Computer Memory and storage
Computer Memory and storage
The storage unit of a computer system holds (or stores) the following :
- Data and instructions required for processing (received from input devices)
- Intermediate results of processing
- Final results of processing, before they are released to an output device
Types of Memory
- Cache Memory
- Primary Memory
- Secondary Memory
- Used to hold running program instructions
- Used to hold data, intermediate results, and results of ongoing processing of job(s)
- Fast in operation
- Small Capacity
- Volatile (looses data on power dissipation)
- Used to hold stored program instructions
- Used to hold data and information of stored jobs
- Slower than primary storage
- Large Capacity
- Lot cheaper that primary storage
- Retains data even without power
- These are semiconductor memories.
- It is known as the main memory.
- Usually volatile memory.
- Data is lost in case power is switched off.
- It is the working memory of the computer.
- Faster than secondary memories.
- A computer cannot run without the primary memory.
This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently. CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. For example, disk, CD-ROM, DVD, etc.
Compact Disk: A Compact Disc drive(CDD) is a device that a computer uses to read data that is encoded digitally on a compact disc(CD). A CD drive can be installed inside a computer’s compartment, provided with an opening for easier disc tray access or it can be used by a peripheral device connected to one of the ports provided in the computer system.A compact disk or CD can store approximately 650 to 700 megabytes of data.
DVD: It stands for Digital Versatile Disk or Digital Video Disk. It looks just like a CD and use a similar technology as that of the CDs but allows tracks to be spaced closely enough to store data that is more than six times the CD’s capacity. It is a significant advancement in portable storage technology. A DVD holds 4.7 GB to 17 GB of data.
Blue Ray Disk: This is the latest optical storage media to store high definition audio and video. It is similar to a CD or DVD but can store up to 27 GB of data on a single layer disk and up to 54 GB of data on a dual layer disk. While CDs or DVDs use red laser beam, the blue ray disk uses a blue laser to read/write data on a disk.
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. 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 which can be repeatedly erased and written
using electric signals. This memory is accompanied with a USB connector which enables the
pendrive to connect to the computer. They have a capacity smaller than a hard disk but greater
than a CD