Basic Computer Organization and Design - stored program organization, instruction codes, computer registers, instruction cycle, timing and control, memory-reference instructions, input-output, interrupts - Question Bank

1. Which of the following is a characteristic of 'interrupts' in computer systems?
A) They are part of the normal sequential execution flow.
B) They allow for asynchronous handling of events from hardware or software.
C) They are only generated by the CPU.
D) They always result in program termination.
2. What is the fundamental difference between a computer with 'stored program organization' and earlier machines?
A) Earlier machines had separate memory for instructions and data.
B) Earlier machines could not perform arithmetic operations.
C) Earlier machines used vacuum tubes instead of transistors.
D) Earlier machines were not programmable.
3. In the instruction cycle, the 'operand fetch' is part of which main phase?
A) Fetch
B) Decode
C) Execute
D) Store
4. What is a common scenario that triggers an interrupt?
A) The CPU finishing a calculation.
B) A key being pressed on the keyboard or a disk drive completing a read operation.
C) The program counter reaching its maximum value.
D) The control unit sending a timing pulse.
5. What is the purpose of the 'control signals' generated by the control unit?
A) To store the final result of an operation.
B) To direct and synchronize the operations of all other components of the computer.
C) To fetch data from input devices.
D) To perform complex calculations.
6. Which register holds the current instruction after it has been fetched from memory?
A) Program Counter (PC)
B) Memory Address Register (MAR)
C) Instruction Register (IR)
D) Data Register (DR)
7. What is a 'micro-operation' in the context of the instruction cycle?
A) A complete instruction executed by the CPU.
B) A basic operation performed by hardware components, like moving data between registers or performing an ALU operation.
C) The process of fetching an instruction from memory.
D) The signal generated by the clock.
8. In a 'stored program' concept, what is the advantage of using a single memory for both instructions and data?
A) Increased hardware complexity.
B) Flexibility in allocating memory space between programs and data.
C) Faster execution for all operations.
D) Elimination of the need for a CPU.
9. What does 'memory organization' typically refer to?
A) The physical arrangement of CPU components.
B) The way memory is structured into addressable units and how it's accessed.
C) The design of input/output interfaces.
D) The logic gates used in the control unit.
10. What is the primary role of the 'fetch-decode-execute' cycle?
A) To manage power consumption.
B) To define the fundamental operation of a CPU.
C) To handle external device communication.
D) To optimize memory allocation.
11. Which type of instruction typically involves communication with peripheral devices?
A) Arithmetic instructions
B) Memory-reference instructions
C) Input/Output instructions
D) Control instructions
12. What is the purpose of a 'bus arbitration' mechanism?
A) To determine which device has access to the CPU.
B) To control the flow of data between different units connected by a bus.
C) To select the next instruction to be executed.
D) To manage interrupt priorities.
13. Which of these is a key challenge in designing the 'timing and control' unit for complex instruction sets?
A) Ensuring all instructions execute in a single clock cycle.
B) Managing micro-operations for a wide variety of instructions and addressing modes.
C) Minimizing the number of registers.
D) Eliminating the need for memory.
14. What is the significance of the 'instruction format' in computer design?
A) It dictates the number of input/output devices.
B) It defines the layout of bits for opcode, addressing modes, and operands.
C) It determines the clock speed of the processor.
D) It specifies the type of operating system.
15. A 'direct addressing mode' for memory-reference instructions means:
A) The address field of the instruction contains the effective address of the operand.
B) The operand is stored in a CPU register.
C) The address field contains the address of another memory location.
D) The instruction is executed immediately.
16. What is the primary function of the 'Memory Address Register' (MAR)?
A) To hold the data being read from or written to memory.
B) To hold the address of the memory location to be accessed.
C) To hold the instruction being decoded.
D) To hold the next instruction's address.
17. In the context of interrupts, what is an 'interrupt handler' or 'interrupt service routine' (ISR)?
A) The main program that is currently executing.
B) A special program designed to service the interrupt request.
C) The hardware component that detects the interrupt.
D) The register that stores the interrupt type.
18. Which component directly executes arithmetic and logical operations?
A) Control Unit (CU)
B) Memory Unit
C) Arithmetic Logic Unit (ALU)
D) Input/Output Module
19. What is the purpose of the 'status flags' or 'condition codes' in a CPU?
A) To store the next instruction address.
B) To indicate the result of an arithmetic or logical operation (e.g., zero, carry, negative).
C) To control the timing of operations.
D) To hold data being transferred.
20. The 'indirect addressing mode' for memory-reference instructions means:
A) The operand is directly specified in the instruction.
B) The address field of the instruction contains the address of the memory location that holds the effective address of the operand.
C) The operand is in a CPU register.
D) The instruction itself is stored in memory.
21. What is a 'halt' instruction used for?
A) To initiate an interrupt sequence.
B) To stop the execution of the program and the processor.
C) To transfer data from input devices.
D) To perform complex mathematical calculations.
22. Which type of instruction typically modifies the flow of program execution, such as branching or jumping?
A) Arithmetic instructions
B) Data transfer instructions
C) Control flow instructions
D) Input/output instructions
23. What is the main difference between a memory-reference instruction and a register-reference instruction?
A) Memory-reference instructions access memory, while register-reference instructions operate on CPU registers.
B) Memory-reference instructions are slower.
C) Register-reference instructions require an opcode and address.
D) Memory-reference instructions do not involve the ALU.
24. A 'bus' in computer organization refers to:
A) A type of memory storage.
B) A set of wires or pathways used for data and control signal transfer.
C) A specific CPU instruction.
D) An input device.
25. What is the purpose of incrementing the Program Counter (PC) after fetching an instruction?
A) To fetch the same instruction again.
B) To point to the next instruction in sequential execution.
C) To store the current instruction.
D) To indicate the completion of the fetch phase.
26. When the CPU fetches an instruction, it is typically placed into which register?
A) Memory Address Register (MAR)
B) Data Register (DR)
C) Instruction Register (IR)
D) Program Counter (PC)
27. What determines the speed and efficiency of the 'timing and control' unit?
A) The size of the memory.
B) The clock speed and the complexity of the control logic.
C) The number of input/output devices.
D) The type of programming language used.
28. The instruction 'ADD M' (Add content of memory to Accumulator) is an example of:
A) An I/O instruction
B) A register-reference instruction
C) A memory-reference instruction
D) A control instruction
29. Which of the following is NOT a typical component of a basic computer organization?
A) CPU
B) Memory
C) Input/Output Devices
D) Operating System
30. What is the role of the 'Accumulator' (AC) register in many CPU designs?
A) To hold the address of the next instruction.
B) To hold the data currently being operated on by the ALU and store the results.
C) To store intermediate results from memory.
D) To manage interrupt requests.
31. In a fixed-length instruction format, what is a common challenge?
A) Accommodating a wide range of opcodes and addresses efficiently.
B) Instructions are always executed faster.
C) Memory usage is always minimized.
D) The CPU design is simplified.
32. The 'operation code' (opcode) within an instruction code specifies:
A) The memory address for the data.
B) The device for I/O operations.
C) The action or operation to be performed by the CPU.
D) The next instruction's address.
33. Which register is often used to hold the data being transferred to or from memory?
A) Memory Address Register (MAR)
B) Program Counter (PC)
C) Data Register (DR)
D) Instruction Register (IR)
34. What is the typical sequence of events when an interrupt occurs?
A) CPU completes current instruction, saves state, jumps to interrupt handler, executes handler, restores state, resumes task.
B) CPU immediately stops, saves state, executes interrupt handler, resumes task.
C) CPU saves state, continues current task, executes interrupt handler later.
D) CPU ignores interrupt until all tasks are complete.
35. An 'interrupt' is a signal that:
A) Indicates the successful completion of a program.
B) Causes the CPU to temporarily stop its current task and service a request.
C) Is generated by the control unit to synchronize operations.
D) Is part of the normal instruction fetch cycle.
36. What is the primary purpose of 'input-output' (I/O) operations in a computer system?
A) To execute program instructions faster.
B) To allow the computer to communicate with the external world.
C) To manage the internal state of the CPU.
D) To store long-term program data.
37. Instructions like 'LOAD' and 'STORE' are classified as:
A) Arithmetic instructions
B) Logic instructions
C) Memory-reference instructions
D) Control flow instructions
38. What is a common example of a 'memory-reference instruction'?
A) ADD (add contents of a register to memory)
B) NOP (no operation)
C) JUMP (unconditional branch)
D) IN (input from device)
39. Which component is responsible for generating the sequence of control signals required to execute instructions?
A) Arithmetic Logic Unit (ALU)
B) Memory Unit
C) Input/Output Processor
D) Control Unit (CU)
40. What is the role of the 'Instruction Register' (IR)?
A) To hold the address of the next instruction.
B) To hold the current instruction being executed.
C) To hold data being processed by the ALU.
D) To hold the result of an arithmetic operation.
41. During the 'execute' phase of the instruction cycle, what typically occurs?
A) The instruction's address is loaded into the MAR.
B) The CPU performs the operation specified by the instruction.
C) The Program Counter is incremented.
D) The instruction is fetched from memory.
42. After fetching an instruction, the CPU decodes it. What happens during the decode phase?
A) The instruction is fetched from memory.
B) The instruction is sent to the ALU for execution.
C) The control unit interprets the instruction to determine the operation and operands.
D) The result of the operation is stored in a register.
43. The process of fetching an instruction from memory involves placing the instruction's address into which register?
A) Program Counter (PC)
B) Memory Address Register (MAR)
C) Instruction Register (IR)
D) Data Register (DR)
44. Which register typically holds the address of the next instruction to be fetched from memory?
A) Memory Address Register (MAR)
B) Program Counter (PC)
C) Instruction Register (IR)
D) Accumulator (AC)
45. A 'memory-reference instruction' is one that:
A) Performs an arithmetic operation on data within the CPU.
B) Transfers data between the CPU and an input/output device.
C) Accesses data or instructions from or to the main memory.
D) Changes the flow of program execution based on a condition.
46. What is the primary function of the 'timing and control' unit in a computer system?
A) To perform arithmetic and logical operations.
B) To store data and instructions.
C) To generate control signals that coordinate the operations of all other units.
D) To manage input and output devices.
47. The 'instruction cycle' of a CPU typically consists of which two main phases?
A) Fetch and Execute
B) Decode and Fetch
C) Execute and Store
D) Interrupt and Fetch
48. Which of the following is a typical 'computer register' used in a CPU?
A) Program Counter (PC)
B) Arithmetic Logic Unit (ALU)
C) Control Unit (CU)
D) Random Access Memory (RAM)
49. In a basic computer, what is an 'instruction code' primarily composed of?
A) Only the operation code (opcode) specifying the operation to be performed.
B) Only the address of the operand(s) involved in the operation.
C) An operation code (opcode) and one or more operand addresses or modes.
D) A status flag indicating the success or failure of the previous instruction.
50. What is the fundamental concept behind the 'stored program organization' in computer architecture?
A) Instructions and data are stored in separate memory units.
B) Instructions and data share the same memory space and are fetched by the CPU.
C) Instructions are hardwired into the CPU and cannot be changed.
D) Data is processed directly from input devices without being stored.
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