Addressing Modes in Computer Architecture
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Addressing Modes in Computer Architecture

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Questions and Answers

What is the main advantage of register addressing mode?

  • It is easier to implement than direct addressing.
  • It allows larger address spaces.
  • It has no limitations in address field length.
  • It requires fewer memory references. (correct)
  • In displacement addressing mode, how is the effective address (EA) calculated?

  • EA = A + immediate value
  • EA = A + content of a register (correct)
  • EA = A - content of a register
  • EA = content of a register + immediate value
  • Which addressing modes are considered common uses of displacement addressing?

  • Direct addressing, register addressing, relative addressing
  • Relative addressing, base-register addressing, indexing (correct)
  • Indirect addressing, base addressing, direct addressing
  • Absolute addressing, base-register addressing, indexing
  • What is a disadvantage of register addressing?

    <p>It has a very limited address space.</p> Signup and view all the answers

    What does indirect addressing involve?

    <p>Referencing a location in memory that contains an address.</p> Signup and view all the answers

    What does the op-code field in an instruction represent?

    <p>The operation to be performed</p> Signup and view all the answers

    Which of the following is an advantage of immediate addressing mode?

    <p>It can define and use constants directly in the instruction.</p> Signup and view all the answers

    What limitation does immediate addressing mode have?

    <p>Restricts the size of the constant to the address field.</p> Signup and view all the answers

    In direct addressing mode, what does the address field contain?

    <p>The effective address of the operand</p> Signup and view all the answers

    What is a notable difference between direct addressing and indirect addressing modes?

    <p>Indirect addressing uses the address of a word in memory.</p> Signup and view all the answers

    What happens during the execution of the instruction 'LOAD 1000, Ri' in direct addressing mode if the memory location 1000 contains 2345?

    <p>The value 2345 is loaded into register Ri.</p> Signup and view all the answers

    Which of the following addressing modes provides limited address space due to direct specification of an address?

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

    Which addressing mode avoids any special calculations by directly referencing the operand's address?

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

    Study Notes

    Addressing Modes

    • The way the CPU accesses information needed for operations is called addressing
    • Operand is the information being accessed
    • Instructions need:
      • Op-code which defines the operation
      • Address field which defines location of operand
    • Addressing modes differentiate based on how the address of the operand is specified

    Immediate Addressing

    • The value of the operand is directly included within the instruction
    • Used for constants, initial variable values
    • Advantage: No extra memory reference needed, improves efficiency
    • Disadvantage: Limited operand size, restricted by address field size, must be known at assembly time
    • Example: ADD 5 : The number 5 is directly stored in the instruction for addition

    Direct Addressing Mode

    • Address field contains the direct address of the operand
    • Requires only one memory reference, minimal calculation
    • Limitation: Limited address space
    • Example: LOAD 1000, Ri : If memory location 1000 contains value 2345, the instruction will load value 2345 into register Ri

    Indirect Addressing Mode

    • Address field refers to a memory location that stores the actual address of the operand
    • Useful for address range limitations of the address field
    • Example: Add 100 : Memory location 100 contains another address, which points to the data to be added

    Register addressing Mode

    • Address field refers to a register that holds the operand
    • Similar to Direct Addressing, but uses register instead of memory
    • Advantages: Smaller address field, faster access due to no memory reference
    • Disadvantage: Very limited address space
    • Example: ADD R1 : The value stored in register R1 is used for the addition operation

    Displacement Addressing Mode

    • Requires two address fields, at least one explicit
    • One field includes a direct value (A)
    • The other field refers to a register (R)
    • Effective Address (EA): Calculated as A + (R)
    • Common uses:
      • Relative Addressing: A is a relative offset, R points to a base address
      • Base-Register Addressing: R is a base register, A is an offset from the base
      • Indexing: R is an index register, A is a base address, EA points to an element within a data structure

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    Description

    This quiz explores various addressing modes used in computer architecture, focusing on immediate and direct addressing. You'll learn how operands are accessed and the advantages and disadvantages of each mode. Test your knowledge on how these modes influence CPU efficiency and memory access.

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