30.2.1. Objective 1: Identify the storage devices for secondary memory

We know that computer works on Von Neumann stored program principle and processor is going to work with the data available in the main memory. So, main memory is a semiconductor memory or semiconductor device. Again we know that it is volatile in nature. So, once we switch off the machine information will simply go from the memory, so we need some permanent storage devices.

This chunk introduces the need for secondary memory in computer systems. Main memory, also known as RAM (Random Access Memory), temporarily stores data that the CPU needs while the machine is powered on. However, this memory type is volatile, meaning that all stored information is lost when the computer is turned off. This indicates the necessity for a more permanent form of storage to save data long-term.

Think of main memory like a chalkboard – it holds information while you are using it, but as soon as the class ends and the board is wiped clean, all notes are lost. On the other hand, secondary memory is like a notebook where you write down important notes; even if you close the notebook, the information remains there for future reference.

Secondly, we know that in main memory we are having a limited capacity; it may be either 2 GB or 4 GB, in the current scenario it was very less.

This chunk explains the limitation of main memory in terms of capacity. Modern computers usually have a specific amount of RAM, which can support only a limited amount of applications and data simultaneously. Given that contemporary applications and operating systems require more space, the limited capacity of RAM makes it insufficient to store everything needed for effective performance.

Consider main memory as a small suitcase that holds only a few clothes. If you try to pack too many clothes (or applications and data), you won’t be able to close the suitcase. Secondary memory, on the other hand, is like a full wardrobe where you can store as many clothes as you want. You can pack and retrieve what you need whenever required.

So, one of the most common secondary storage devices is your hard disk. So, in this particular lecture we are going to briefly explain about the hard disk.

In this chunk, the hard disk is introduced as a primary example of secondary storage. Hard disks provide a larger capacity for data storage compared to main memory, ensuring that data can be saved permanently even when the computer is powered off. Other types of secondary storage devices, like CDs, DVDs, and magnetic tapes, are also recognized for their unique purposes, including backups and data archiving.

If main memory represents a cupboard where you only keep the clothes you are currently wearing, the hard disk is akin to a storage basement where you can store old clothes and seasonal items. You may not use these items every day, but they are kept safe for when you need them in the future.

If you look into the memory hierarchy, so, in this case we are going to say that in the in board memory; that means, maybe it is inside the processor or it may be in a motherboard, because all indicated component of a processor or that computer will be put in a board and you say this is the motherboard.

This chunk discusses the concept of memory hierarchy, where different types of storage (such as registers, cache, main memory, and secondary memory) are organized based on speed, capacity, and cost. At the top are fast, small capacity memories like registers, followed by cache, then main memory, and lastly secondary storage devices like hard disks which are slower but can store much more data.

Think of memory hierarchy like a kitchen. The chef (CPU) has immediate access to the kitchen counter (registers) for tools like knives (fast but limited). The fridge (cache) holds frequently used ingredients (faster access), while the pantry (main memory) stores a wider variety (a lot of space). Finally, the basement (secondary memory) has bulk supplies that are infrequently accessed, like extra rice and canned goods.

Just I am mentioning over here it is we are having a disk substrate coated with magnetic materials. So, basically in most of the cases you will find that this is some sort of your circular plate and the surface of this player will be coated with magnetisable material.

Here, the basic structure and working of a hard disk are described. A hard disk consists of a circular platter coated with magnetic material where data is stored. The disk rotary action, combined with the read/write head, allows the system to access or write information on the coating. The way this information is written and read using magnetic fields is key to the operation of hard disks.

Imagine writing notes with a special pen that leaves invisible ink (the magnetic material). As you rotate the paper (disk), you can all of a sudden see the notes when shone under UV light (read/write mechanism). This highlights how data can be stored, retrieved, and organized in a different, permanent format.

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