Computer Architecture: Flag Register Quiz
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Questions and Answers

Which flag indicates that an arithmetic operation has resulted in an overflow?

  • Overflow Flag (OF) (correct)
  • Carry Flag (CF)
  • Sign Flag (SF)
  • Zero Flag (ZF)

    • What happens to the Zero Flag (ZF) after performing an ADD operation that results in a non-zero value?

  • ZF remains unchanged
  • ZF is reset to the default state
  • ZF is set to 0 (correct)
  • ZF is set to 1

    • Which flag is affected when adding two numbers if a carry occurs from the third to the fourth bit?

  • Sign Flag (SF)
  • Parity Flag (PF)
  • Carry Flag (CF)
  • Auxiliary Carry Flag (AF) (correct)

    • Which operation does NOT change any flags?

    <p>MOV</p> Signup and view all the answers

    After performing the operation ADD BH, 2FH with BH initialized to 38H, what will be the result of the Parity Flag (PF)?

    <p>PF = 0</p> Signup and view all the answers

    Which of the following flags indicates a negative result after an arithmetic operation?

    <p>Sign Flag (SF)</p> Signup and view all the answers

    Which instruction group affects all flags except for the Carry Flag (CF)?

    <p>INC and DEC</p> Signup and view all the answers

    If an operation results in a high-order bit overflow, which flag will be set?

    <p>Overflow Flag (OF)</p> Signup and view all the answers

    What is the primary purpose of flags in a flag register?

    <p>To control program flow by making decisions</p> Signup and view all the answers

    Which bits in the flag register are primarily used for control flags?

    <p>Bits 8, 9, and 10</p> Signup and view all the answers

    Which of the following is NOT one of the six status flags?

    <p>Trap Flag (TF)</p> Signup and view all the answers

    How many bits of the flag register are used for decision making?

    <p>9 bits</p> Signup and view all the answers

    What type of flag is the Overflow Flag (OF)?

    <p>A status flag</p> Signup and view all the answers

    Which of the following is the primary function of the Direction Flag (DF)?

    <p>Control the direction of the operand for data movement</p> Signup and view all the answers

    The Sign Flag (SF) reflects the result of which type of operation?

    <p>Comparison and arithmetic operations</p> Signup and view all the answers

    Which bits in the flag register are allocated as 'Undefined'?

    <p>Bits 1, 3, 4, 6, 12, 14</p> Signup and view all the answers

    What is the value of the Carry Flag (CF) after the addition of 0AAAAH and 5556H?

    <p>1</p> Signup and view all the answers

    Which of the following flags is set due to a carry from d3 to d4 in the provided addition?

    <p>Auxiliary Flag (AF)</p> Signup and view all the answers

    What must be true for a conditional jump instruction to be executed?

    <p>Certain specified conditions must be true.</p> Signup and view all the answers

    In assembly language, what is the primary purpose of loop instructions?

    <p>To repeat sections of code.</p> Signup and view all the answers

    What is the result of the Zero Flag (ZF) after performing the addition operation specified?

    <p>1</p> Signup and view all the answers

    Which instruction type allows for transfer to another point in the program without conditions?

    <p>Unconditional Jump</p> Signup and view all the answers

    Which of the following describes the syntax of a conditional jump instruction?

    <p>Jxxx destination_label</p> Signup and view all the answers

    The Parity Flag (PF) is set based on which condition in the addition operation detailed?

    <p>An even number of 1’s is present in the result.</p> Signup and view all the answers

    Which addressing mode involves the use of constant values as operands?

    <p>Immediate Addressing Mode</p> Signup and view all the answers

    What is a characteristic of Register Addressing Mode?

    <p>It uses registers to hold data without accessing memory.</p> Signup and view all the answers

    In which addressing mode does the address of the data come immediately after the instruction?

    <p>Direct Addressing Mode</p> Signup and view all the answers

    Which of the following addressing modes is NOT one of the seven distinct modes provided by the 8086 microprocessor?

    <p>Dynamic Addressing Mode</p> Signup and view all the answers

    Which statement about the source and destination registers in Register Addressing Mode is correct?

    <p>They must match in size to avoid errors.</p> Signup and view all the answers

    Which addressing modes are considered the most common for data access in the 8086 microprocessor?

    <p>Direct and Indirect</p> Signup and view all the answers

    What is the defining feature of Immediate Addressing Mode?

    <p>Constant values are used directly in the instructions.</p> Signup and view all the answers

    What value will the carry flag (CF) be set to after the operation ADD AL, DH where AL is initially 9CH and DH is 64H?

    <p>1</p> Signup and view all the answers

    Which addressing mode is characterized by accessing memory using a base address plus an offset?

    <p>Based Relative Mode</p> Signup and view all the answers

    Which flags are set or cleared in the flag register after executing ADD AX, DX where AX is 34F5H and DX is 95EBH?

    <p>PF = 0, AF = 1, ZF = 0</p> Signup and view all the answers

    What is the result of the operation ADD AL, DH where AL is 9CH and DH is 64H in hexadecimal?

    <p>A0H</p> Signup and view all the answers

    When executing the instruction MOV BX, 34F5H, what is the hexadecimal representation held in BX?

    <p>34F5H</p> Signup and view all the answers

    What is the state of the Overflow Flag (OF) after the operation ADD AX, DX with AX as 34F5H and DX as 95EBH?

    <p>0</p> Signup and view all the answers

    Given the operation ADD AL, DH resulting in a zero result, what is true about the Zero Flag (ZF)?

    <p>ZF would be set to 1</p> Signup and view all the answers

    What would be the effect on the Auxiliary Flag (AF) during the addition of 9CH and 64H?

    <p>Set to 1</p> Signup and view all the answers

    After executing the ADD instruction that results in a negative number, which flag will indicate this state in the flag register?

    <p>SF</p> Signup and view all the answers

    Study Notes

    Flag Register

    • The flag register is a 16-bit register, and only 9 bits are used for decision-making
    • Six of the flags are called status flags:
      • Carry Flag (CF)
      • Parity Flag (PF)
      • Auxiliary Carry Flag (AF)
      • Zero Flag (ZF)
      • Sign Flag (SF)
      • Overflow Flag (OF)
    • Three of the flags are control flags, enabling or disabling processor operations:
      • Direction Flag (DF)
      • Interrupt Enable Flag (IF)
      • Trap Flag (TF)

    Status Flags

    • Carry Flag (CF): Set to 1 if there is a carry out or borrow in, otherwise cleared.
    • Parity Flag (PF): Set to 1 if the number of 1's in the result is even, otherwise cleared.
    • Auxiliary Carry Flag (AF): Set to 1 if there is a carry from d3 to d4, otherwise cleared. Used in BCD operations.
    • Zero Flag (ZF): Set to 1 if the result of an arithmetic or logical operation is zero, otherwise cleared.
    • Sign Flag (SF): Set to 1 if the MSB of the result is 1 (negative), otherwise cleared.
    • Overflow Flag (OF): Set to 1 if a signed operation overflows, otherwise cleared. Only used for signed arithmetic.

    How Instructions Affect Flags

    • MOV and XCHG: No flags are changed
    • ADD and SUB: All flags affected
    • INC and DEC: All flags except CF affected
    • NEG: All flags affected

    Unconditional Jump: JMP Instruction

    • Unconditionally transfers control to another point in the program.
    • Syntax: JMP destination

    Conditional Jumps

    • Transfers control only if certain conditions are met.
    • Category: Single Flag jumps, Register jumps
    • Syntax: Jxxx destination_label

    Addressing Modes

    • Register Addressing Mode: Uses registers to hold the data, no memory access is required. Ex: MOV BX, DX
    • Immediate Addressing Mode: Source operand is a constant. Ex: MOV AX, 2550H
    • Direct Addressing Mode: Directly specifies the memory address of the data. Ex: MOV BX, [0010H]

    Direct Addressing Mode

    • Data is stored in memory locations.
    • The address of the data in memory comes immediately after the instruction.
    • Direct addressing mode is a common way to access data in the data segment.

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    Lecture 03 Memory Addressing Modes & Program Flow Control PDF

    Description

    Test your knowledge on the flag register in computer architecture. This quiz covers both status and control flags, their functions, and implications in decision-making processes within processors. Challenge yourself to understand how these bits influence operations!

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