Term: 2^{nd} Term
Week: 4
Class: Senior Secondary School 3
Age: 17 years
Duration: 40 minutes of 2 periods each
Date:
Subject: Computer studies and ICT
Topic: Overview of Number bases II
SPECIFIC OBJECTIVES:
At the end of the lesson, pupils should be able to
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, pictures, Data Processing for senior Secondary Education by Hiit Plc, WAPB Computer Studies for Senior Secondary III by Adekunle et al, Online Materials.
INSTRUCTIONAL PROCEDURES
PERIOD 12
PRESENTATION 
TEACHER’S ACTIVITY 
STUDENT’S ACTIVITY 
STEP 1 INTRODUCTION 
The teacher reviews the previous lesson on binary and decimal number bases 
Students pay attention 
STEP 2 EXPLANATION 
He explains the number bases and lists all the digits of the octal and hexadecimal number bases

Students pay attention and participates 
STEP 3 DEMONSTRATION 
He then performs some calculations on conversion from one base to another 
Students pay attention and participate 
STEP 4 NOTE TAKING 
The teacher writes a summarized note on the board 
The students copy the note in their books 
NOTE
NUMBER BASE SYSTEM
OCTAL NUMBER SYSTEM
The octal number system is a base 8 number system, and uses the digits from 0 to 7.
Programs often display in an octal format because it can be translate relatively in binary format, each digit in the octal number system represents a power of base 8.
For example the binary representation for decimal 74 is 1001010, which group into 1001010, so the octal representation is 112
1128 = 1 x 8^{2} + 1 x 8^{1} + 2 x 8^{0}
= (1 x 64) + (1 x 8) + (2 x 1)
= 64 + 8 + 2
= 74.
So, the decimal equivalent of octal number 1128 is 7410. Since there are only 8 digit (08) in the octal number system, 3 bits are sufficient to represent an octal number in a binary digits.
OCTAL 
BINARY 
0 
000 
1 
001 
2 
101 
3 
011 
4 
100 
5 
101 
6 
110 
7 
111 
With this table, it is easy to translate octal and binary system for example
65_{8} = 110 101_{2}
17_{8} = 001 111_{2}
HEXADECIMAL NUMBER SYSTEM
In the hexadecimal number system is a number with a base of 16, usually written using symbols 09 and AF.
For example, the decimal number 79 whose binary representation is 01001111 can be written as 4F in hexadecimal ( 4 = 0100, F = 1111 ) for example 1FF16 = 1 x 132 + F x 161 + F x 160
= 1 x 256 + 15 x 16 + 16 x 1
= 511.
Thus, the decimal equivalent of hexadecimal number 1FF16 is 51110. Since there are only 16 digits in the hexadecimal number system, 4 bits are sufficient to represent any hexadecimal number in binary.
The current decimal number system was first introduced to the computing world in 1963 by international business machine (IBM). An early version that used the digit 09 and u2 was introduced in 1956, in the Bendix G15 computer
The table given below displays the binary and decimal equivalent of some hexadecimal numbers
HEXADECIMAL 
BINARY 
DECIMAL 
0 
0000 
0 
1 
0001 
1 
2 
0010 
2 
3 
0011 
3 
4 
0100 
4 
5 
0101 
5 
6 
0110 
6 
7 
0111 
7 
8 
1000 
8 
9 
1001 
9 
A 
1010 
10 
B 
1011 
11 
C 
1100 
12 
D 
1101 
13 
E 
1110 
14 
F 
1111 
15 
The hexadecimal number 4B3A translates the following binary number.
4 B 3 A
0100 1011 0011 1010
EVALUATION: 1. Explain the following and list the digits
2a. Convert 41_{8} to a binary number. b. Convert 10_{8} to a binary number.
3a. Convert A2B_{16} to an equivalent binary number.
b. Convert E_{16}to an equivalent binary number.
c. Convert 30_{16}to an equivalent binary number.
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively