COMPUTER ADDRESSING MODES

The different computers available in the world are having different addressing modes. The addressing mode specifies a rule for interpreting or modifying the address field of the instruction much before the operand is actually referenced. The addressing modes provide programming flexibility to the user and to use the bits in the address field of the instruction efficiently. In the very simple term, we can say that the addressing modes specify the way operands are stored. The simple computer available is provided by at least ten addressing modes. In implied mode the address of the operands are specified implicitly in the definition of the instruction i.e. no need to specify address in the instruction. In immediate mode, instead of specifying the address of the operand, operand itself is specified. There is no need to specify address in the instruction however, operand itself needs to be specified.

This mode sometimes, requires more bits than the address and it is fast to acquire an operand. The college of computer science and applications of IIMT University, Meerut which is rated as Best private university in UP as computer architecture and organization is the part of curriculum for the computer science students. In register addressing mode, address specified in the instruction is the register address and the designated operand need to be in a register. The address is shorter address than the memory address and it faster to acquire an operand than the memory addressing. In register indirect mode the instruction specifies a register which contains the memory address of the operand it saves instruction bits since register address is shorter than the memory address. This addressing mode is slower to acquire an operand than both the register addressing and memory addressing.

Auto-increment or Auto-decrement addressing modes are same as the register indirect, but when the address in the register is used to access memory, the value in the register is incremented or decremented by 1 (after or before the execution of the instruction). In direct address mode the instruction specifies the memory address which can be used directly to the physical memory and it is faster than the other memory addressing modes.

In indirect addressing mode the address field of an instruction specifies the address of a memory location that contains the address of the operand, when the abbreviated address is used large physical memory can be addressed with a relatively small number of bits. While in relative addressing mode, the address fields of an instruction specifies the part of the address which can be used along with a designated register to calculate the address of the operand. The college of computer science and applications of IIMT University, Meerut which is rated as Best private university in UP is providing moral education along with technical education.

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Created on Jun 11th 2018 01:04. Viewed 264 times.

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