24.4.1. Connection to Processor

So, these are basically human readable devices; like screen, printer, keyboard and like that.

Human-readable devices are those that allow users to interact with digital content in a way that is intuitive and understandable. A keyboard allows us to input commands, a screen displays information visually, and a printer takes the information from our computer and produces a physical representation of it on paper. These devices serve as the primary means through which we communicate with computers and receive outputs in a form that makes sense to us.

Imagine trying to write a letter. You use a keyboard (input) to type your thoughts into a computer. The screen displays your message (output), and when you're done, you hit print, and the printer produces a hard copy of your letter. This interaction showcases how human-readable devices help us move from thoughts to a tangible form.

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.

Machine-readable devices are utilized by computers to perform tasks without user intervention. For example, a hard disk stores data that can be read by the system. To access that data, it might require passing through a series of machine-readable interfaces. These devices often handle the behind-the-scenes work, monitoring and controlling tasks like security, such as password entry or fingerprint recognition, ensuring that only authorized users can access certain system functionalities.

Think of a security system in a building. You can enter a password or scan your fingerprint, and once validated, the system allows you access. Here, the password and fingerprint scanners are examples of machine-readable devices – they confirm your identity to grant you access to secure areas, just like a computer uses such devices to decide if you can work on it.

So, this is the memory hierarchy and I think now, after going through this particular course...

In a computer system, memory is organized in a hierarchy based on speed, cost, and size. At the top of the hierarchy are registers, which are the fastest but smallest storage spaces within a processor. Below that is cache memory, which is faster than main memory and holds frequently accessed data. Main memory (RAM) comes next, being much larger but slower than cache. Finally, hard disks serve as long-term storage, being the largest in size but the slowest in access speed. This hierarchy ensures that the processor operates efficiently by storing data at different levels according to the speed with which the data is needed.

Consider a library. The fastest access (like registers) is the librarian’s desk where new books come in – they are readily available. Next is the popular section where commonly borrowed books (like cache) are kept for easier access. The main collection takes more time to access, as you need to walk to the stacks. The basement archives (like hard disks) hold a lot of books that you rarely need, so accessing them takes significant time. This approach keeps the library organized and responsive to user needs.

Now, what are the I/O module functions, already I have explained many more things...

The I/O module serves as an intermediary between the CPU and external devices, performing several critical functions such as control and timing, facilitating communication with the CPU and devices, managing data buffering to ensure smooth data transfers, and detecting errors during data transmission. Given that devices operate at different speeds compared to processors, the I/O module must buffer the data, ensuring efficient processing and preventing delays.

Imagine a chef (the CPU) in a busy restaurant kitchen that is preparing meals (data). The waiter (I/O module) takes orders (input) from customers and communicates them to the chef. However, the chef can only process so many dishes at once, so the waiter keeps track of pending orders and delivers them to the customers at the right time. This ensures that the chef can work efficiently without being overwhelmed at once, similar to how an I/O module buffers data for the CPU.

So, now, you just see that when I am explaining it, it is coming in a flow...

The I/O steps outline the sequence of operations from the moment the CPU wants to interact with I/O devices. The CPU first checks the status of the I/O module to confirm if the device is ready. If ready, it sends a command to either read from or write data to the device. The I/O module then retrieves the information from the device, buffers it, and finally transfers it to the CPU, or vice versa in case of output operations.

Think of ordering food at a restaurant. First, you ask the waiter (CPU) if a particular dish is available (checking status). Once confirmed, you place your order (sending command). The waiter then retrieves your order from the kitchen (I/O module gets data) and brings it to your table. This flow ensures that each step is handled in sequence, just as data is prepared and processed in computer operations.

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