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Introduction of Secondary Memory

Primary memory has limited storage capacity and is volatile. Secondary memory overcomes this limitation by providing permanent storage of data and in bulk quantity. Secondary memory is also termed external memory and refers to the various storage media on which a computer can store data and programs. The Secondary storage media can be fixed or removable. Fixed Storage media is an internal storage medium like a hard disk that is fixed inside the computer. A storage medium that is portable and can be taken outside the computer is termed removable storage media. 

Secondary memory is a type of computer memory that is used for long-term storage of data and programs. It is also known as auxiliary memory or external memory, and is distinct from primary memory, which is used for short-term storage of data and instructions that are currently being processed by the CPU.

Secondary memory devices are typically larger and slower than primary memory, but offer a much larger storage capacity. This makes them ideal for storing large files such as documents, images, videos, and other multimedia content.

Some examples of secondary memory devices include hard disk drives (HDDs), solid-state drives (SSDs), magnetic tapes, optical discs such as CDs and DVDs, and flash memory such as USB drives and memory cards. Each of these devices uses different technologies to store data, but they all share the common feature of being non-volatile, meaning that they can store data even when the computer is turned off.

Secondary memory devices are accessed by the CPU via input/output (I/O) operations, which involve transferring data between the device and primary memory. The speed of these operations is affected by factors such as the type of device, the size of the file being accessed, and the type of connection between the device and the computer.

Overall, secondary memory is an essential component of modern computing systems and plays a critical role in the storage and retrieval of data and programs.

Difference between Primary Memory and Secondary Memory: 

Primary Memory Secondary Memory
Primary memory is directly accessed by the Central Processing Unit(CPU). Secondary memory is not accessed directly by the Central Processing Unit(CPU). Instead, data accessed from a secondary memory is first loaded into Random Access Memory(RAM) and is then sent to the Processing Unit.
RAM provides a much faster-accessing speed to data than secondary memory. By loading software programs and required files into primary memory(RAM), computers can process data much more quickly. Secondary Memory is slower in data accessing. Typically primary memory is six times faster than secondary memory.
Primary memory, i.e. Random Access Memory(RAM) is volatile and gets completely erased when a computer is shut down. Secondary memory provides a feature of being non-volatile, which means it can hold on to its data with or without electrical power supply.

Uses of Secondary Media:  

Fixed and Removable Storage 

Fixed Storage- 
Fixed storage is an internal media device that is used by a computer system to store data, and usually, these are referred to as the Fixed disk drives or Hard Drives. 
Fixed storage devices are literally not fixed, obviously, these can be removed from the system for repairing work, maintenance purposes, and also for an upgrade, etc. But in general, this can’t be done without a proper toolkit to open up the computer system to provide physical access, and that needs to be done by an engineer. 
Technically, almost all of the data i.e. being processed on a computer system is stored on some type of a built-in fixed storage device. 

Types of fixed storage:  

Removable Storage- 
Removable storage is an external media device that is used by a computer system to store data, and usually, these are referred to as the Removable Disks drives or the External Drives. 
Removable storage is any type of storage device that can be removed/ejected from a computer system while the system is running. Examples of external devices include CDs, DVDs, and Blu-ray disk drives, as well as diskettes and USB drives. Removable storage makes it easier for a user to transfer data from one computer system to another. 
In storage factors, the main benefit of removable disks is that they can provide the fast data transfer rates associated with storage area networks (SANs) 

Types of Removable Storage:  

Secondary Storage Media 

There are the following main types of storage media: 

1. Magnetic storage media: 
Magnetic media is coated with a magnetic layer that is magnetized in clockwise or anticlockwise directions. When the disk moves, the head interprets the data stored at a specific location in binary 1s and 0s at reading. 

Examples: hard disks, floppy disks, and magnetic tapes.

2. Optical storage media 
In optical storage, media information is stored and read using a laser beam. The data is stored as a spiral pattern of pits and ridges denoting binary 0 and binary 1. 
Examples: CDs and DVDs

CD- ROM CD-R CD-RW
It stands for Compact Disk – Read Only Memory It stands for Compact Disk- Recordable. It stands for Compact Disk-Rewritable.
Data is written on these disks at the time of manufacture. This data cannot be changed, once is it written by the manufacturer, but can only be read. CD- ROMs are used for text, audio and video distribution like games, encyclopedias, and application software. Data can be recorded on these disks but only once. Once the data is written in a CD-R, it cannot be erased/modified. It can be read or written multiple times but a CD-RW drive needs to be installed on your computer before editing a CD-RW.

3. Solid State Memories 
Solid-state storage devices are based on electronic circuits with no moving parts like the reels of tape, spinning discs, etc. Solid-state storage devices use special memories called flash memory to store data. A solid state drive (or flash memory) is used mainly in digital cameras, pen drives, or USB flash drives. 

Pen Drives: 
Pen Drives or Thumb drives or Flash drives are the recently emerged portable storage media. It is an EEPROM-based flash memory that can be repeatedly erased and written using electric signals. This memory is accompanied by a USB connector which enables the pen drive to connect to the computer. They have a capacity smaller than a hard disk but greater than a CD. Pendrive has the following advantages: 

Here are some advantages and disadvantages of secondary memory:

Advantages:

  1. Large storage capacity: Secondary memory devices typically have a much larger storage capacity than primary memory, allowing users to store large amounts of data and programs.
  2. Non-volatile storage: Data stored on secondary memory devices is typically non-volatile, meaning it can be retained even when the computer is turned off.
  3. Portability: Many secondary memory devices are portable, making it easy to transfer data between computers or devices.
  4. Cost-effective: Secondary memory devices are generally more cost-effective than primary memory.

Disadvantages:

  1. Slower access times: Accessing data from secondary memory devices typically takes longer than accessing data from primary memory.
  2. Mechanical failures: Some types of secondary memory devices, such as hard disk drives, are prone to mechanical failures that can result in data loss.
  3. Limited lifespan: Secondary memory devices have a limited lifespan, and can only withstand a certain number of read and write cycles before they fail.
  4. Data corruption: Data stored on secondary memory devices can become corrupted due to factors such as electromagnetic interference, viruses, or physical damage.
  5. Overall, secondary memory is an essential component of modern computing systems, but it also has its limitations and drawbacks. The choice of a particular secondary memory device depends on the user’s specific needs and requirements.
     

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