication, what register will contain the lower half of the result when multiplying two words?
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What condition leads to a Divide Error message during unsigned division?
What condition leads to a Divide Error message during unsigned division?
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In unsigned multiplication of a byte by a byte, where must one operand be located?
In unsigned multiplication of a byte by a byte, where must one operand be located?
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What is the result location for the operation of word times word multiplication?
What is the result location for the operation of word times word multiplication?
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What must be true of the AH register before performing a word-by-byte multiplication?
What must be true of the AH register before performing a word-by-byte multiplication?
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What will be the result locations after performing a byte over byte division?
What will be the result locations after performing a byte over byte division?
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What happens if the quotient from an unsigned division operation is too large for the assigned register?
What happens if the quotient from an unsigned division operation is too large for the assigned register?
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What values do AX and DX contain after performing a word times word multiplication?
What values do AX and DX contain after performing a word times word multiplication?
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What registers are essential for performing unsigned arithmetic operations in x86 architecture?
What registers are essential for performing unsigned arithmetic operations in x86 architecture?
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What happens to the carry flag (CF) after a subtraction operation?
What happens to the carry flag (CF) after a subtraction operation?
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What is the result of the operation 'SUB CH, 44H' when CH starts at 22H?
What is the result of the operation 'SUB CH, 44H' when CH starts at 22H?
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When executing an addition loop in assembly as shown, when should the loop terminate?
When executing an addition loop in assembly as shown, when should the loop terminate?
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Which operation effectively subtracts a memory location's content from a register in assembly language?
Which operation effectively subtracts a memory location's content from a register in assembly language?
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What is a consequence of the instruction 'ADC BX, 0' in the loop shown?
What is a consequence of the instruction 'ADC BX, 0' in the loop shown?
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What is a necessary step for initializing the Data Segment (DS) in the code segment shown?
What is a necessary step for initializing the Data Segment (DS) in the code segment shown?
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During multiword addition, what is the purpose of the instruction 'INC SI'?
During multiword addition, what is the purpose of the instruction 'INC SI'?
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What does the 'MOV AH, 4CH' instruction signify in the ending part of the code?
What does the 'MOV AH, 4CH' instruction signify in the ending part of the code?
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Study Notes
Division of Unsigned Numbers
- Division operations involving unsigned numbers in x86 processors utilize registers AX, AL, AH, and DX.
- Four distinct division cases exist: byte/byte, word/word, word/byte, doubleword/word.
- When dividing by zero or when the quotient exceeds the capacity of the assigned register, a "Divide Error" exception occurs, halting the program.
Division Cases
-
Word/Word:
- Numerator is in AX and DX (most significant word in DX, least significant in AX).
- Denominator can be in a register or memory location.
- After division, the quotient is stored in AX, and the remainder in DX.
- The maximum attainable quotient is FFFFH.
-
Byte/Byte:
- Numerator is in AL, and AH must be cleared (set to zero).
- Denominator cannot be immediate but can be in a register or memory.
- After division, the quotient is stored in AL, and the remainder in AH.
Multiplication of Unsigned Numbers
- Multiplication operations in x86 processors utilize registers AX, AL, AH, and DX.
- Three multiplication cases are possible: byte × byte, word × word, and byte × word.
Multiplication Cases
-
Byte × Byte:
- One operand must be in the AL register, and the second operand can be in a register or memory location.
- The result is stored in AX after the multiplication.
-
Word × Word:
- One operand must be in AX, and the second operand can be in a register or memory location.
- The result is a 32-bit value: AX holds the lower word, and DX holds the higher word.
-
Byte × Word:
- Similar to word × word but with the byte operand in AL and AH set to zero.
Signed Number Arithmetic Operations: Overflow Problem
- Signed number arithmetic can lead to overflow if the result goes beyond the capacity of the register.
- An 8-bit overflow occurs when the signed result is greater than 127 or less than -128.
- Despite overflow, the result is a correct 8-bit signed number.
Logic Instructions: Shift Right (SHR)
- Logical shift right shifts the operand right bit by bit, filling the MSB with 0.
- The LSB is moved to the carry flag (CF) during each shift.
Logic Instructions: Shift Left (SHL)
- Logical shift left is the opposite of SHR, shifting the operand left.
- The LSB is filled with 0, and the MSB is moved to CF, similar to SHR.
Subtraction
- The
SUBinstruction subtracts the second operand from the first operand and stores the difference in the first operand. - Examples:
-
SUB CL,BLCL = CL – BL -
SUB AX,SPAX = AX – SP -
SUB DI,TEMP[SI]DI = DI - TEMP[SI]
-
Flags After Subtraction
- The carry flag (C) and the auxiliary carry flag (A) hold borrow values instead of carries after subtraction.
- This reflects the potential for borrowing during a subtraction operation.
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Description
This quiz covers the division operations involving unsigned numbers in x86 processors, detailing four distinct cases. It explains how registers are utilized during these operations and addresses potential exceptions like 'Divide Error'. Test your knowledge on how division works in the x86 architecture!
