1  Theory of Computer Science / Binary Uses


Exam Questions  Binary Uses
Example Question 1
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13
(a) (i) Question 13 (a) (i) starts by giving you a short explanation of how ASCII works. They give the example that the ASCII code for A is (Denary) 65 and that the ASCII code for B is (Denary)66.
Next you are told that there are two memory locations storing ASCII characters:
Location 1 = A
Location 2 = C
Now, we have been told in the question that A = 65. You should have enough knowledge of ASCII to figure out that C is going to be 67 (1 more than be at 66).
You are now required to convert the numbers 65 and 67 into binary for part (i) of the question.
Answers
Location 1 = 01000001
Location 2 = 01000011
(ii) Question (ii) requires you to convert the same two numbers into Hexadecimal. Now that we have the binary numbers for 65 and 67 the conversion process should be fairly straight forward:
Location 1 = 0100(4) 0001(1)
Location 2 = 0100(4) 0011(3)
Answers
Location 1 = 41
Location 2 = 43
(b) Question (b) is not strictly an ASCII question but it has been included into a question that initially was. This question requires you to convert the provided 12 bit binary number into Hexadecimal.
To achieve this you just need to remember to split it into nibbles and convert each one:
1111101010010111
1111 = (15)(F)
1010 = (10 (A)
1001 = 9
0111 = 7
Answer = FA97
(c) Question (c) is again not an ASCII one but has been included into a question that initially was. This question is just asking you to provide two reasons why a programmer would use hexadecimal rather than binary when debugging his program.
Answers
(a) (i) Question 13 (a) (i) starts by giving you a short explanation of how ASCII works. They give the example that the ASCII code for A is (Denary) 65 and that the ASCII code for B is (Denary)66.
Next you are told that there are two memory locations storing ASCII characters:
Location 1 = A
Location 2 = C
Now, we have been told in the question that A = 65. You should have enough knowledge of ASCII to figure out that C is going to be 67 (1 more than be at 66).
You are now required to convert the numbers 65 and 67 into binary for part (i) of the question.
Answers
Location 1 = 01000001
Location 2 = 01000011
(ii) Question (ii) requires you to convert the same two numbers into Hexadecimal. Now that we have the binary numbers for 65 and 67 the conversion process should be fairly straight forward:
Location 1 = 0100(4) 0001(1)
Location 2 = 0100(4) 0011(3)
Answers
Location 1 = 41
Location 2 = 43
(b) Question (b) is not strictly an ASCII question but it has been included into a question that initially was. This question requires you to convert the provided 12 bit binary number into Hexadecimal.
To achieve this you just need to remember to split it into nibbles and convert each one:
1111101010010111
1111 = (15)(F)
1010 = (10 (A)
1001 = 9
0111 = 7
Answer = FA97
(c) Question (c) is again not an ASCII one but has been included into a question that initially was. This question is just asking you to provide two reasons why a programmer would use hexadecimal rather than binary when debugging his program.
Answers
 It is easier to identify values
 It is easier to spot errors
Example Question 2
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4
(a) Question 4 (a) Might look daunting at first but as long as you take the time to carefully read the question you will realize that it is essentially a simple binary > denary conversion question disguised as a complicated register question.
After taking your time to read the question you should understand that each digit on the clock display is represented by a 4 bit binary number in a register. You should also understand that the top register is the first digit and it works down from there.
To answer this correctly you just need to convert each of the binary values in the 4 registers into denary, you should then place your resulting denary numbers into the clock display box.
0001 = 1
0110 = 4 + 2 = 6
0100 = 4
1001 = 8 + 1 = 9
Answer = 16:49
1 mark would be awarded for having 16 correct and the second mark is awarded for having the 49 part correct.
(b) Question 4 (b) is the same as part (a) but in reverse. This time you are given the time 17:29 and you need to convert each denary value into binary:
Answer =
1 = 0001
7 = 0111
2 = 0010
9 = 1001
1 mark is awarded for each correct digit.
(a) Question 4 (a) Might look daunting at first but as long as you take the time to carefully read the question you will realize that it is essentially a simple binary > denary conversion question disguised as a complicated register question.
After taking your time to read the question you should understand that each digit on the clock display is represented by a 4 bit binary number in a register. You should also understand that the top register is the first digit and it works down from there.
To answer this correctly you just need to convert each of the binary values in the 4 registers into denary, you should then place your resulting denary numbers into the clock display box.
0001 = 1
0110 = 4 + 2 = 6
0100 = 4
1001 = 8 + 1 = 9
Answer = 16:49
1 mark would be awarded for having 16 correct and the second mark is awarded for having the 49 part correct.
(b) Question 4 (b) is the same as part (a) but in reverse. This time you are given the time 17:29 and you need to convert each denary value into binary:
Answer =
1 = 0001
7 = 0111
2 = 0010
9 = 1001
1 mark is awarded for each correct digit.
Example Question 3
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3
(a) Question 3 (a) is not register related but rather a Hexadecimal > Binary conversion question that has been included.
To answer this you just need to remember to convert each digit individually into its own Nibble:
4 = 0100
A = 1001
F = 1111
Answer = 010010011111
(b) (i) This question really highlights the importance of reading every question carefully. The key point to this question that can be very easily overlooked is that the timer COUNTS DOWN!
Now with that in mind, the question asks you to show the binary values 30 seconds after the time shown in the registers above. The registers above show the time:
105 Hours
32 Minutes
20 Seconds
If you count down 30 seconds the resulting numbers would be:
105 hours (Unchanged)
31 Minutes
50 Seconds
Next you can simply convert each number into binary and place them into the correct register box's:
Answers
Hours  01101001
Minutes  00011111
Seconds  00110010
(ii) Part (ii) of this question asks you to convert the binary in the minutes register into Hexadecimal. You can of course only get this question correct if you got part (i) correct.
00011111
0001 = 1
1111 = F
Answer = 1F
(a) Question 3 (a) is not register related but rather a Hexadecimal > Binary conversion question that has been included.
To answer this you just need to remember to convert each digit individually into its own Nibble:
4 = 0100
A = 1001
F = 1111
Answer = 010010011111
(b) (i) This question really highlights the importance of reading every question carefully. The key point to this question that can be very easily overlooked is that the timer COUNTS DOWN!
Now with that in mind, the question asks you to show the binary values 30 seconds after the time shown in the registers above. The registers above show the time:
105 Hours
32 Minutes
20 Seconds
If you count down 30 seconds the resulting numbers would be:
105 hours (Unchanged)
31 Minutes
50 Seconds
Next you can simply convert each number into binary and place them into the correct register box's:
Answers
Hours  01101001
Minutes  00011111
Seconds  00110010
(ii) Part (ii) of this question asks you to convert the binary in the minutes register into Hexadecimal. You can of course only get this question correct if you got part (i) correct.
00011111
0001 = 1
1111 = F
Answer = 1F
Example Question 4
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1
Question 1 is a register question that also requires you to have some understanding of hexadecimal to binary conversion.
Essentially you are given 5 hexadecimal values. You need to convert each one into binary. Find the matching binary instruction (Given in the question) and then write down the corresponding operation
Answers
9 = Left (1001)
1 = Down (0001)
C = Open (1100)
3 = Close (0011)
F = Up (1111)
Question 1 is a register question that also requires you to have some understanding of hexadecimal to binary conversion.
Essentially you are given 5 hexadecimal values. You need to convert each one into binary. Find the matching binary instruction (Given in the question) and then write down the corresponding operation
Answers
9 = Left (1001)
1 = Down (0001)
C = Open (1100)
3 = Close (0011)
F = Up (1111)