Jawaharlal Nehru Technological University Hyderabad B.Tech II COMPUTER ORGANIZATION AND ARCHITECTURE Previous Question Paper (March - 2022 - R18)

Computer Architecture refers to the conceptual structure and functional behavior of a computer system as seen by the programmer. It focuses on the attributes of a system that have a direct impact on the logical execution of a program, such as the instruction set architecture (ISA), number of bits used for data representation, I/O mechanisms, and addressing techniques. It defines the 'what' of the machine, establishing the interface between hardware and software.

Computer Design, or computer organization, refers to the operational units and their interconnections that realize the architectural specifications. It deals with the implementation details, such as control signals, interfaces, memory technology, and the physical design of the processor. While architecture is concerned with the instruction set, design is concerned with how those instructions are executed through hardware components like the ALU, registers, and control units. In essence, computer architecture defines the system's capabilities, while computer design determines how those capabilities are physically and logically constructed to achieve performance and efficiency.

The life cycle of an instruction, often referred to as the instruction cycle, consists of a sequence of steps that the CPU performs to execute a single machine instruction. The cycle is generally divided into the following phases:

1. Fetch: The CPU fetches the next instruction from the memory address stored in the Program Counter (PC). The instruction is loaded into the Instruction Register (IR), and the PC is incremented to point to the next instruction.
2. Decode: The control unit interprets the instruction in the IR to determine the operation to be performed and the operands involved. This involves identifying the opcode and addressing modes.
3. Execute: The CPU performs the actual operation specified by the instruction. This may involve ALU operations, data movement between registers and memory, or branching.
4. Store/Write-back: The result of the execution is written back to the destination, which could be a register or a memory location, completing the instruction's effect on the system state.