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Functions of Memory


Objective:

On completion of this period, you would be able to learn

Functions of memory.

Types of memory.


Recap

Blocks in CPU

Control unit & Arithmetic and Logical Unit.

Functions of CPU

Performs calculations, takes decisions, and controls all the units.


Prerequisites:

What is a memory?

Memory is a device that stores computer’s data & programs.


Memory hierarchies

Registers PrimaryMemory

SecondaryMemory


Memory (Contd..)

A space to keep computer’s data.

It stores program, data results or any kind of information.

Memory stores binary information i.e. 0’s and 1’s.


Memory (contd)

Place where results get stored prior to the output Memory is measured in bytes One byte of memory is needed to store a

character


Units of measure for computer memory

Unit Abbrevia-tion

ApproximateValue (Bytes)

Actual Value(Bytes)

Kilobyte KB 1,000 1,024

Megabyte MB 1,000,000(1 million)

1,048,576

Gigabyte GB 1,000,000,000(1 billion)

1,073,741,824

Terabyte TB 1,000,000,000,000(1 trillion)

1,099,511,627,776


Types of memory

MEMORYMEMORY

PRIMARY MEMORY(INTERNAL MEMORY)

PRIMARY MEMORY(INTERNAL MEMORY)

SECONDARY MEMORY(EXTERNAL MEMORY)

SECONDARY MEMORY(EXTERNAL MEMORY)

CPUCPU

REGISTERREGISTER ON CHIPCACHE

ON CHIPCACHE

MAGNETICTAPE

MAGNETICTAPE MAGNETIC

DISK

MAGNETICDISK

OPTICALDISK

OPTICALDISK

RAMRAM ROMROM

DRAMDRAMSRAMSRAM PROMPROM EPROMEPROM

EEPROMEEPROM


Random Access Memory (RAM)

It is volatile memory i.e. temporary memory.

Performs read and write operations.

Usually hidden to users.


RAM (Contd..)

It exists as a chip on the motherboard near the CPU.

RAM stores data and programs while they are being used.


Random Access Memory


Types of RAM

1. DRAM (Dynamic RAM)

2. SRAM (Static RAM)


Dynamic RAM

Dynamic RAM loses its stored information in a very short time even though the power supply is on.

Only one transistor is needed to form a memory cell and result in high packing density and moderate speed.


Dynamic RAM (Contd...)

Consume less power.

Used where large capacity of memory is needed.

Dynamic RAM being cheaper is used for main memory.


Static RAM

Static RAM retain stored information only as long as power supply is on.

Static RAMs are costlier and consume more power.

Static RAM being faster is used in cache memory.

Static RAMs hold information in flip-flop consisting of two cross coupled inverters.


Read Only Memory (ROM)

It is non volatile memory .i.e. permanent storage.

Performs only read operations.

Hidden to users.

used to store routine & fixed programs, during the booting process.


Types of ROM

1. PROM - (Programmable Read Only Memory)

2. EPROM - (Erasable Programmable Read Only Memory)

3. EEPROM - (Electrically Erasable PROM)


Cache memory

Placed between the CPU and the main memory.

It increases the speed of the computer up to 15%.


Cache memory (contd)

It is not accessible to users i.e. information cannot be written into cache memory by users.

It stores instructions and data which are to be immediately executed.


Primary memory

The storage is temporary.

Data stored in it lost when power supply is cut off.

Storage capacity is limited.


Primary memory (contd)

Known as Main Memory or Internal Memory

It is a part of CPU

Used for storing a little volume of data at the time of processing


Secondary memory

The storage is permanent.

The data stored in it does not get erased when the power is switched off.


Secondary memory (contd)

Known as External Memory or Auxiliary Memory

Storage capacity is unlimited

Used to store large volumes of data permanently


Secondary Memory - Examples

Magnetic tape

Magnetic disk

Optical disk


Summary:

In this class, we have learnt about

Functions of memory.

Types of memory used in computers.


Questions

Explain the types of memory devices used?

List the differences between RAM & ROM.

Explain the functions of memory?


Quiz:

1. Is RAM a volatile memory?

a. Yes

b. No

Answer: a


Quiz:

2. ROM is a

a. Volatile

b. Non-volatile

c. both a & c

Answer: b


Quiz:

3. The data stored in memory is in

a. Decimal form

b. Hexadecimal form

c. Binary form

d. Octal form

Answer: c

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