Primary memory
Table of Content:
There are two types of computer memory:
1. Primary memory
It is accessible directly by the processing unit. e.g., RAM
As soon as the computer is switched off, contents of the primary memory is lost. Data can be stored and retrieved much faster with primary memory compared to secondary memory.
Primary memory in the computer is in the form of IC’s (Integrated Circuits). These circuits are called Random Access Memory (RAM). Each of RAM’s locations stores one byte of information. (One byte is equal to 8 bits). A bit is an acronym for binary digit, which stands for one binary piece of information. This can be either 0 or 1.
Primary or internal storage section is made up of several small storage locations (ICs) called cells. Each of these cells can store a fixed number of bits called word length.
Capacity of Primary memory.
As each cell of memory contains one character or 1 byte of data, so capacity is defined in terms of byte or words.
e.g., 64 kilobyte (KB) memory is capable of storing 64 * 1024 = 65536 bytes. (1 kilobyte is 1024 bytes).
A memory size ranges from few kilobytes in small systems to several thousand kilobytes in large mainframe and super computer. In personal computer, we find memory capacity in the range of 64 KB, 4 MB, 8 MB and even 16 MB (MB = Million bytes).
2. Secondary memory
This memory stores much larger amounts of data and information for extended periods of time. Data in secondary memory cannot be processed directly by the CPU, it must first be copied into primary memory, i.e. RAM. It is the slower and cheaper form of memory. Secondary storage is used to store data and programs when they are not being processed. It is also non-volatile in nature. Due to this, the data remain in the secondary storage as long as it is not overwritten or deleted by the user. It is a permanent storage. It is located outside the computer.
Note : Primary memory is more expensive than secondary memory and because of this, size of primary memory is less than that of secondary memory.
Secondary memory devices include as follows:
Magnetic Storage, Optical Storage, Solid State Storage