REGISTER

WHAT IS A REGISTER ?

• The computer hardware for storing one machine word.

• A small, high-speed computer circuit that holds values of internal operations, such as the address of the instruction being executed and the data being processed.

• When a program is debugged, register contents may be analyzed to determine the computer's status at the time of failure.

• In microcomputer assembly language programming, programmers look at the contents of registers routinely. Assembly languages in larger computers are often at a higher level.

INSTRUCTION EXECUTION CYCLE

THE INSTRUCTION EXECUTION CYCLE.

The instruction execution cycle is included with the following steps;

1.FETCHES

2.DECODE

3.EXECUTE

4.STORE

HOW THE CPU EXECUTES PROGRAM INSTRUCTION ?

 Before an instruction can be executed,program instructions and data must be placed into memory from an input device or a secondary storage device.

1.  The control unit "FETCHES" (gets) the instruction from the memory.
2. The control unit "DECODES" (decides what it means) the instruction and gives instruction for necessary  data to be moved from memory to the arithmetic/logic unit.
3. The arithmetic/logic unit "EXECUTES" arithmetic and logic instruction.That is, the ALU is given control and performs the actual operation on the data.
4. The result of these operation is "STORED" in memory or in a temporary location called a register.
   

RAM-Random Access Memory

• RAM chips are called temporary or volatile storage because their contents are lost if power is disrupted.

• RAM chips hold the program and data that the CPU is presently processing.

TYPES OF RAM

• CACHE MEMORY-Improves processing by acting as a temporary high-speed holding area   between the memory and CPU.
• DIMM (dual-in-line memory module)-Used to expand memory
 
 

ROM aka Read-Only-Memory

ROM chips have information stored in them by manufacturer.

The characteristics of ROM are :

• not volatile
• cannot be changed by the user
• "read only" means that the CPU can read ,or retrieve , data and programs written on the ROM chip.
• computer cannot write-encode or change-the information or instructions in ROM.
• ROM chips typically contain special instructions for detailed computer operations.