Understanding BCA Syllabus Avadh University – Semester I Paper BCA102 T Unit VI

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Semester I BCA Syllabus BCA102 T – Computer System Architecture

Semester I Paper BCA101 T Unit VI – Input-Output Organization

In Unit VI, we will explore Input-Output (I/O) Organization, a critical aspect of computer system architecture. I/O organization deals with how a computer communicates with external devices, allowing data exchange between the CPU and various peripherals. Let’s dive into these essential topics and understand their significance.

We will discuss the following:

Input / Output:

  • External Devices
    • I/O Modules
    • Programmed I/O
    • InterruptDriven I/O
    • Direct Memory Access
    • I/O Channels

Input / Output: Overview

What is Input / Output (I/O)?

Input / Output (I/O) refers to the process of sending data from external devices (inputs) to the computer and receiving data from the computer (outputs) to external devices. It allows users and applications to interact with the computer’s hardware.

Key Concepts in I/O Organization
  1. External Devices: These are hardware peripherals connected to the computer, such as keyboards, monitors, printers, disk drives, and network adapters.
  2. I/O Modules: These are specialized interfaces that facilitate communication between the CPU, memory, and external devices. They manage data transfer and control signals.

External Devices

What are External Devices?

External devices are hardware components or peripherals connected to a computer to provide input or output capabilities. They enable users to interact with the computer and expand its functionality.

Common External Devices

  1. Keyboards: Used for text input.
  2. Mice: Provide cursor control.
  3. Monitors: Display output.
  4. Printers: Produce hard copies of documents.
  5. Scanners: Convert physical documents into digital format.
  6. Storage Devices: Include hard drives, USB drives, and memory cards.
  7. Network Adapters: Enable network connectivity.

I/O Modules

What are I/O Modules?

I/O modules, also known as I/O controllers or I/O interfaces, are specialized hardware components responsible for managing communication between external devices and the CPU/memory. They handle data transfer and control signals.

Key Functions of I/O Modules
  1. Data Transfer: I/O modules facilitate the transfer of data between external devices and memory.
  2. Error Handling: They detect and report errors during data transfer.
  3. Interrupt Handling: I/O modules generate interrupts to alert the CPU when data is ready for processing.

Programmed I/O

What is Programmed I/O?

Programmed I/O is a method where the CPU actively polls or checks the status of I/O devices to determine when they are ready to send or receive data.

Practical Usage

# Example: Programmed I/O in Python
def read_keyboard():
    while not keyboard_ready():
        pass
    data = get_keyboard_data()
    return data

def write_display(data):
    while not display_ready():
        pass
    send_data_to_display(data)

In this Python code, the CPU actively checks if the keyboard and display are ready and then sends or receives data.

Interrupt-Driven I/O

What is Interrupt-Driven I/O?

Interrupt-driven I/O is a method where the CPU relies on interrupts to signal I/O devices when they are ready to send or receive data. The CPU can continue executing other tasks until an interrupt occurs.

Practical Usage
# Example: Interrupt-Driven I/O in Python
def keyboard_interrupt_handler():
    if keyboard_ready():
        data = get_keyboard_data()
        process_keyboard_input(data)

def display_interrupt_handler():
    if display_ready():
        data = get_data_to_display()
        display(data)

In this example, the CPU handles interrupts from the keyboard and display devices, allowing it to perform other tasks without active polling.

Direct Memory Access (DMA)

What is Direct Memory Access (DMA)?

DMA is a technique that allows I/O devices to transfer data directly to and from memory without CPU intervention. It improves I/O performance and reduces CPU overhead.

Practical Usage
# Example: DMA in Python
dma_controller.setup_dma_transfer(device, memory_address, data_size)
dma_controller.start_dma_transfer()

In this code, the DMA controller sets up and starts data transfer between an I/O device and memory, freeing the CPU from handling the entire process.

I/O Channels

What are I/O Channels?

I/O channels are specialized devices that manage multiple I/O devices and their data transfer. They offload much of the I/O processing from the CPU, enhancing efficiency.

Practical Usage

I/O channels are often found in mainframe computers and large server systems where extensive I/O operations are handled.

Conclusion

Understanding Input/Output (I/O) Organization is crucial for computer system architecture. External devices, I/O modules, programmed I/O, interrupt-driven I/O, DMA, and I/O channels collectively enable efficient communication between the CPU and peripherals. As future computer scientists and engineers, mastering these concepts is essential for designing responsive and high-performance computer systems.

Keep exploring and experimenting to deepen your understanding of I/O organization in computer architecture!

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