Introduction to Computer Organization : MCQs & PYQs with Explanation

Option B

The CPU executes instructions in a fixed sequence, fetching the instruction from memory, decoding it, and then executing it. The total time taken to complete one full instruction, including both fetching and execution, is called a CPU cycle or instruction cycle.

Option C

The Data Bus is a set of parallel lines used to transfer data between the CPU, memory, and input/output devices.
The width of the data bus determines how many bits of data can be transferred simultaneously in a single clock cycle. A wider data bus allows more bits to be moved at the same time, which reduces the number of transfers required to move large amounts of data. 
As a result, the CPU can fetch instructions and data faster, leading to an improvement in the overall processing speed of the computer.

• Data Bus : What data is transferred.
• Address Bus : Where data is transferred.
• Control Bus : How and when data is transferred.

Option A

In a computer system, signals travel through the bus lines to transfer data, addresses, and control information between the CPU, memory, and I/O devices. 
However, signals do not travel instantaneously, they require a small amount of time to move from one device to another. This time is known as Propagation Delay.
Propagation Delay is the time required for a signal to travel through the bus from the sender to the receiver. It affects how quickly different devices can coordinate and communicate over the bus.

Note:

• Clock Delay (Clock Skew) is the difference in time taken by the same clock signal to reach different components of a computer system.
• A Clock Signal is an electronic signal that generates regular pulses and is used to synchronize all operations inside a computer. It acts like a Timer that tells the CPU and other components when to perform an operation.

Option D

A System Bus is a set of communication lines that connects the CPU, memory, and input/output devices. It is responsible for transferring data, addresses, and control signals among different components of a computer system.
A system bus consists of three main types of lines:

• Data Lines (Data Bus)
• Address Lines (Address Bus)
• Control Lines (Control Bus)

Control Lines are used to control the access to and use of the data and address lines. They carry signals such as:

• Read signal.
• Write signal.
• Interrupt signal.
• Clock signal.
• Memory access signal.

These signals coordinate communication between the CPU, memory, and I/O devices and ensure that data is transferred correctly.

Option C

The Interface Unit is used to manage communication between the CPU and peripheral devices such as keyboard, printer, mouse, and monitor.
CPU works at a very high speed, while peripheral devices usually work at lower speeds and use different data formats. The interface unit helps in resolving this speed and communication difference.
The interface unit acts as a bridge between the CPU and input/output devices.

Option A

A Bus is a communication pathway that connects different components of a computer and allows them to exchange data, addresses, and control signals. It acts like a road or highway inside the computer through which information travels between:

• CPU.
• Memory (RAM).
• Input Devices.
• Output Devices.

A computer bus is generally divided into three types:

• Memory is used to store data and instructions.
• A UPS (Uninterruptible Power Supply) provides backup power during power failures.
• The Control Unit manages and coordinates the operations of the computer.

Option A

A computer uses various interfaces and communication ports to connect peripheral devices such as hard disks, printers, scanners, keyboards, and other external devices. Different interfaces are designed for different purposes and data transfer requirements.
The Statement (i) is True. SCSI (Small Computer System Interface) is a bus/interface standard used to connect peripheral devices such as:

• Hard Disk Drives
• CD/DVD Drives
• Scanners
• Printers
• Tape Drives

It provides a communication path between the computer and these devices.
The Statement (ii) is True. A Serial Port transfers data one bit at a time. In older computer systems, serial ports were commonly used to connect:

• Printers
• Scanners
• Modems
• Mice

Although modern devices mostly use USB ports, serial ports were widely used for printers and scanners.

Option B

MISD is a type of computer architecture classification given in Flynn’s Classification. It describes how instructions and data streams are processed in parallel computing systems.
MISD stands for Multiple Instruction Stream and Single Data Stream. In MISD architecture, multiple processors execute different instructions on the same data stream simultaneously.

Option B

A Buffer is a temporary storage area used to adjust the difference in data transfer speeds between two devices. When one device sends data faster than the other can receive it, the buffer temporarily holds the data and releases it at a suitable rate. This prevents data loss and ensures smooth data flow.

Option A

The Control Unit (CU) is the part of the CPU that controls and supervises the execution of every instruction. It fetches instructions from memory, decodes them, and then generates the necessary control signals to ensure that each step of the instruction is performed in the correct sequence.
The control unit directs other components such as the ALU, Registers, and Memory on what operations to perform and when to perform them.

• The Accumulator is used to store intermediate results.
• The ALU performs arithmetic and logical operations.
• A Control Register only stores control-related information.

Option D

In Von Neumann architecture, a computer uses one single memory to store both data and program instructions. The CPU fetches instructions and data from the same memory using the same buses. 
This design makes the system simple, but it can cause a performance limitation known as the Von Neumann bottleneck, because data and instructions cannot be accessed at the same time.

Option C

Microprogrammed control units store a sequence of microinstructions in control memory, which makes it easier to implement and modify instructions. This is because changes can be made by updating microcode rather than redesigning hardware logic.

Option D

In a computer system, input/output commands are used for communication between the CPU and peripheral devices through an Interface Unit. During a data input operation, data is transferred from the input device to the CPU through the interface registers and system bus.
The data input command causes the interface to place its stored data onto the bus so that the CPU can read it.
For example, when a keyboard sends data to the CPU, the interface transfers the entered data from its register to the data bus.

Option C

A Data Bus is used to transfer data between the CPU, memory, and input/output devices. The number of parallel lines (or wires) present in the data bus is called the width of the data bus.
The width determines how many bits of data can be transferred at one time. A wider data bus can transfer more data simultaneously, which improves the overall performance of the computer system.
E.g.:

• An 8-bit data bus has 8 lines and can transfer 8 bits of data at a time.
• A 16-bit data bus has 16 lines and can transfer 16 bits of data at a time.
• A 32-bit data bus has 32 lines and can transfer 32 bits of data at a time.
• A 64-bit data bus has 64 lines and can transfer 64 bits of data at a time.

The Volatility refers to whether memory retains data after power is turned off.

Option A

A Stored Program machine is a computer system in which both the program instructions and the data are stored in the same memory. This concept is based on the von Neumann architecture, where instructions can be stored, modified, and executed from memory.
A micro-computer such as a desktop or personal computer follows the stored program concept. It stores programs and data in its main memory and executes instructions sequentially as required.