Understanding CPU Flags in Computer Architecture
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Questions and Answers

What is the purpose of the OFFSET assembler directive?

  • To load the offset value of a variable into a register (correct)
  • To access elements of an array using an index
  • To add a constant to the contents of a register to get the final address
  • To pass a parameter to a procedure

    • What is the purpose of the indexed addressing mode?

  • To access elements of an array using an index (correct)
  • To add a constant to the contents of a register to get the final address
  • To pass a parameter to a procedure
  • To load the offset value of a variable into a register

    • What is the difference between using OFFSET and the lea instruction to load the address of a variable into a register?

  • OFFSET loads the actual address, while lea loads the effective address
  • OFFSET is more efficient than lea for loading variable addresses
  • OFFSET has run-time overhead, while lea has assembly-time overhead
  • OFFSET can only be used for variables, while lea can be used for more complex addressing modes (correct)

    • When would you need to use the lea instruction instead of the OFFSET directive?

    <p>When the needed data is available at run time only</p> Signup and view all the answers

    What is the purpose of the displacement addressing mode?

    <p>To add a constant to the contents of a register to get the final address</p> Signup and view all the answers

    Which addressing mode is used to access array elements using an index stored in a register?

    <p>Indexed addressing mode</p> Signup and view all the answers

    What does the CS (Code Segment) register store?

    <p>Starting address of the code segment in memory</p> Signup and view all the answers

    How are 40-bit numbers stored after multiplication?

    <p>Most significant 40 bits in AC, least significant in MQ</p> Signup and view all the answers

    What does SS (Stack Segment) register point to?

    <p>Starting address of the stack</p> Signup and view all the answers

    Which register holds the starting address of an extra data segment?

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

    What is the default size of a quad word?

    <p>8 bytes</p> Signup and view all the answers

    Which combination represents a default 32-bit segment and offset?

    <p>32-bit segment and offset</p> Signup and view all the answers

    What does the Trap Flag (T) do when set to 1?

    <p>Enables single-step mode for processor operation</p> Signup and view all the answers

    When the Direction Flag (D) is set to 1, what happens to the registers during string instructions?

    <p>Registers are automatically decremented</p> Signup and view all the answers

    What does the Overflow Flag (O) indicate after a signed arithmetic operation?

    <p>Overflow of a high-order bit</p> Signup and view all the answers

    What is the purpose of the I/O Privilege Level field (IOPL)?

    <p>Defines privilege level of current process</p> Signup and view all the answers

    What activates the Alignment Check flag bit (AC)?

    <p>Word or doubleword addressed on a non-boundary</p> Signup and view all the answers

    What does the Nested Task (NT) flag control?

    <p>Linking current process to the next process</p> Signup and view all the answers

    What is the purpose of the jump operation mentioned in the text?

    <p>To specify the address of the next instruction in the program</p> Signup and view all the answers

    How many classes of instructions are mentioned in the text?

    <p>5</p> Signup and view all the answers

    What is the size of an instruction in the 4-address instruction format?

    <p>13 bytes</p> Signup and view all the answers

    What is the maximum amount of memory that can be accessed by the 4-address instructions?

    <p>16 MB</p> Signup and view all the answers

    What type of machine is based on an accumulator register?

    <p>Accumulator based machine</p> Signup and view all the answers

    Which machine type works on the principle of Last In First Out (LIFO)?

    <p>Stacked based machine</p> Signup and view all the answers

    What is a characteristic of an Accumulator based machine?

    <p>Second term of an operation is fetched from memory</p> Signup and view all the answers

    Which machine type requires less memory access?

    <p>Accumulator based machine</p> Signup and view all the answers

    In a General purpose registers machine, how are addresses designed?

    <p>With minimal bits for few registers</p> Signup and view all the answers

    What is the main feature of a Stacked based machine?

    <p>Operates on the LIFO principle</p> Signup and view all the answers

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