Where hexadecimal is used in computer science

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Quick Questions

Shade in the A or B circle for each question.

1. A web designer needs an orange colour code. Which one is a valid hexadecimal colour?

A #FF8800

B #GG8800

2. In the colour code #FF8800, what does the first pair FF set?

A Red at its maximum value (255)

B Blue at its minimum value (0)

3. Why do HTML and CSS colour codes use hexadecimal?

A Browsers cannot understand binary or denary numbers

B It is a short way to write the 24 bits of a colour

4. Which of these is a MAC address written in hexadecimal?

A 00:1A:2B:3C:4D:5E

B 00:1A:2B:3C:4D:5Z

5. A memory dump lists the contents of memory. Why are the addresses shown in hexadecimal?

A Memory chips can only store hex digits

B Hex is shorter and easier for people to read than long binary

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1color: #FF8800;		AComputers store data in binary. Hex is only a shorter way for people to read and write binary values.
200:1A:2B:3C:4D:5E		BError 0x80070005: Access denied
3Hexadecimal lets programmers read a memory address or memory dump value compactly instead of a long binary string		CA CSS colour written as hexadecimal: FF red, 88 green, 00 blue (one byte per colour)
4Error codes are shown in hexadecimal so a technician or programmer can quickly look them up and debug the fault		D0x7FFE 4A10
5color: #GG8800;		EA MAC address: 6 bytes shown as 12 hex digits to identify a network device
6Hex is used because computers store data in hexadecimal instead of binary		FG is not a hexadecimal digit. Hex uses only 0-9 and A-F, so #GG8800 is not a valid colour code.

Definitions

hexadecimal

Fill in the Blanks

Complete each line of code by filling in the missing parts.

color: _FF8800;

background: #__0000;

macbits = 12 * _

address = __1A3F

print(___(255))

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A h1 {

B color: #FF8800;

C background: #0000GG;

D }

Question 2

A address ← 0x1G3F

B OUTPUT address

C OUTPUT address + 1

Question 3

A hex ← FF

B nibble1 ← 1111

C nibble2 ← 1111

D binary ← 11110000

Question 4

A colour ← #FF8800

B red ← FF

C green ← FF

D blue ← 00

Question 5

A code ← 0x0B

B digit1 ← 0

C digit2 ← 11

D denary ← 16 * digit2 + digit1

Answer Key

Where hexadecimal is used in computer science

Section A: Quick Questions

A — #FF8800

A — Red at its maximum value (255)

B — It is a short way to write the 24 bits of a colour

A — 00:1A:2B:3C:4D:5E

B — Hex is shorter and easier for people to read than long binary

Section B: Match the Pairs

color: #FF8800; → A CSS colour written as hexadecimal: FF red, 88 green, 00 blue (one byte per colour)

00:1A:2B:3C:4D:5E → A MAC address: 6 bytes shown as 12 hex digits to identify a network device

Hexadecimal lets programmers read a memory address or memory dump value compactly instead of a long binary string → 0x7FFE 4A10

Error codes are shown in hexadecimal so a technician or programmer can quickly look them up and debug the fault → Error 0x80070005: Access denied

color: #GG8800; → G is not a hexadecimal digit. Hex uses only 0-9 and A-F, so #GG8800 is not a valid colour code.

Hex is used because computers store data in hexadecimal instead of binary → Computers store data in binary. Hex is only a shorter way for people to read and write binary values.

Section C: Definitions

hexadecimal — Base-16 notation that shortens binary so people can read and write it. Used in colour codes, MAC addresses, memory addresses and error codes.

Section D: Fill in the Blanks

color: #FF8800;

background: #FF0000;

macbits = 12 * 4

address = 0x1A3F

print(hex(255))

Section E: Spot the Error

C — Hexadecimal colour codes can only use the digits 0-9 and the letters A-F. G is not a hex digit, so the blue value should be #0000FF.

A — Memory addresses are written in hexadecimal, which only uses 0-9 and A-F. G is not valid, so the line should be address ← 0x1A3F.

D — Each hex digit is one 4-bit nibble. F is 1111, so FF is 11111111, not 11110000.

C — In #FF8800 the colour is split into pairs: red FF, green 88, blue 00. The green value should be 88.

D — The first hex digit is worth 16 and the second is worth 1. The calculation should be 16 * digit1 + digit2, which gives 11 for the error code 0x0B.