SS2 ICT NOTE

TOPIC: Scheme of work

WEEK[S] TOPICS 1
Revision 2-3 Communication
System 4 Central Processing Unit
5-6 Memory Unit
7 Logic Unit II 8
Presentation Package 9-10 Algorithm
and Flowchart

WEEK 2-3
COMMUNICATION SYSTEM
Communication is the field of study concerned with the transmission of information through various means. ICT stands fo
Information and Commmunication Technology which is a technology that provides access to information through
telecommunication.

TYPES OF ICT
1. Broadcasting: The broadcasting is a method of transferring the message to all recipients simultaneously. It can
also be referred to as the distributor of audio and video content to a dispersed audience through a medium such as
television, radio and satellite.

TYPES OF BROADCASTING
a. Radio Broadcasting: This is a one-way sound broadcasting service, transmitted over radio waves from a
transmitted to a receiver, antenna and intended to reach a wide audience.
b. Television Broadcasting: This is also known as telecast. It is the distribution of audio and/or video signals whi
transmit programs to audience.
c. Satellite Television System: It is a television service by means of communication satellite and received by a satelli
dish and set top box.

2. Telecommunication: It is the exchange of information over significant distance using electronic medium
such as telephone, cables and telegraph.

TYPES OF TELECOMMUNICATION
a. PSTN [Public Switched Telephone Network]
b. GSM [Global System for Mobile Communication]
c. CSPTS [Circuit Switch Packet Telephone System]
d. STS [Satellite Telephone System]
e. FWTS [Fixed Wireless Telephone System]
3. Data Network: It is an electronic communication process that allows for the orderly transmission and
reception of data such as letters, documents, etc.

TYPES OF DATA NETWORK

a. PAN (Personal Area Network): It is a computer network organized around an individual or a person. It involves
computer, a cell phone and other personal computing devices.
b. LAN (Local Area Network): It is a group of computers and associated devices that share a common
communication line or wireless link e.g within a school.
c. WAN (Wide Area Network): This is a network that covers several cities, states and even countries.
d. MAN (Metropolitan Area Network): It is a computer network that covers a metropolis such as city, campus, etc

4. Information System: It is the collection of components such as people, procedures, data, database,
telecommunication system, software and hardware that are used together and analyzed digital information.

TYPES OF INFORMATION SYSTEM

1. Data Processing: The data processing is also known as transaction processing system. They are used to process
data in firms and organizations that are not online.
2. GPS (Global Positioning System): This is a global information system that uses satellites to transmit signal
information to the Earth via GPS receiver.

WEEK 4
CENTRAL PROCESSING UNIT (CPU)
The Central Processing Unit (CPU) is a portion of the computer system that executes the instructions of a computer progra
and it is the primary element carrying out the function of the computer. It is also referred to as the processor or the brain
the heart of the computer system. It can be found in the motherboard.

COMPONENTS OF THE CPU

1. Arithmetic and Logic Unit (ALU)
2. Control Unit
1. Arithmetic and Logic Unit (ALU): The arithmetic and logic unit is the digital circuit that performs arithmetic and
logic unit operation. E.g addition, subtraction, multiplication, division, logic AND, OR, NOT, Greater than (>), Less than (<
=>, =<, etc.
2. Control Unit: The contol unit is an important component of the CPU which acts like a supervisor of the compu
that controls and co-ordinates all activities of the computer system.
The control unit performs the following basic functions or instructions:
i. It fetches instruction from the main memory
ii. It decodes the instruction i.e it interprets the instructions that were fetched to determine the operation that it w
perform.
iii. Execution i.e it controls the execution of the instructions storing the result i.e the process of storing the re
in the main memory.

NOTE: The collectionof these four functions together is referred to as MACHINE CODE or INSTRUCTION CYCLE of the C

Program Counter (PC): Instructions are fetched from the memory, decoded and then educated.

Current Instruction Register (CIR): When an instruction is fetched from the memory. it means that that instruction has be
placed somewhere and it is the job of the CIR to store these instructions.

Memory Address Register (MAR): This is a register that contains the address of the data that is being accessed on the ma
memory.

Memory Data Register: This is a register that holds the content of the last selected words read from or written to the main
memory.

Accumulator: Accumulator is that part of the memory of the computer used for storing data, information and instruction.

System Clock: This is an accurate, very fast electronic timer. It makes sure that all the chips that used to be synchronized a
synchronized inside the computer.

WEEK 5-6
MEMORY UNIT
Memory refers to data storage that comes in form of a chip. The memory units of a computer stores data temporarily for
rapid or quick retrieval. The basic unit for computer memory is bits.

TYPES OF MEMORY
1. Primary Memory: This can also be referred to as the main memory. It consists of devices that hold
instructions and data for fast and correct access by the computer's CPU. It is non-volatile[i.e cannot be easily lost].
There are 2 types of primary memory which are: Read Only Memory [ROM] and Random Access Memory [RAM].

Read Only Memory [ROM]

ROM is a non-volatile memory that retains data stored on it even after the computer is powered off. The data inside th
ROM cannot be changed. The OS [Operating System] boot records are stored inside the ROM.

TYPES OF ROM
1. PROM [Programmable Read Only Memory]: The PROM is a version of memory chip that can be programmed
the user. Once the PROM has been programmed, the information written is permanent and cannot be erasedor delete

2. EPROM [Erasable Programmable Read Only Memory]: EPROM is a version of memory chip that can be erased o
re-programmed. It requires an ultra-violet light to erase its content.

3. EEPROM [Electronic Erasable Programmable Read Only Memory]: The EEPROM can be replaced and re-
programmed using an electrical charge without the need of moving the chip from the computer system. It is used to
store information for the computer BIOS [Basic Input and Output System].

RAM [Random Access Memory]

RAM is the part of the primary memory that holds the data and program that the CPU is processing. The CPU reads and
writes onto the RAM as often as required. They are volatile because the content is lost when the computer is powered off.

2. Secondary Storage: It is also known as auxilliary storage/memory or mass storage. It is any storage device th
is used to store data and information and programmes outside the primary mmemory. They are non-volatile and have
higher storage capacity but the access time is slow compared to the primary storage. It is alao referred to as backup
storage.
Common types of Secondary storage devices:
· Floopy disk
· Hard disk
· Flash drive
· Memory card
· Optical disk

Types of Optical disk

1. Compact Disk [CD]
2. Digital Video Disk [DVD]

3. Compact Disk [CD]: The CD is a small, portable kind of disk used for backing up data. They are used for recording,
storing and playing of audio, video and any other information in digital form.
4. Digital Video Disk [DVD]: This is a digital device of the same size of the CD but of the higher capacity. It can be sim
sided or double-sided. It comes in different formats such as DVD+RW, DVD+R, DVD-Video, DVD-ROM.
RW- Rewritable
R- Recordable
UNITS OF STORAGE
Bit: It is a basic unit of information in the computer. It is expressed as 0 and 1in Binary notation e.g 0110.

Nibble: It is a storage unit that is made up of 4 bits. It is equal to 4 bits or half on an octal. An octal is equal to 8 bits.

Byte: The byte is a unit of digital information in computing. It is equivalent to 2 nibbles or 8 bits. The size of computer
memory is determined by byte.

Kilobyte: It is used to measure memory space. 8 bits is equal to 1 byte. Then 1024 bytes is equal to 1 kilobyte.
8 bits = 1 byte
1024 byte = 1 kilobyte

Megabyte: A megabyte is equal to 1 million. It is a unit of information that consists of 1,048,576 bytes i.e 1024 bytes X 10
bytes [10242] = 1,048,576 bytes. So therefore,
1024 bytes X 1024 bytes = 1MB

Gigabyte: This is a unit of information that is equal to 1 billion [1,073,741,824 bytes] = 10243 bytes. That is, 1024 X 1024 X
1024 bytes = 1,073,741,824 bytes = 1GB

Terabyte: This is a unit of information that is equal to a trillion [1,099,511,627,776 bytes]. That is, 1024 bytes X 1024 byte
1024 bytes X 1024 bytes = 10244 bytes.
1,099,511,627,776 bytes = 1TB

CONVERSION FROM ONE UNIT TO ANOTHER

4 bits = 1 nibble
1 byte = 8 bits or 2 nibbles
1 bit = 0.25 nibble
1 bit = 0.13 bytes
1 bit = 0.00098KB
1 bit = 0.00000095KB

EXAMPLE:

Convert 483 bits to byte

Solution
1 bit = 0.13 byte
483 bits X 0.13 bytes
= 62.75 bytes.
Convert 388 bits to nibble
Solution
1 bit = 0.25 nibble
388 bits X 0.25 nibble
= 97 nibbles.

Convert 1.44MB to bytes

Solution
1 MB = 1,048,576 bytes
Then 1.44MB = x
= 1,048,576 X 1.44
1.44 MB = 1,509,949.44 bytes.

Convert 2000KB to GB
Solution
If 1024 bytes = 1KB
Then x bytes = 2000KB
x bytes = 2,048,000 bytes

Convert to GB
If 1,073,741,824 bytes = 1GB
Then 2,048,000 bytes = xGB
x = 2,048,000
1,073,741,824
x = 0.001907GB.