The document discusses different types of computer memory including primary memory like RAM and ROM, and secondary memory like magnetic disks, magnetic drums, CD-ROMs, and hard disks. It defines a hard disk drive as using rapidly rotating disks coated with magnetic material to store and retrieve digital data in a random-access manner. The document also covers optical discs which encode data in the form of pits and lands on a circular disc, and defines common units of data storage like kilobytes, megabytes, and terabytes in terms of bytes.

2. Arithmetic logic unit
Control unit
Memory unit

3. 
Memory Unit
Primary memory Secondary memory
RAM- Random Access Memory
ROM- Read only memory
Magnetic disk
Magnetic drum
CD-ROM
HARD DISK

5. 
•Secondary storage also know as external memory not
directly accessible by the CPU.
Secondary memory is where programs and data are kept on a
long-term basis.
This section of the memory is also referred to as backup
storage.
•The storage capacity of primary storage is not sufficient to
store the large volume so secondary storage.
`Introduction

6.  A hard disk drive (HDD), hard disk,
hard drive, or fixed disk is an electro-
mechanical data storage device that
uses magnetic storage to store and
retrieve digital information using one
or more rigid rapidly rotating disks
(platters) coated with magnetic
material. The platters are paired with
magnetic heads, usually arranged on a
moving actuator arm, which read and
write data to the platter surfaces. Data
is accessed in a random-access manner,
meaning that individual blocks of data
can be stored or retrieved in any order
and not only sequentially. HDDs are a
type of non-volatile storage, retaining
stored data even when powered off.
Hard Disk

7. 
In computing and
optical disc
recording
technologies, an
optical disc is a flat,
usually circular disc
which encodes
binary data in the
Optical disc

8.  Nibble. A nibble is 4 bits.
 Byte. Today, a byte is 8 bits.
 Kilobyte (KB) A kilobyte is 1,024 bytes.
 Megabyte (MB) A megabyte is 1,048,576 bytes
 Gigabyte (GB) A gigabyte is 1,073,741,824 (230) bytes. ...
 Terabyte (TB) ... 1,099,511,627,776. (240) bytes
 Petabyte (PB) ... 1,125,899,906,842,624 . (250) bytes
 Exabyte (EB)….. 1,152,921,504,606,846,976. (260) bytes
 Zettabyte (ZB)…1,180,591,620,717,411,303,424. (270) bytes
 Yottabyte (YB)…. 1,208,925,819,614,629,174,706,176 (280)
bytes
Calculate of bits
(2)^(n)