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Computer memory and Types -primary vs secondary memory

                           Computer Memory

Computer memory is a physical device used to store information same as human brain. The memory stores the information in the form of '0' and '1'. These are called binary digits. It uses thousands of registers to store information. Although memory is technically any form of electronic storage, it is used most often to identify fast, temporary forms of storage. If your computer's CPU had to constantly access the hard drive to retrieve every piece of data it needs, it would operate very slowly. When the information is kept in memory, the CPU can access it much more quickly The memory is divided into large number of small parts called cells. Each location or cell has a unique address, which varies from zero to memory size minus one. For example, if the computer has 64k words, then this memory unit has 64 * 1024 = 65536 memory locations. The address of these locations varies from 0 to 65535.

 Types of computer memory
  1. Primary Memory 
  • RAM
  • ROM
      2. Secondary Memory
  • Hard disk
  • SSD
  • Pendrive
  • CD/DVD & BD
  • Data Card
  • Cloud Storage

Primary Memory :

Primary memory is the main memory of the computer system. Accessing data from primary memory is faster because it is an internal memory of the computer. The primary memory is most volatile which means data in primary memory does not exist if it is not saved when a power failure occurs.

The primary memory is a semiconductor memory. It is costlier compared with secondary memory. The capacity of primary memory is very much limited and is always smaller compares to secondary memory.

Two types of Primary Memory are:

  • RAM
  • ROM

RAM (Random Access Memory)

Random access memory which is also known as RAM is generally known as a main memory of the computer system. It is called temporary memory or cache memory. The information stored in this type of memory is lost when the power supply to the PC or laptop is switched off.

ROM (Read Only Memory)

It stands for Read Only Memory. ROM is a permanent type of memory. Its content is not lost when the power supply is switched off. The computer manufacturer decides the information of ROM, and it is permanently stored at the time of manufacturing which can not be overwritten by the user.

Characteristic of Primary Memory

  • The computer can't run without primary memory
  • It is known as the main memory.
  • You can lose data in case power is switched off
  • It is also known as volatile memory
  • It is a working memory of the computer.
  • Primary memory is faster compares to secondary memory.

What is Secondary Memory?

All secondary storage devices which are capable of storing high volume data is referred to secondary memory. It's slower than primary memory. However, it can save a substantial amount of data, in the range of gigabytes to terabytes. This memory is also called backup storage or mass storage media.

Hard Disk

Hard disk drive (HHD) : Hard Disk is fixed inside the CPU box. While working in a program, the CPU uses RAM for processing. when we save the file. it is copied from RAM to the hard disk. we can also save it on any other secondary devices.

Hard disk are of two types :

  1. Internal hard disk - Storage capacity 1TB to 16TB
  2. External Hard Disk- Storage Capacity as needed by user.

SSD (Solid State Drive)

Solid State Drive (SSD) : SSD is similar to a hard disk drive. It can access data faster than HDD.It is costlier.
SSD are of two types :
  1. Internal SSD - Storage Capacity 128GB to 2TB
  2. External SSD

Pen Drive

Pen Drive : A pen drive is a small portable secondary storage device used to store information permanently. It is called a flash drive.It is so small that it can be carried in a pocket.

CD, DVD & BD


 COMPACT DISK
 DIGITAL VERSATILE DISK
 BLUE RAY DISK
It can store data permanently.
It can store data permanently.It can store data permanently.
Can be carried easily.
Can be carried easily.Can be carried easily.
Storage Capacity upto    700MB
Storage Capacity -4.5GB      to 17GB
Single side disk upto 25GB
Double sided disk upto 50 GB

Data Card

Data Card : A data card is also a portable storage device. It is also known as a smart card. It is commonly used in cameras, MP3 players, tablets and mobile phones, etc.
Storage Capacity Upto 1 TB

Cloud Storage

Cloud Storage : Cloud storage means the data is stored on remote servers using the internet. You can store documents, pictures etc. from your computer and smart phones in the cloud storage. Google Drive, Dropbox, OneDrive are some of the commonly used cloud storage.
Storage Capacity -As per your data storage plan

Characteristic Secondary Memory

  • These are magnetic and optical memories
  • Secondary memory is known as a backup memory
  • It is a non-volatile type of memory
  • Data is stored permanently even when the power of the computer is switched off
  • It helps store data in a computer
  • The machine can run without secondary memory
  • Slower than primary memory

Primary Memory Vs Secondary Memory

Parameter          
 Primary memory Secondary memory
 Nature The primary memory is categorized as volatile & nonvolatile memories.                           The secondary memory is always a
 non-volatile memory.
 Alias  These memories are also called internal memory.  Secondary memory is known as a Backup memory or   Additional memory or Auxiliary memory.
 Access Data is directly accessed by the processing unit. Data cannot be accessed directly by the processor. It is first copied from secondary memory to primary memory. Only then CPU can access it.
 Formation It's a volatile memory meaning data cannot be retained in case of power failure.  It's a non-volatile memory so that that data can be retained even after power failure.
 Storage  It holds data or information that is currently being used by the processing unit. Capacity is usually in 16 to 32 GB  It stores a substantial amount of data and information. Capacity is generally from 200GB to terabytes.
 Accesses Primary memory can be accessed by the data bus. Secondary memory is accessed by I/O channels.
 Expense Primary memory is costlier than secondary memory. Secondary memory is cheaper than primary memory.

Summary

  • Computer memory is the storage space where data is to be processed, and instructions needed for processing are stored
  • Two types of memories are 1) Primary Memory, 2)Secondary Memory
  • Primary memory is the main memory of the computer system. Accessing data from primary memory is faster because it is an internal memory of the computer.
  • All secondary storage devices which are capable of storing high volume data is referred to as secondary memory
  • Types of Primary Memory 1) RAM, 2) ROM
  • Types of Secondary Memory 1) Hard Drive, 2) SSD, 3) Flash, 4) Optical Drive, 5) USD Drive, 3) Magnetic Tapes
  • The computer can't run without primary memory. You can lose data in case power is switched off
  • Data is stored permanently in Secondary Memory even when the power of the computer is switched off
  • Primary memory is expensive and is available in limited in size in a computer.
  • Secondary memory is cheaper compared to primary memory.

KEY DIFFERENCE

  • Primary memory is also called internal memory whereas Secondary memory is also known as a Backup memory or Auxiliary memory.
  • Primary memory can be accessed by the data bus whereas Secondary memory is accessed by I/O channels.
  • Primary memory data is directly accessed by the processing unit whereas Secondary memory data cannot be accessed directly by the processor.
  • Primary memory is costlier than secondary memory whereas Secondary memory is cheaper compared to primary memory.
  • Primary memory is both volatile & nonvolatile whereas Secondary memory is always a non-volatile memory.

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