Hexadecimal for register and memory values in ARM Architecture - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to represent the hexadecimal value for register R1.

ARM Architecture

MOV R1, #[1]

Drag options to blanks, or click blank then click option'

A26

B0x1A

C0b11010

D1A

Attempts:

3 left

💡 Hint

Common Mistakes

Using decimal numbers without 0x prefix.

Writing hex without 0x prefix.

The prefix 0x indicates a hexadecimal number in ARM assembly. So 0x1A is the correct way to write the hex value for 26.

2fill in blank

medium

Complete the code to load the hexadecimal memory address into register R2.

ARM Architecture

LDR R2, =[1]

Drag options to blanks, or click blank then click option'

A65280

BFF00

C0xFF00

D0b1111111100000000

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting 0x prefix.

Using decimal or binary instead of hex.

The LDR instruction loads a value into a register. The address must be in hexadecimal with 0x prefix, so 0xFF00 is correct.

3fill in blank

hard

Fix the error in the code to correctly store the hexadecimal value 0x3F into register R3.

ARM Architecture

MOV R3, #[1]

Drag options to blanks, or click blank then click option'

A0x3F

B63

C0b111111

D3F

Attempts:

3 left

💡 Hint

Common Mistakes

Using decimal number without prefix.

Writing hex without 0x prefix.

In ARM assembly, immediate hexadecimal values must have the 0x prefix. So 0x3F is the correct format.

4fill in blank

hard

Fill both blanks to create a hexadecimal mask and apply it to register R4.

ARM Architecture

AND R4, R4, #[1][2]

Drag options to blanks, or click blank then click option'

A0xFF

B0x0F

C0xF0

D00

Attempts:

3 left

💡 Hint

Common Mistakes

Using masks that do not combine to the correct value.

Confusing 0x0F and 0xF0.

The mask 0xFF00 is created by combining 0xFF and 00. This mask keeps the higher byte and clears the lower byte.

5fill in blank

hard

Fill all three blanks to create a dictionary mapping registers to their hexadecimal values.

ARM Architecture

registers = { "[1]": [2], "[3]": 0x1A }

Drag options to blanks, or click blank then click option'

AR5

B0x10

CR6

D0x1F

Attempts:

3 left

💡 Hint

Common Mistakes

Using decimal numbers without 0x.

Swapping keys and values.

This dictionary maps R5 to 0x10 and R6 to 0x1A. The keys are register names and values are hex numbers.

Practice

1. What does the prefix 0x in a value like 0x1A3F indicate in ARM architecture?

easy

A. The value is a binary number

B. The value is in decimal format

C. The value is a memory address

D. The value is in hexadecimal format

Solution

1. Step 1: Understand the prefix meaning

   The prefix 0x is a standard notation used in computing to indicate that the following number is in hexadecimal (base 16) format.

2. Step 2: Differentiate from other formats

   Decimal numbers do not have this prefix, binary numbers use 0b, and memory addresses may or may not use this prefix but the prefix itself means hexadecimal.

3. Final Answer:

   The value is in hexadecimal format -> Option D

4. Quick Check:

   Prefix 0x means hexadecimal [OK]

Hint: Remember 0x means hex, not decimal or binary [OK]

Common Mistakes:

• Confusing 0x with decimal numbers
• Thinking 0x means binary
• Assuming 0x always means memory address

2. Which of the following is the correct way to write the hexadecimal value for decimal 255 in ARM assembly?

easy

A. 0xFF

B. FFx0

C. 255x0

D. 0b11111111

Solution

1. Step 1: Convert decimal 255 to hexadecimal

   Decimal 255 equals hexadecimal FF because 15*16 + 15 = 255.

2. Step 2: Write the correct hexadecimal notation

   Hexadecimal values start with 0x followed by digits and letters A-F, so 0xFF is correct.

3. Final Answer:

   0xFF -> Option A

4. Quick Check:

   Decimal 255 = 0xFF [OK]

Hint: Hex starts with 0x, then hex digits (0-9, A-F) [OK]

Common Mistakes:

• Writing the prefix after the digits
• Using decimal digits without 0x
• Confusing binary prefix 0b with hex

3. Given the ARM register value R0 = 0x1C, what is the decimal equivalent of this value?

medium

A. 12

B. 28

C. 44

D. 31

Solution

1. Step 1: Understand hexadecimal digits

   The value 0x1C has two hex digits: 1 and C. Hex digit C equals decimal 12.

2. Step 2: Calculate decimal value

   Calculate as (1 * 16) + 12 = 16 + 12 = 28.

3. Final Answer:

   28 -> Option B

4. Quick Check:

   0x1C = 28 decimal [OK]

Hint: Multiply first digit by 16, add second digit decimal [OK]

Common Mistakes:

• Treating hex digits as decimal directly
• Ignoring that C = 12 in decimal
• Adding digits without multiplying first by 16

4. An ARM instruction tries to load the value 0xG5 into a register. What is the problem with this hexadecimal value?

medium

A. The value is too large for a register

B. The prefix 0x is missing

C. Hexadecimal digits must be 0-9 or A-F; 'G' is invalid

D. Hexadecimal values cannot be loaded into registers

Solution

1. Step 1: Check valid hexadecimal digits

   Hexadecimal digits include 0-9 and letters A-F only. The letter 'G' is not a valid hex digit.

2. Step 2: Identify the error in the value

   Since 'G' is invalid, the value 0xG5 is not a valid hexadecimal number and will cause an error.

3. Final Answer:

   Hexadecimal digits must be 0-9 or A-F; 'G' is invalid -> Option C

4. Quick Check:

   Hex digits only 0-9, A-F [OK]

Hint: Hex digits only 0-9 and A-F, no other letters [OK]

Common Mistakes:

• Assuming any letter can be hex
• Thinking 0x prefix is missing
• Believing hex values can't be loaded into registers

5. You have a memory address 0x100 storing the value 0x2A. You want to add decimal 10 to this value and store it back. What is the new hexadecimal value stored at 0x100?

hard

A. 0x34

B. 0x3A

C. 0x20

D. 0x2F

Solution

1. Step 1: Convert the original hex value to decimal

   Value at 0x100 is 0x2A. Hex 2A = (2 * 16) + 10 = 32 + 10 = 42 decimal.

2. Step 2: Add decimal 10 to the value

   42 + 10 = 52 decimal.

3. Step 3: Convert the result back to hexadecimal

   52 decimal = 3 * 16 + 4 = 0x34 in hexadecimal.

4. Final Answer:

   0x34 -> Option A

5. Quick Check:

   42 + 10 = 52 decimal = 0x34 hex [OK]

Hint: Convert hex to decimal, add, then convert back to hex [OK]

Common Mistakes:

• Adding hex digits directly without conversion
• Confusing decimal and hex values
• Forgetting to convert result back to hex