20.2.1. Types of Memory

Basically, if you look memories are divided into mainly two types: internal memory and external memory.

Memory in computer systems can be categorized into two main types: internal memory and external memory. Internal memory is the memory that is directly accessible by the CPU, which includes components located within the CPU or nearby. External memory, on the other hand, refers to storage that is not directly accessible by the CPU, like hard drives or USB drives.

Think of internal memory as your immediate workspace where you have everything you need at hand (like a desk), while external memory is akin to files stored in a drawer that you can access when needed. You have to open the drawer to get the files, which takes more time than grabbing something off your desk.

Internal memory basically is the semiconductor kind of a memory... which is called the register.

Internal memory is a type of semiconductor memory and includes registers, cache memory, and main memory (RAM). Registers are the smallest type of memory, located within the CPU itself, which are used to hold temporary data that the CPU is currently processing. Cache memory is faster than main memory and stores frequently used data to speed up processing.

Imagine registers as sticky notes on your desk that you use for quick calculations or reminders. Cache memory is like a small drawer of frequently needed tools that you can quickly access without searching through your entire toolbox (main memory).

Main memory is the word we have always heard the word called RAM.

Main memory, commonly referred to as RAM (Random Access Memory), is a type of volatile memory that temporarily stores data that the CPU needs while operating. Volatile means that data is lost when the power is turned off. RAM allows for quick read and write operations, making it crucial for performance during software execution.

Think of RAM as your short-term memory. You can quickly recall information, like what you need from the grocery store, but once you leave the store without writing it down (power off), that memory is gone. You need to save the important stuff onto a notepad (external memory) to remember later.

And there is something called the last or the most top level in the memory which is called the hard disk that is your external memory.

External memory, such as hard drives and SSDs, is used for long-term data storage. Unlike internal memory, it is non-volatile, meaning the data remains intact even when the computer is powered down. This is where all programs, files, and other data are permanently saved.

External memory is like your filing cabinet where you store important documents and files. You don't access it as quickly as your workspace (internal memory), but once you file something away, it stays there safely until you need it again.

So basically the main memory which is mainly we are concerned about... cache is transparent for our case and so forth.

The memory hierarchy in a computer system ranges from the fastest and smallest internal memory (registers) to slower but larger external memory (hard disks). This hierarchy is crucial for optimizing performance. As we go down the hierarchy, the speed decreases, but storage capacity increases.

Consider a layered cake: the top layer (registers) holds the most crucial and frequently used items, while the larger bottom layers (RAM and external memory) hold bulk items, easy to access but not always needed immediately. The trick is to balance between quick access and total storage.

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