CPU and Memory

CPU and Memory

1. The CPU is the Central Processing Unit of the computer, it is often referred to as the processor. The CPU has two main components: the Control Unit & the Arithmatic and Logic Unit

   • The control unit (CU) controls the hardware and software devices and performs the Fetch, decode, execute cycle
     • The control unit is responsible for informing the system what to do so that instructions are executed - a bit like a teacher assigning work to a class. It also manages all of the computers programs by directing the flow of data between the CPU and other devices The CU also controls an instruction register that can transfer instructions or data and perform arithmetic and logical comparisons at high speed. Registers are used by the CU as temporary, convenient places to store the information necessary to decode and execute. It also must communicates with both the arithmetic logic unit and main memory
   • The AUL performs arithmatic and logical operations
     • The arithmetic logic unit receives coded instructions from the control unit to complete the required calculations or operations - like a powerful calculator. The result of these calculations are stored in an output register. Some of the calculations ALU carries out: -comparisons : use relational operators (=, <, >) to determine the relationship between values - logical operations: use the logic gates AND , OR and NOT

2. The CPU communicates between the input and output device and the memory. It recieves instructions from the binary pattern, thes instructions are written in machine code and enable the CPU to perform calculations. The result of these calculations is stored in the CPU's main memory, referred to as the IAS (Immeadiate Acess Storage). The results then inform the CPU what instructions to relay to the input andoutput devices - this is known as the fetch, decode, execute cycle.

   • FETCH – instructions are fetched from the memory DECODE – instructions are decoded and prepared EXECUTE – instructions are executed

3. When a calculation is complete, the data is encoded as bit patterns using the binary number system. These bit patterns are stored in memory addresses. Memory addresses identify locations in a computers storage memory. Every memory address is numbered consecutively and stores each part of the instruction in the correct order