Q.1 Name and explain all the registers found in CPU of computer.

Answer :
Registers - CPU contains a few special purpose, temporary storage units known as registers. They are high-speed memory locations used for holding instructions, data and intermediate results that are currently being processed. There are following types of registers to hold different types of information -

(1) Program Counter (PC) - It is used to keep track of the next instruction to be executed. It holds the address of the memory location which contains the next instruction to be fetched from the memory. After an instruction has been fetched, its content is automatically incremented assuming that instructions are normally executed sequentially. For a jump instruction, its contents are modified and program jumps to the memory location which contains the desired instruction to be executed next.

(2) Instruction Register (IR) – It holds instructions to be decoded by the control unit. Instruction register contains the 8-bit opcode instruction being executed. Some computers have two instructions register so that they can fetch and save the next instruction while the execution of the previous instruction is going on.

(3) Memory Address Register (MAR) - It holds the address of the next location in the memory to be accessed.

(4) Memory Buffer Register (MBR) - It stores data received from or sent to CPU.

(5) Memory Data Register (MDR) - It stores operands and data.

(6) Accumulator (ACC) - It stores the intermediate results produced by arithmetic and logic unit.