Types of Addressing Modes

Addressing Modes

Addressing modes determine how the memory address of an operand is calculated.

Types of Addressing Modes

1. Immediate Addressing Mode
   • The operand is specified directly in the instruction.
   • Example:

     MOV AX, 5

     (Move the value 5 to the AX register)
2. Register Addressing Mode
   • The operand is stored in a register.
   • Example:

     MOV AX, BX

     (Move the contents of the BX register to the AX register)
3. Direct Addressing Mode
   • The memory address of the operand is specified directly in the instruction.
   • Example:

     MOV AX, [1000h]

     (Move the contents of memory location 1000h to the AX register)
4. Indirect Addressing Mode
   • The memory address of the operand is stored in a register or memory location.
   • Example:

     MOV AX, [BX]

     (Move the contents of the memory location pointed to by the BX register to the AX register)
5. Indexed Addressing Mode
   • The memory address of the operand is calculated by adding an index value to a base address.
   • Example:

     MOV AX, [BX + 4]

     (Move the contents of the memory location pointed to by the BX register plus 4 to the AX register)
6. Base-Indexed Addressing Mode
   • The memory address of the operand is calculated by adding a base address and an index value.
   • Example:

     MOV AX, [EBX + ESI]

     (Move the contents of the memory location pointed to by the sum of the EBX and ESI registers to the AX register)
7. Relative Addressing Mode
   • The memory address of the operand is calculated relative to the current instruction pointer.
   • Example:

     JMP LABEL

     (Jump to the instruction labeled LABEL)

Importance of Addressing Modes

• Addressing modes provide flexibility and efficiency in programming and data access.
• Understanding addressing modes is crucial for programming and computer architecture.
• Different addressing modes are used in different contexts, such as:
  • Immediate addressing mode is used for loading constants.
  • Register addressing mode is used for register-to-register operations.
  • Direct addressing mode is used for accessing memory locations.
  • Indirect addressing mode is used for dynamic memory allocation.
  • Indexed addressing mode is used for array operations.
  • Base-indexed addressing mode is used for structure and class operations.
  • Relative addressing mode is used for branching and looping.