von Neumann Architecture

Memory Unit

The memory unit is reponsible for fetching and storing data and instructions from memory.  In older computers, the memory unit was a component of the northbridge. But with improvements in the manufacturing process of CPUs, the memory unit is now able to be included directly on the CPU.

Registers

Registers are the smallest but fastest form of memory in the computer.  They are stored on the CPU and can store values (addresses, instructions and data) with which the CPU is currently working.

Arithmetic/Logic Unit (ALU)

The ALU is the part of the processor which is able to perform calculations and comparisons.  It performs these operations on values stored in the registers.  If an operation has a result, such as an addition, then this result is also stored in a register. [1]

Control Unit

The control unit is responsible for scheduling and coordinating the work of all of the other parts of the computer. It sees to it that program instructions are carried out in the proper order.  It then decodes (decides what needs to be done with) the instructions.  Sometimes instructions will require other values from memory and the Control Unit will request these values from the memory unit. [1]