24.1.6. I/O Module Overview

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.

This chunk introduces the basic function of I/O devices which are responsible for input and output in a computer system. The screen displays the characters pressed on a keyboard, allowing users to see their actions in real-time. Printers serve as output devices that take information stored on hard disks and produce a physical copy.

Think of a computer as a waiter at a restaurant. When you give the waiter an order (input via keyboard), they write it down (displaying information on-screen) and then communicate that order to the chef (hard disk). The chef prepares the meal, and when it’s ready, the waiter brings it back to you (printing the information).

Similarly, we are having 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 at to switch on a machine or to work with a machine, sometimes we used to give password.

Machine readable devices serve different purposes than human readable ones. These devices facilitate monitoring and control. For instance, entering a password to unlock a machine is an example of machine-readable interaction where the system needs to verify the information before granting access.

Imagine a security gate at a concert. You need to scan your ticket (machine-readable information) to gain entry. Just like the password for a computer, the gate will only open if it recognizes your ticket as valid.

The third category we are talking about the storage devices. So, most of you know that you are having hard disk and many a time you said that the capacity of your hard disk is maybe your 500GB or 1 terabyte. So, what basically we are doing? We are storing our information in hard disks. So, when we are going to work with a computer, we bring the information from 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.

This chunk discusses storage devices, specifically hard disks, and their role in memory hierarchy. It explains how data storage works – information is stored in hard disks, but for processing, it's brought into main memory, and then the processor retrieves it from there for computations.

Think of hard disks as a warehouse where you keep your goods (data). When you need to use something, you retrieve it from the warehouse and bring it to your workspace (main memory), where you can process it. Finally, once you've completed your work, you might put the items back in the warehouse.

First we can talk about the registers inside a processor. Then next level is your main memory, then next level is you can say hard disk. So, this is the memory hierarchy and I think now, after going through this particular course...

The memory hierarchy refers to the different levels of storage available to a computer system, ordered by speed and size. Registers are the fastest but smallest, followed by cache, main memory, and then hard disks which have large storage capacity but are slower.

Imagine a teacher (the processor) who needs various teaching tools. The teacher keeps frequently used tools right at their desk (registers), occasionally using others stored in a nearby cabinet (cache). Tools not frequently used might be kept in a distant storage room (hard disk). To minimize time spent searching for tools, the teacher uses the closest resources first.

Now, what are the I/O module functions, already I have explained many more things. So, this is in nutshell you can say that. First one is your control and timing. So, this is the control circuit...

I/O modules serve several critical functions such as control and timing of operations between the CPU and devices, communication with the CPU, managing data buffering to account for speed differences between devices, and error detection during data transfer.

Picture a traffic cop (I/O module) directing cars (data) on busy roads (connections to devices). The cop ensures cars proceed smoothly without collisions (errors) and can manage different speeds of cars, ensuring everything flows at the right pace.

So, now, you just see that when I am explaining it, it is coming in a flow now. I think most of the things already I have mentioned when I discussed about this particular external device block diagram...

The I/O steps involve checking the status of devices, requesting data transfer, obtaining data from the device, and then transferring that data to the processor. This process outlines how data moves between the CPU and I/O devices systematically.

Consider a librarian (CPU) checking out books (data) to students (I/O devices). First, the librarian checks if a book is available (status check), then processes the checkout request (data transfer) and hands over the book to the student.

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