Memory Addressing Modes - OCR Computer Science A Level

Question	Answer
What are the 4 types of Memory Addressing Modes?	> Immediate > Direct > Indirect > Indexed
What is Immediate Addressing?	> Opcode is the actual value to be used (i.e., the CPU does not use RAM at all to get the value) > The CPU does not need to access another memory location as the data has already been given to it
What is Direct Addressing?	> Opcode is the address for the memory location where the actual data can be found > The CPU has to retrieve the value from the given memory location > LMC uses direct addressing
What is Indirect Addressing?	> Opcode is the location of the value to be used (usually a register) > This allows the CPU to access a higher number of locations, as it is not limited to the maximum value of the opcode, which is usually a small number of bits
What is Indexed Addressing?	> Opcode is one value added with another value stored in the index register > This final added value gives the memory location of the data to be used > Index register is a constant value - it represents the first memory location of an array of data

Resource summary

	Created by Malachy Moran-Tun over 2 years ago