IGCSE CS Chapter 1 - 3 Theory

Which numbering system is used in computers?

• Binary

• Decimal

• Octal

• Hexadecimal

Answer explanation

The binary numbering system, which uses only 0s and 1s, is the fundamental language of computers. All data and instructions are ultimately represented in binary, making it the correct choice.

What is the base of the hexadecimal system?

• 2

• 8

• 10

• 16

Answer explanation

The hexadecimal system is a base-16 numeral system, which means it uses 16 distinct symbols (0-9 and A-F) to represent values. Therefore, the correct answer is 16.

Which bit is the most significant in a binary number?

• Rightmost

• Leftmost

• Middle

• None

Answer explanation

In a binary number, the leftmost bit is the most significant because it represents the highest value. Each bit to the right represents progressively lower values, making the leftmost bit crucial for determining the overall value.

What is the decimal equivalent of hexadecimal 'A'?

• 8

• 9

• 10

• 11

Answer explanation

The hexadecimal 'A' represents the decimal value 10. In hexadecimal, the digits range from 0-9 and then A-F, where A corresponds to 10. Therefore, the correct answer is 10.

How do you convert binary to decimal?

• Divide by 2

• Multiply by 2

• Use powers of 2

• Subtract 2

Answer explanation

To convert binary to decimal, use powers of 2. Each binary digit represents a power of 2, starting from the rightmost digit (2^0). Multiply each digit by its corresponding power and sum the results to get the decimal value.

What is the largest value that can be stored in 4 bits?

• 7

• 8

• 15

• 16

Answer explanation

In 4 bits, the maximum value is calculated as 2^4 - 1, which equals 15. This is because each bit can be either 0 or 1, allowing for values from 0 to 15. Therefore, the largest value that can be stored in 4 bits is 15.

Which of the following is a method of binary addition?

• Decimal Expansion

• Bitwise Addition

• Carry Method

• Hex Shift

Answer explanation

The Carry Method is a technique used in binary addition where bits are added together, and if the sum exceeds 1, a carry is generated to the next higher bit. This method is fundamental to binary arithmetic.

What is overflow in binary addition?

• Losing excess bits

• Having extra bits

• Using all bits

• Skipping bits

Answer explanation

Overflow in binary addition occurs when the result exceeds the maximum value that can be represented with the available bits, leading to losing excess bits. This is why the correct answer is 'Losing excess bits'.

Which of the following uses hexadecimal?

• IPV4 Addresses

• ASCII

• MAC Addresses

• RGB Colors

Answer explanation

MAC Addresses use hexadecimal notation to represent the 48-bit address, typically displayed as six pairs of hexadecimal digits. In contrast, IPv4 addresses use decimal, ASCII represents characters, and RGB colors use decimal or percentages.

What does ASCII stand for?

• American System for Code Interchange

• American Standard Code for Information Interchange

• Automated System for Computer Input

• Advanced System for Character Interface

Answer explanation

ASCII stands for American Standard Code for Information Interchange. It is a character encoding standard used for representing text in computers and communication equipment.