32.3.1. External Memory Explanation

So, now that is all about the working principle of hard disk and just we are discussing in a nutshell, how it works? And how we are going to store information? And how we are going to organize the information?

In this chunk, the basic concept of external memory is introduced, relating directly to how data is stored and organized. External memory refers to storage devices that hold data permanently, unlike main memory (RAM), which is volatile. The hard disk is identified as a prime example of such external memory.

Think of external memory as a filing cabinet (the hard disk) where you store important documents (data). Unlike the desk (main memory) where you work temporarily and can lose things, the filing cabinet keeps everything safe until you need to access it again.

What is external memory and why it is required? How external memory is generally implemented? So, this is basically test the time to meet the objective one, already I have mentioned that that main memory is volatile in nature to permanent storage we need this particular external memory.

External memory is essential for long-term data storage since the main memory used in computers (like RAM) loses data when power is off. This section emphasizes the need for permanent storage solutions such as hard disks, which utilize various technologies like magnetic or optical methods for data retention.

Imagine if your computer was like a whiteboard where you write your notes. Every time you wipe it down, all your notes are lost (like in RAM). An external memory device is like a notebook where you can write your notes for future reference without losing them every time the board is cleaned.

Now, question 2, explain the basic working principle of a hard disk. If you are talking about hard disk basically I am mentioning about the magnetic disk. So, this is the design principle I am asking, so working principle already we have discussed about the design issues of hard disk.

This chunk discusses the fundamental operation of a hard disk, highlighting it as a magnetic disk device. It involves writing and reading data by using magnetic signals that the hard disk converts into electrical signals and vice versa. The key components include the hard disk controller and device drivers to facilitate data transfer.

The hard disk works similarly to a vinyl record player. The needle reads the grooves (data) on the record (disk) to playback music (retrieve information). If the needle doesn’t function properly (like the controller not working), you won't hear the music.

Now question number 3 how is data organized and accessed in a magnetic disk? I think we have explained it. It is a sector, track, and surface.

Data on a magnetic disk is organized in sectors, tracks, and surfaces. Each track on the disk contains multiple sectors, which are the smallest unit of storage. This organization allows efficient storage and retrieval of data. As the head moves across these tracks and sectors, it is essential for fast access times.

Imagine a library where books are organized on shelves (surfaces), each shelf has rows of books (tracks), and each book (sector) contains pages of information. For efficient searching, a librarian uses this structured way to know exactly where each topic is located.

Explain how is the performance of a magnetic disk measured? So, this depends on the data transfer. How to measure the capacity of a hard disk? So, again you just see how we are going to measure a capacity of a hard disk; we know the number of track, number of sector, number of surface and the block size depending on these things we can calculate the capacity of the hard disk.

The performance of a magnetic disk is primarily measured by data transfer rates, seek time, and rotational delay. For example, the speed at which the read/write head can move to the designated track (seek time) directly influences the overall performance in reading or writing data.

Think of performance as how quickly a chef can prepare a meal. The chef must move efficiently to gather ingredients (seek time) and cook them as fast as possible (data transfer rate). Just as a chef's prep time affects meal serving, a hard disk's speed impacts data access time.

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