Memory of the Computer:

• The memory of the computer is measured in units of bits and bytes.
• The full form of bit is Binary Digit.
• It is the smallest unit of memory.
• It can have a single numeric value of 0 or 1.

  

  (Byte Chart)

Memory of the Computer

Primary/ Main Memory:

• The primary memory is a part of the Central Processing Unit or CPU.
• It is also called the main memory of the internal memory.
• The primary memory is fixed up on the motherboard inside the CPU.

RAM (Random Access Memory):

• RAM is employed to store data and directions that are currently being processed by a computer’s CPU.
• It is also referred to as Read and Write Memory.
• We can read and write data onto it.
• The data stored in RAM is temporary and disappears when a program is closed or the pc is pack up .
• RAM of a computer is measured in gigabytes (GB).

ROM (Read Only Memory):

• ROM is the permanent memory of a computer.
• ROM can only be read. It cannot be write.
• ROM stores instructions for the working of the pc system.
• These instructions have written at the manufacturing time.

Secondary Memory:

Hard Disk:

Hard disk drive is formed from a series of circular disks called platters arranged one over the opposite almost ½ inches apart around a spindle. Disks are made of non-magnetic material like aluminum alloy and coated with 10-20 nm of magnetic material.Capacity in terabytes (TB).

CD stands for Compact Disk.

• DVD- Digital Versatile Disc or Digital Video Disc
• CDs are circle shape disks that use optical rays, usually lasers, to read and write data. 
• They are rock bottom as you'll get 700 MB of space for storing for fewer than a dollar.
• CDs are inserted in CD drives tray into CPU box.
• They are portable as we can eject the drive, remove the CD and carry it with us.

(Types of CDs)

CD-ROM (Compact Disk – Read Only Memory).

• The data on these CDs are recorded by the manufacturer.
• Audio or video are released on CD-ROMs.

CD-R (Compact Disk – Recordable).

• Data are often written by the user once on the CD-R.
• It cannot be deleted or modified later. 

CD-RW (Compact Disk – Rewritable).

• Data are often written and deleted on these optical disks again and again.

Pen Drive:

• Pen drive may be a portable storage device that uses solid state memory instead of magnetic fields or lasers to record data.
• It is also called USB drive, key drive or non-volatile storage .

External Hard Disk:

• An external disk drive may be a portable memory device which will be attached to a computer through a USB or wirelessly.
• External hard drives typically have high storage capacities and are often wont to copy computers.

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