Exam mistakes

Question 1

Why is Harvard Architecture preferred over Von Neumann

Answer 1

Instructions and data are accessed simultaneously

Instructions and data stored in parallel, so reduces ‘bottleneck’ problem

Avoids possibility of data being executed as code (which is one method that can be exploited by hackers)

Question 2

When normalising a floating point number, when should the exponent be positive?

Answer 2

When you’re moving the decimal point to the left (so the exponent increases to accomodate for it)

Question 3

When normalising a floating point number, when should the exponent be negative?

Answer 3

When you’re moving the decimal point to the right (so the exponent decreases to accomodate for it)

Question 4

What effect does increasing the mantissa have?

Answer 4

• Decreases exponent, so reduces range but increases precision

Question 5

What effect does increasing the exponent have?

Answer 5

• Decreases mantissa, so increases range but decreases precision

Question 6

How many bits in a byte?

Answer 6

8

Question 7

What are the steps required in converting from floating point to decimal?

Answer 7

Find value of exponent
Shift mantissa by bits of exponent
If mantissa is negative, convert to a positive value

Question 8

How to find absolute error?

Answer 8

(intended value) - (actual represented value)

Question 9

How to find relative error?

Answer 9

absolute error/intended value x 100

Question 10

How do you create a table in SQL

Answer 10

CREATE TABLE tablename (

)

Question 11

How do you add a column to a table?

Answer 11

ALTER TABLE tablename
ADD columnname Datatype

Question 12

How do you delete a column in a table?

Answer 12

ALTER TABLE tablename
DROP COLUMN columnname

Question 13

How do you change the datatype of a column?

Answer 13

ALTER TABLE tablename
MODIFY COLUMN columnname newdatatype

Question 14

How do you insert values into a table?

Answer 14

INSERT INTO tablename(column1, column2…)
VALUES(value1, value2, …)

Question 15

How do you update a record

Answer 15

UPDATE tablename
SET column1 = value1, column2 = value2 etc
WHERE columnX = Value

Question 16

How do you delete a record

Answer 16

DELETE FROM tablename
where columnX = value

Question 17

What are the conditions for Vernam Cipher?

Answer 17

The key must be (at least) as long as the data to be encrypted/plaintext;
The key must not be reused // key must only be used once;
The key must be (truly) random;
The key must be kept securely / not revealed / only known by user(s);

Question 18

What are the principles of operation of an optical disk?

Answer 18

• A high powered laser is used to burn “pits” into the disc. Areas which have not been pitted are called lands. Pits are represented with 0s and the transition between a pit and a land is represented with a 1.

A low powered laser is used to shine light onto the disk. It measures the intensity of the light that has been reflected back. Areas which light has not been reflected well are pits, and areas which light has been reflected well are lands.

other forms of discs such as CD RW may use a high powered laser to burn a spot, and then polarise the spot with a magnet before cooling or using a phase change alloy.

Question 19

How can a server’s performance be increased?

Talk about:
Hardware improvements
Network design
Database design and software

Answer 19

Hardware improvements
- More processor cores (more instructions can be executed simulataneously)

• Use SSD over HDD (Faster read write speed)
• Increase address bus width and data bus width, word lines

Network improvements:
- Use wired network over wireless network
- Use star topology
- Use NICs with high data transfer rate

Database design and software
- Normalise database to 3NF
- Software should use efficient searching algorithms
- Software should be compiled

Question 20

Why is technology making it difficult for legislators to prosecute cyber criminals?

Answer 20

Criminals can hide their location/use VPN, hide MAC address, and can maintain anonymity

Tech evolves quickly so more new types of crime becoming possible

Global nature of Internet means crimes may be committed in one country from outside its direct jurisdiction

Question 21

How does increasing data bus width improve processor performance?

Answer 21

Increases the amount of data that can be transferred at one time

Question 22

In this SQL query querying two tables, what are the mistakes? :

SELECT VetForename, VetSurname
FROM Surgery, Vet
WHERE Town = Torquay

What other database question mistakes could be there

Answer 22

1. ‘Torquay’ is a string and so should be in quotations
2. There is no join clause linking the two tables that are being searched

Datatypes being referred to before the identifier, no data types for some entities, etc