Input/Output Techniques - 24.6 | 24. External Devices and Their Types | Computer Organisation and Architecture - Vol 3
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Introduction to I/O Devices

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0:00
Teacher
Teacher

Today, we're going to introduce the concept of input/output devices. Can anyone tell me what an input device is?

Student 1
Student 1

Isn't it something like a keyboard or a mouse?

Teacher
Teacher

Exactly! Input devices allow us to enter data into the computer. Now, what about output devices?

Student 2
Student 2

I think output devices show us the results, like monitors or printers.

Teacher
Teacher

Correct! Output devices display processed data. What are some examples of machine-readable devices?

Student 3
Student 3

Maybe like a barcode scanner or a QR code reader?

Teacher
Teacher

Great examples! Remember, human-readable devices allow direct interaction with the user, while machine-readable devices facilitate interaction between devices for monitoring and controlling systems.

Teacher
Teacher

In summary, input devices let us provide data, while output devices convey information back to us.

Memory Hierarchy

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Teacher
Teacher

Let’s move on to memory hierarchy. Can anyone tell me where registers fit in?

Student 4
Student 4

I think registers are the fastest part of the memory.

Teacher
Teacher

Exactly, registers are at the top of the hierarchy! What comes next?

Student 1
Student 1

Cache memory is next, I believe.

Teacher
Teacher

Yes, good! And then we have main memory followed by storage devices like hard disks. What trend do you notice as we move down the hierarchy?

Student 2
Student 2

The speed decreases, but the capacity increases.

Teacher
Teacher

That's correct! Speed decreases and capacity increases, while the cost per unit memory also varies. Well done!

I/O Module Functions

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Teacher
Teacher

Now, let's discuss I/O module functions. What do you think is the primary duty of an I/O module?

Student 3
Student 3

I think it manages data flow between the CPU and the devices.

Teacher
Teacher

Exactly! The I/O module controls timing, data buffering, and error detection as well. Can anyone explain what happens during data buffering?

Student 4
Student 4

Isn’t that when data is temporarily stored before being sent to the CPU?

Teacher
Teacher

Correct! The I/O module gathers enough data before transferring it to match the speeds of devices and the CPU. Excellent understanding!

I/O Transfer Techniques

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Teacher
Teacher

Finally, let's explore I/O transfer techniques. Can someone tell me about programmed I/O?

Student 1
Student 1

In programmed I/O, the CPU checks the device status repeatedly.

Teacher
Teacher

Exactly! What is a major drawback of this method?

Student 2
Student 2

It wastes CPU time since it’s stuck waiting.

Teacher
Teacher

Right. Now, what about interrupt-driven I/O?

Student 3
Student 3

The CPU can continue working while it waits for an interrupt from the I/O module.

Teacher
Teacher

Perfect! Lastly, let’s discuss DMA.

Student 4
Student 4

DMA allows devices to transfer data directly to memory without the CPU's intervention.

Teacher
Teacher

Great summary! In summary, we discussed programmed I/O, where the CPU directly manages data transfer and can waste time; interrupt-driven I/O, which allows multitasking, and DMA, which enhances efficiency by bypassing the CPU in data transfer.

Introduction & Overview

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Quick Overview

This section explores input/output (I/O) techniques, highlighting the differences between human-readable and machine-readable devices, as well as the various methods of I/O data transfer.

Standard

The section provides an overview of input/output techniques used in computers, describing the roles of different devices, the memory hierarchy, and the functions of I/O modules. It discusses programmed I/O, interrupt-driven I/O, and direct memory access (DMA) as methods of data transfer, while also introducing essential I/O module functions.

Detailed

Detailed Summary

In this section, we delve into the input/output (I/O) techniques that enhance data interaction between the user and the computer system. Input devices like keyboards and mouse allow users to provide commands and data, while output devices such as monitors and printers present processed information back to users. The distinction between human-readable devices and machine-readable devices is essential for understanding how information is captured and reported.

We also examine the memory hierarchy, which ranges from fast and limited registers to expansive but slower storage devices like hard drives. This hierarchy is critical as each level serves distinct purposes in terms of speed and capacity.

The section further explains I/O module functions—including control and timing, CPU communication, device communication, data buffering, and error detection—illustrating their significance in managing the interactions between the CPU and various devices.

We explore three main data transfer techniques: programmed I/O, where the CPU checks and waits for device readiness; interrupt-driven I/O, which allows the CPU to perform other tasks while waiting for the device to signal readiness; and Direct Memory Access (DMA), which enables efficient data transfer directly between devices and memory without CPU intervention.

Understanding these concepts forms the foundation for effectively leveraging input/output techniques in computer systems.

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Overview of Input/Output Devices

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So, like that screen. If we are displaying something or say if you press some keys in the keyboard then that character will be displayed in the screen. Similarly printer, so if we are storing something in our hard disk. Now we can transfer it to the printer and we can print it. So, these are basically human readable devices; like screen, printer, keyboard and like that.

Detailed Explanation

This chunk discusses the role of various input/output (I/O) devices in computer systems. Input devices like keyboards allow users to enter data, while output devices like screens and printers display or print that data. Together, they serve as the interface between the computer and the user, making interaction possible.

Examples & Analogies

Consider a classroom where the teacher writes on a board (input) and the students view the content (output). Just like a teacher uses a chalk to create visible information for students, computers use devices like keyboards and screens to mix input with output experiences.

Machine Readable Devices

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Similarly, we have some devices which are machine readable. So, this machine readable devices are basically used for monitoring and controlling purposes. So, in this particular case I can give a simple example. So, when we are using our computer to switch on a machine or to work with a machine, sometimes we use a password. So, when you enter a password then only you can enter into the machine and you can work with the machine.

Detailed Explanation

This chunk explains the concept of machine-readable devices, which are used for tasks such as monitoring and controlling systems. The example given is of passwords used to access computers or machines, demonstrating how these devices ensure that only authorized users can gain access.

Examples & Analogies

Imagine a secure room that only certain personnel can enter. Just as a security guard checks IDs before granting access, machine-readable devices like password systems check if the incoming data meets a preset condition (correct password) before allowing access.

Storage Devices and Memory Hierarchy

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Now, this is the password, it is a string of characters generally we use, but instead of that we can use some devices also some other features to unlock the computer like one simple example is your fingerprint. [...] So, when we are going to work with a computer, we bring the information from the hard disk to the main memory and processor is going to take the information from main memory and it will be going to put into the registers that we have inside the processor.

Detailed Explanation

This chunk discusses different methods of accessing computers, including traditional passwords and biometric data like fingerprints. It then explains the process by which data is transferred from storage devices (like hard disks) into the computer's memory and registers for processing.

Examples & Analogies

Think of accessing a bank vault. Just like a password gives you initial access, a fingerprint can provide an extra layer of security. Once inside, the vault (hard disk) holds cash or jewels (data), which the banker (processor) retrieves to serve customers (perform operations).

The Idea of Device Controllers and Transducers

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So, we are having a control logic over here. This control logic is going to receive the control signals from I/O module. [...] So, this is the way we can look into; that means, you just see that, in the hierarchy now we are having three component; one is your processor, I/O module is connected to the processor and the devices are connected to the I/O module.

Detailed Explanation

This chunk explains the role of control logic in managing I/O devices. It describes how control signals from the I/O module facilitate communication between the processor and connected devices. Device controllers are crucial for converting commands into actions and ensuring smooth operation.

Examples & Analogies

Consider a conductor of an orchestra. Just as the conductor signals different musicians (instruments) on when to play (control signals), the control logic tells devices (like printers and hard drives) when to execute tasks, making the whole system perform harmoniously.

Input and Output Module Functions

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Now, what are the I/O module functions, already I have explained many more things. So, this is in nutshell you can say that. [...] So, I/O module is responsible for control and timing, CPU communication, device communication, another one is data buffering.

Detailed Explanation

In this chunk, the functions of the I/O module are summarized. It handles control timing, enables communication between the CPU and devices, and manages data buffering to ensure that data flows smoothly despite the differing speeds of devices.

Examples & Analogies

Imagine a traffic cop directing cars at a busy intersection. The cop ensures that cars (data) move efficiently without collision (buffering). Without the cop, traffic would be chaotic. Similarly, the I/O module manages data traffic between the CPU and peripheral devices.

I/O Steps in Data Transfer

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Now you just see that when I am explaining it, it is coming in a flow now. [...] But if you are reading a file then it may be an input operation.

Detailed Explanation

This section outlines the sequential steps taken during data transfer in input/output operations. It highlights how the CPU checks device status, requests data transfer, and how the I/O module retrieves data from devices to send to the CPU, establishing a clear flow of information.

Examples & Analogies

Think of a librarian checking if a book is available (device status) before fetching it for a reader. The librarian ensures the book is ready and available before handing it over, similar to how the CPU interacts with the I/O module to ensure data is fetched efficiently.

Input/Output Techniques Overview

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So, if you are looking into that way of transferring information. [...] So, in that particular case what will happen? Now say when we want to read a file from the hard disk to the processor memory, then what will happen?

Detailed Explanation

This final chunk introduces various input/output techniques that manage data transfer, including programmed I/O, interrupt-driven I/O, and direct memory access (DMA). Each technique has its own methods and efficiencies in managing interactions between the CPU and devices.

Examples & Analogies

Think of three different methods of sending a message: a handwritten note (programmed I/O, which can be slow), a notification alerting the recipient when the note is ready to be read (interrupt-driven I/O), or a direct delivery system that sends the message automatically without needing to track it (DMA). Each method varies in efficiency and speed.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Human-Readable Devices: Devices like keyboards and monitors that users can interact with directly.

  • Machine-Readable Devices: Devices designed for computer processing without direct human intervention.

  • Memory Hierarchy: The structured layering of storage types that vary in speed, cost, and capacity.

  • I/O Module Functions: Responsibilities including control, data buffering, and error detection.

  • Transfer Techniques: Different methods for data transfer (programmed I/O, interrupt-driven I/O, DMA) that can optimize CPU utilization.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • A keyboard as an input device where users type commands.

  • A printer as an output device that produces hard copies of documents.

  • Using a barcode scanner as a machine-readable device for inventory management.

  • The transfer of data from a hard disk to RAM via DMA without CPU waiting.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • For I/O devices, listen to this chime, input from users, output's on time.

📖 Fascinating Stories

  • Once upon a time in a computer land, devices communicated just as we planned. Input on one side, output on the other, they worked hand in hand, like sister and brother.

🧠 Other Memory Gems

  • Remember as I/O: Input is what goes in, Output is what comes out!

🎯 Super Acronyms

I.D. for I/O

  • Input Devices for communication and Output Devices for presentation.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Input Device

    Definition:

    A device that allows users to provide data and commands to a computer.

  • Term: Output Device

    Definition:

    A device that displays or prints information processed by the computer.

  • Term: Machinereadable Device

    Definition:

    Devices that rely on signals to be processed by a computer without direct human interpretation.

  • Term: Memory Hierarchy

    Definition:

    An arrangement of storage types in a computer system, ordered by speed, size, and cost.

  • Term: I/O Module

    Definition:

    A component that manages data transfer between the CPU and peripheral devices.

  • Term: Programmed I/O

    Definition:

    A technique where the CPU waits for I/O device status checks before proceeding.

  • Term: Interruptdriven I/O

    Definition:

    A method where the CPU performs tasks while waiting for an I/O operation to signal completion.

  • Term: Direct Memory Access (DMA)

    Definition:

    A technique allowing devices to transfer data directly to memory without CPU involvement.