JSS2: COMPUTER STUDIES  1ST TERM

Computer Software  Week 14 Topics1 Quiz

Operating System  Week 29 Topics1 Quiz

Four Good Definitions of Computer Program

Operating System

Translators & Utility Programs

Advantages of Operating System

Functions of Operating System

Classification of Operating Systems

Examples and Uses of Operating Systems

Advantages of Windows Over Earlier Operating Systems

GUI And CommandLine (CLI) O/S

Four Good Definitions of Computer Program

Computer Memory: Primary And Secondary Memory  Week 35 Topics1 Quiz

Computer Memory II: Secondary Memory (Backing Storage)  Week 42 Topics1 Quiz

Number System I  Week 54 Topics1 Quiz

Number System II  Week 63 Topics1 Quiz

Units of Storage In Computer  Week 72 Topics1 Quiz

Problem Solving Skills With Computer  Week 85 Topics1 Quiz

Computer Programming Languages  Week 93 Topics1 Quiz
Quizzes
Octal Number
Topic Content:
 Conversion from Decimal to Octal
 Conversion of Octal to Decimal
 Worked Examples
An octal number is a number in base 8 and the place values increases in the power of 8.
Conversion from Decimal to Octal:
The conversion is similar to binary conversion but the only difference is that rather than dividing by 2 for the binary number, we would divide by 8 for an octal number until the last number is zero.
The following steps could be taken. Continue to divide the decimal number by 8 until the last division is zero and save the remainder as in the previous conversion.
Worked Example 1:
Convert 400 to octal
Solution
Answer: 400_{10} = 620_{8}
Worked Example 2:
Convert 12 decimal to octal
Solution
Answer: 12_{10} = 14_{8}
Worked Example 3:
Convert 106_{10} to octal
Solution
Answer: 106_{10} = 152_{8}
Worked Example 4:
Convert 1024 to base 8
Solution
Answer: 1024_{10} = 2000_{8}
We can also convert from other bases to decimals as shown in the examples below
Worked Example 5:
Convert 111_{10} to base 4
Solution
Answer: 111_{10} = 1233_{4}
Worked Example 6:
Convert 280_{10} to hexadecimal
Solution
Answer: 280_{10} = 118_{16}
Conversion of Octal to Decimal:
Both the expansion and place value methods could be used.
Worked Example 6:
Convert 724_{8} to decimal
Step 1:
Then write down the base raised to the place value.
Place value  8^{2}  8^{1}  8^{0} 
Binary Number  7  2  4 
Step 2:
Multiply each digit by its base raised to the corresponding place value.
724_{8} = (7 × 8^{2}) + (2 × 8^{1}) + (4 × 8^{0})
724_{8} = (7 × 64) + (2 × 8) + (4 × 1)
724_{8} = 448 + 16 + 4
= 468_{10}
Answer: 724_{8 }= 468_{10}
Worked Example 7:
Convert 210_{ 8} to decimal
Solution
Step 1:
Then write down the base raised to the place value.
Place value  8^{2}  8^{1}  8^{0} 
Binary Number  2  1  0 
Step 2:
Multiply each digit by its base raised to the corresponding place value.
210_{8} = (2 × 8^{2}) + (1 × 8^{1}) + (0 × 8^{0})
210_{8} = (2 × 64) + (1 × 8) + (0 × 1)
210_{8} = 128 + 8 + 0
= 136_{10}
Answer: 210_{8} = 136_{10}