Main memory is the internal storage area in a computer that temporarily stores data and programs. It includes RAM and ROM and allows for quick access of data by the CPU. Secondary memory provides long-term storage of data and programs not currently in use, such as on hard disks, CDs, DVDs, and USB drives. Computer memory is measured in bits, bytes, kilobytes, megabytes, gigabytes, and terabytes, with each unit being a multiple of the previous unit by a factor of 1024.

2. What is Main Memory?
• Main Memory is an internal storage area in a
computer, which is availed to store data and
programs either permanently or temporarily.
• Computer memory is any physical device capable
of storing information temporarily, like RAM
(random access memory), or permanently, like
ROM (read-only memory).
• Memory devices utilize integrated circuits and are
used by operating systems, software, and
hardware.

4. Why is memory important or needed for a
computer?
• Each device in a
computer operates at
different speeds and
computer memory gives
your computer a place to
quickly access data.
• If the CPU had to wait for
a secondary storage
device, like a hard disk
drive, a computer would
be much slower.

5. Types of Computer Memory
• Computer memory is broadly divided into two
groups and they are:
1. Primary memory
2. Secondary memory
• When the main memory holds instructions and
data when a program is executing, the auxiliary
memory or secondary memory holds data and
programs which are not currently in use and
furnishes long term storage.

6. Types of Computer Memory

7. 1. Primary Memory
• This is the main memory of the computer. CPU can
directly read or write on this memory. It is fixed on
the motherboard of the computer.
• Primary memory is the only type of memory which
is directly accessed by the CPU. The CPU
continuously reads instructions stored in the
primary memory and executes them.
• Any data that has to be operated by the CPU is also
stored. The information is transferred to various
locations through the BUS.

8. 1. Primary Memory
• Primary memories are
of two types.
They are:
i. RAM (Random Access
Memory)
ii. ROM (Read Only
Memory)

10. 2. Secondary Memory
• Secondary memory or auxiliary memory consists
of slower and less expensive device that
communicates indirectly with CPU via main
memory.
• The secondary memory stores the data and keeps
it even when the power fails. It is used to store or
save large data or programs or other information.
• This memory is permanent in nature. It is used to
store the different programs and the information
permanently (which were temporarily stored in
RAM). It holds the information till we erase it.

11. 2. Secondary Memory
• Different types of secondary storage devices are:
Hard Disc Compact Disc
DVD Pen Drive
Flash Drive Magnetic disks
Magnetic tape Optical disk
Mass storage devices USB

13. Memory Units
• Data in the computer’s memory is represented by the
two digits 0 and 1. These two digits are called Binary
Digits or Bits. A bit is the smallest unit of computer’s
memory.
i. Bits = 0,1
ii. 1 nibble = 4 bits
iii. 1 Byte = 8 bits (e.g,11001011)
iv. 1 KB(kilobyte) = 1024 Bytes
v. 1 MB(megabyte) = 1024 KB
vi. 1 GB(Gigabyte) = 1024 MB
vii. 1 TB(Terabyte) = 1024 GB

14. Memory Units