RAM or Random Access Memory – Primary memory

After having understood about CPU let’s talk about the next important hardware component present in the computer – the RAM or Random Access Memory

As discussed in the previous tutorial the role of the CPU is to process data and instructions. But from where does the CPU get the data and instructions which it needs to process. This is where the RAM comes into picture. The CPU picks up the instructions and data from the RAM and processes them. This is why RAM is called the primary memory, because the CPU directly interacts with the RAM.

This is how a RAM looks like in real


Meaning of Random Access Memory

The name random access memory comes from the way the RAM is designed. Below is a conceptual design of the RAM


As you can see that conceptually the RAM looks like a large rectangle which is further divided into small rectangles of same length and breadth. Each internal rectangle is a single block of memory with size 1 byte and is assigned a numeric address. The addresses start from 0 and go up till 2^n – 1 where n is the number of bits in the CPU. A 32 bit CPU can have a RAM of size 2^32 – 1 and a 64 bit CPU can have a RAM of size 2^64 – 1. So larger the bit size of a CPU the more RAM it can have.

This memory is called random access because you can randomly access data from any memory location in the RAM if you know the address of that memory location. You do not have to sequentially move from one location to another to read the data from inside the RAM. If it would have required moving in a sequential manner then this hardware would have been called SAM or Sequential Access Memory.

As you can notice from the diagram a byte is the smallest addressable unit of memory inside the RAM. In simple words you can say that RAM is divided into memory blocks of size 1 byte each and every block is assigned a unique numeric address starting from 0.  

As a programmer it is very important for you to understand the conceptual model of the RAM. When you start learning about programming in coming E-Classrooms we will talk about the logical division of RAM into different segments in order to logically store different parts of a program into different segments.

RAM is temporary memory

Another important point to keep in mind about RAM is that it is a temporary memory storage also known as volatile memory. It is called temporary storage because the data and instructions stored in the RAM are lost if the power supply to the computer is cut off. RAM remembers its contents only till the computer is on. Once it is turned off all the data is lost.

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