Jawaharlal Nehru Technological University Hyderabad B.Tech III COMPUTER ORGANIZATION AND OPERATING SYSTEMS Previous Question Paper (November/December - 2020 - R16)

The basic operational concepts of a computer revolve around the interaction between the Central Processing Unit (CPU), Memory, and Input/Output (I/O) units. The CPU acts as the brain, containing the Arithmetic Logic Unit (ALU) for data processing and the Control Unit (CU) to manage operations. The Memory unit stores data and instructions, while I/O units facilitate communication with the external environment.

The operational cycle follows these steps: 1. Input: Data is entered via input devices and stored in memory. 2. Processing: The CPU fetches instructions from memory, decodes them, and executes the required arithmetic or logical operations. 3. Output: The processed results are sent to output devices. 4. Storage: Data is kept in memory or secondary storage for future use. The system components are interconnected by a system bus consisting of the data bus, address bus, and control bus.

Register transfer refers to the movement of data between registers within the CPU. This is typically represented using Register Transfer Language (RTL), where a transfer is denoted as: R2 ← R1. This indicates that the contents of register R1 are loaded into register R2 through a common bus or direct connection.

A bus system is a set of common lines used to transfer information between multiple registers. It is implemented using multiplexers or three-state buffers. To transfer data from a source register to a destination register, the control signals select the specific source onto the bus and enable the load input of the destination register.

Memory transfers involve moving data between the CPU and the Memory unit. This process uses two primary registers: the Memory Address Register (MAR) and the Memory Data Register (MDR). For a memory read operation, the address is placed in the MAR, and the memory control unit places the data at that address onto the data bus to be loaded into the MDR. For a memory write operation, the address is placed in the MAR, the data to be stored is placed in the MDR, and a write control signal is issued to store the data into the specified memory location.