#Exam Questions 
##Instructions Edit this document and answer the questions in the sections surrounded by ```.
There are 30 marks available and are awarded grades as follows:
| Score | Grade |
|---|---|
| <6 | U |
| 6+ | G |
| 9+ | F |
| 12+ | E |
| 15+ | D |
| 18+ | C |
| 21+ | B |
| 24+ | A |
| 27+ | A* |
##Data Representation
###1 - Why do we represent data using binary when using computers (1 mark)
because it is easier for the computer to process as there are only two modes; on and off
###2 - How would we represent the number 147 in binary? (1 mark)
10010011
###3 - Can you convert the hexadecimal number b5 to denary, there is a mark for you working. (2 marks)
181 - 5=5 B=176
###4 - Here is a function written is pseudocode.
FUNCTION validUser (users , user)
FOR x <-1 to LEN(users)
IF users[x] = user
RETURN True
ENDIF
ENDFOR
RETURN False
ENDFUNCTION
(a) What type of data is users? (1 mark)
variable
(b) What type of data is returned by this function? (1 mark)
Boolean
##Errors ###6 - This program is supposed to find the mean of a list of numbers and print it out for the user:
line1: tot <- 0
line2: nums <- [1,6,4,2,5,3]
line3: FOR x <- to LEN(nums)
line4: tot <- nums[x]
line5: ENDFOR
line6: mean <- tot
line7: OUTPT mean
(a) On which line is there a syntax error? (1 mark)
7
(b) What is meant by a syntax error? (1 mark)
misuse of a programming function resulting in a program crash
(c) Identify a logical error in the program and suggest how this might be fixed. (2 marks)
answer here
(d) Describe and give an example of the 3rd kind of programming error. (2 marks)
Runtime error
An error that makes the program crash during its runtime.
dividing by zero, referencing missing files, calling invalid functions, or not handling certain input correctly.
##Algortithms ###7 - Write an algorithm that if given a list of numbers could find the largest. Try to use pseudocode.
A= Current number
B= Next number
C= Largest number
recieve numbers
A=C
If B>C then B=C #Repeat however many times nessecary
display C
##Networking ###8 - Research the following methods (topologies) for connecting devices to a network. In each case give a description and at least 1 advantage and 1 disadvantage.
Bus Topology (6 marks)
Describe: Uses a central 'bus' cable with other smaller outgoing wires to send data to each client.
Advantages: Good for Local area networking as the method is very linear
Disadvantages: There is a high limit on cable length and the number of clients that can be involved
Ring Topology (6 marks)
Describe: Sends data between each client system originating from the server in a circular layout
Advantages: Requires a less powerful server as data is being sent to only the first client system
Disadvantages: Not robust; if a client system breaks the ones after it do the same due to the ring layout
Star Topology (6 marks)
Describe: Sends data to clients from the server directly in individual pathways
Advantages: Minimal reliance on the client; if one system malfunctions it wont result in others doing so
Disadvantages: Requires a more powerful server to handle each client system being sent data