The CPU Flashcards
What is the CPU?
The CPU (Central Processing Unit) is the hardware that executes programs and manages the rest of the hardware.
Who was Von Neumann?
Von Neumann used the idea of holding programs in memory and data would then move between the memory unit and the processor.
Name features about the RAM.
It’s Volatile - data is lost when turned off.
Stores user data/programs/part of operating system which is currently in use.
Memory can be written or read from.
What does RAM stand for?
Random Access Memory
Name components of the CPU
ALU (Arithmetic Logic Unit) CU (Control Unit) MDR (Memory Data Register) MAR (Memory Access Register)
PC (Program Counter) Accumulator (ACC) Current Instruction Register (CIR)
ALU
Logical Operations: These include AND, OR and NOT
Shift Operations: The bits in a computer word can be shifted left or right by a certain number of places
Arithmetic Operations: These include addition, subtraction, multiplication and division
MAR
MDR
The Memory Address Register holds the address (location in memory) of the instruction or piece of data to be fetched or stored.
When the data or program instruction is fetched from memory, it is temporarily held in the Memory Data Register.
PC
The Program Countermholds the memory address of the next instruction to be executed, which has heen fetched from memory and it temporarily held in the MDR before before being copied to the CIR.
Accumulator (ACC)
The Accumulator is one of the general purpose registers in which data and results of many operations are temporarily stored.
What does the decode part of the fetch execute cycle do?
The Control Unit decodes the instruction in the CIR to see what has to be done next.
What does the execute part of the cycle do?
The instruction is executed. Depending on what the instruction is, this could, for example, involve fetching data from memory and loading or addimg it into the accumulator or jumping to another instruction in the program.
What does the fetch part of the fetch execute cycle do?
The address A of the next instruction to be executed is copied from the PC to the MAR.
The PC is incremented so it piints to the next instruction to be fetched.
Simutaneously, the onstruction held im location A is then copied into the MDR.
The contents of the MDR are copied to the CIR.
