Machine Instructions and Addressing Modes Quiz
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Questions and Answers

What does the base register in displacement addressing mode hold?

  • The actual value of the operand
  • The size of the operand
  • The final address of the operand
  • The beginning address of the operand (correct)

    • What is the principal advantage of using immediate addressing mode?

  • Simple to implement
  • Large address space
  • Flexibility in addressing
  • No memory reference needed (correct)

    • Which addressing mode has limited applicability as a principal disadvantage?

  • Stack Addressing (correct)
  • Indirect Addressing
  • Displacement Addressing
  • Register Indirect Addressing

    • Which addressing modes are suitable for program relocation at runtime?

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

    What defines absolute addressing mode?

    <p>The operand's address is explicitly stated in the instruction.</p> Signup and view all the answers

    What do three-address instructions allow for in terms of operations?

    <p>They perform operations that can utilize three different operands.</p> Signup and view all the answers

    Which type of instruction organization is characterized by having an implicit accumulator?

    <p>Single accumulator organization</p> Signup and view all the answers

    In a general register organization, how many accumulators can be utilized?

    <p>Two or three</p> Signup and view all the answers

    What is a primary benefit of different addressing modes in programming?

    <p>They enhance data indexing and program relocation.</p> Signup and view all the answers

    Which of the following is NOT a type of instruction mentioned in the content?

    <p>Four-address instructions</p> Signup and view all the answers

    What operation does the instruction 'SUB Y, A, B' represent?

    <p>Y = Y - A - B</p> Signup and view all the answers

    What is a unique feature of stack organization compared to other CPU organizations?

    <p>It uses implicit operations for PUSH and POP.</p> Signup and view all the answers

    Which instructions are primarily used in a one-address instruction organization?

    <p>LOAD, ADD, STORE operations</p> Signup and view all the answers

    What does the instruction 'DIV Y, T' accomplish?

    <p>Y is divided by T, storing the result in Y.</p> Signup and view all the answers

    What role does the Control Unit (CU) play in CPU organization?

    <p>It manages instruction execution and directing operations.</p> Signup and view all the answers

    What does the instruction specifying 'immediate' addressing mode mean?

    <p>The operand is provided within the instruction.</p> Signup and view all the answers

    Which addressing mode utilizes the contents of the Program Counter to determine the effective address?

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

    In which addressing mode is the actual address of the operand specified by the instruction?

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

    What is the primary characteristic of 'indirect' addressing mode?

    <p>The instruction specifies a memory address where the actual address of the operand is located.</p> Signup and view all the answers

    What does the base register addressing mode utilize to obtain the effective address?

    <p>Contents of the base register and address part of the instruction</p> Signup and view all the answers

    In index addressing mode, what is the purpose of the index register?

    <p>To store offset values that are added to the base address</p> Signup and view all the answers

    What is the main role of the offset in relative addressing mode?

    <p>It is added to the Program Counter to find the effective address.</p> Signup and view all the answers

    Implied addressing mode does what?

    <p>Does not specify the operand or its address.</p> Signup and view all the answers

    Which type of instruction is used primarily for transferring data between memory and registers?

    <p>Data Transfer Instructions</p> Signup and view all the answers

    What type of instruction would you use to perform arithmetic operations like addition or multiplication?

    <p>Manipulation Instructions</p> Signup and view all the answers

    Which addressing mode uses a combination of a base register and an index for computing the effective address?

    <p>Base with Index and Displacement</p> Signup and view all the answers

    What is the purpose of the 'Call' instruction in a subroutine?

    <p>To initiate a transfer of control to another instruction</p> Signup and view all the answers

    Which of the following best describes RISC architecture?

    <p>Focuses on a small set of instructions and limited addressing modes</p> Signup and view all the answers

    What does the program counter (PC) do during an interrupt?

    <p>Holds the address of a return instruction</p> Signup and view all the answers

    Which instruction is NOT a control instruction?

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

    In x86 architecture, what does the displacement addressing mode use for address calculation?

    <p>Sum of a base address and a specified offset</p> Signup and view all the answers

    Which instruction is responsible for clearing the contents of a register?

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

    Which instruction manipulates data in a logical manner?

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

    Which of the following instructions is categorized under data transfer?

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

    What does the term 'single cycle instruction execution' refer to in RISC architecture?

    <p>All instructions are executed in one clock cycle</p> Signup and view all the answers

    How does the 'Push' instruction affect the stack pointer?

    <p>Decrements the stack pointer</p> Signup and view all the answers

    Which type of instructions primarily handle decision making in a program?

    <p>Control Instructions</p> Signup and view all the answers

    Study Notes

    Machine Instructions and Addressing Modes

    • Machine instructions consist of a set of bits which include opcode and operands, specifying operations like ADD, SUB, and INR.
    • Types of CPU organizations include single accumulator, general register, and stack organization.
    • Three-address instructions allow for explicit operands, e.g., SUB Y, A, B performs Y = A - B.
    • Two-address instructions involve one instruction or accumulator, e.g., ADD T, C updates T with T + C.
    • One-address instructions only specify one operand, e.g., LOAD D, which loads D into the accumulator (AC).

    Advantages of Addressing Modes

    • Addressing modes enhance programming capabilities by offering pointers for data access, loop control, indexing, and program relocation.
    • They reduce the bit count needed in instruction addressing fields.

    Basic Addressing Modes

    • Immediate: Operand specified directly in the instruction, leading to no memory reference but limited operand magnitude.
    • Direct: Uses the effective address (EA) directly from the instruction, simple but has limited address space.
    • Indirect: EA is determined from a memory address specified in the instruction, allows large address spaces but requires multiple memory references.
    • Register: Operand is in a specified register, resulting in no memory reference but limited addressability.
    • Register Indirect: Operand's address is kept in a register, providing flexibility with added memory reference complexity.
    • Displacement: Adds offset to a register to find the operand, which offers flexibility but also adds complexity.
    • Stack: Operands are accessed from the top of the stack with no memory references; however, its applicability is limited.

    Advanced Addressing Techniques

    • Auto Increment/Decrement: Automatically adjusts the address used after each operation, suitable for loops.
    • Base Register Addressing: Similar to indexed addressing but uses a base register, offering flexibility in memory location access.

    Types of Instructions

    • Data Transfer Instructions: Include operations like LOAD, STORE, PUSH, and POP.
    • Data Manipulation Instructions: Spanning arithmetic (ADD, SUBTRACT, MPY, DIV), logical operations, and shift operations.
    • Control Instructions: Include branching (IF, WHILE, FOR), jumps, and function calls.

    Addressing for Program Relocation

    • Suitable addressing modes for program relocation include Relative and Base Addressing, allowing dynamic memory management and easier code execution.

    CISC vs. RISC Architectures

    • CISC (Complex Instruction Set Computer): Features a large number of instructions, variable-length formats, and high-level operations directly manipulating memory.
    • RISC (Reduced Instruction Set Computer): Utilizes fewer instructions and addressing modes, emphasizes operations within registers, and features a fixed-length instruction format enabling single-cycle execution.

    x86 Addressing Modes

    • Immediate: Direct operand reference.
    • Register Operand: Access operand through a register.
    • Displacement: Effective address by adding a constant to a segment register.
    • Base with Displacement: Combines segment register, a base register, and a constant for effective address calculation.
    • Scaled Index with Displacement: Involves an index register multiplied by a scaling factor added to a base and displacement.
    • Relative: Moves address based on the program counter, aiding in code execution effectiveness.

    Context of Subroutines and Interrupts

    • Subroutines are managed through CALL and RETURN instructions, with context saved on the stack including Program Counter (PC) and Process State Word (PSW).
    • Interrupts can be external or internal signals, influencing the CPU’s flow of control and typically trigger a context switch.

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    Description

    Test your understanding of machine instructions and addressing modes in computer architecture. This quiz covers various types of instructions and their implications in embedded systems and microprocessors. Challenge yourself with questions designed for computer programmers and architects.

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