Paper 1

Question 1

What is an algorithm?

Answer 1

A sequence of steps that can be followed to complete a task.

Question 2

What is a computer program?

Answer 2

An implementation (application) of an algorithm.

Question 3

What is decomposition?

Answer 3

The process of breaking down a complex problem into sub-problems or more manageable chunks, so each sub-problem accomplishes an identifiable task.
* This makes the problem easier to understand.

Question 4

What is abstraction?

Answer 4

Abstraction is the process of removing unnecessary detail from a problem.
* This SIMPLIFIES the problem

Question 5

What makes an algorithm efficient?

Answer 5

• Takes less time to execute.
• Less calculations are required for the algorithm to be completed.

Question 6

How does the linear search algorithm work?

Question 7

Why is it important to use a meaningful identifier name?

Answer 7

• Describes the role of the variable
• Making the algorithm easier to understand

Question 8

What are the advantages of using the structured approach/ subroutines?

Answer 8

• Subroutines can be developed seperately
• It is easier to discover errors
• Subroutines can be updated without affecting the overall program

Question 9

What should the conditions of an algorithm be?

Answer 9

• Preicse
• Well-defined
• Finite

Question 10

What is pseudocode?

Answer 10

• Informal description
• Intended for human reading and understanding, but understands code
• No standardised (correct) syntax

Question 11

Flowcharts:

Answer 11

• Symol for start/end of an algorithm- ⬭
• Symbol for a process being carried out- ☐
• Symbol for a decision to be made- ⬦

Question 12

The linear search algorithm:

Answer 12

• Works by checking each element to see if it matches the target
• This repeats until a match has been found or the whole list of values has been checked
• WHEN PROGRAMMING THIS USE A BOOLEAN VALUE TO KEEP TRACK OF THE VALUE AND IF IT HAS BEEN FOUND/NOT FOUND.
  🚩- Not efficient for long lists

Question 13

The binary search algorithm:

Answer 13

• List must be ordered first to work- extra step. If this is not done, the program is inefficient and won’t work.
• OVERALL, BINARY SEARH IS MORE EFFICIENT THAN LINEAR SEARCH.

Question 14

Compare the bubble sort and merge sort algorithm.

Answer 14

• Bubble sort is less efficient than merge sort

Question 15

What is a variable?

Answer 15

• An address in memory
• That is given a name
• That is assigned a value
• That can change whilst the program is running.

Question 16

Define constant.

Answer 16

• An address in memory
• That is given a name
• That is asigned a value
• That cannot change while the program is running

Question 17

Advantages of using a constant:

Answer 17

1) You only have to change the value of the constant once in the source code. If we didn’t have the constant we’d have to hunt through the program to find all the places where we’d written 4 and change them to the new number.
2) It makes sure that our program is consistent as we only have to enter the value once.
3) If lots of people are working on the same program it stops mistakes happening.
4) It also makes your code more readable. For example if you are writing a program to calculate with circles it is much easier to have a constant called PI than to have to keep typing 3.1415…

Question 18

How do you identify a constant?

Answer 18

A constant has an ALL UPERCASE VARIABLE name.

Question 19

What are the three main constructs?

Answer 19

• Sequence - the idea of one step being done after another in a particular order
• Iteration - repeating sections of code in a loop (FOR, WHILE, REPEAT)
• Selection - changing the direction of a program based on a specific criteria (IF, SELECT CASE)

Question 20

Iteration- indefinite loop (condition controlled loop):

Answer 20

• Condition controlled loops are the that in which the end of the loop is unknown, it will continue indefinetely until the condition is met.

Question 21

Which condition controlled loop is adavntageous and why?

Answer 21

The REPEAT…UNTIL loop
* Th same effect is achieved with both WHILE…ENDWHILE and REPEAT…UNTIL loop
* But the REPEAT…UNTIL loop allows the program to enter the loop, gain an input, then test the condition at the end
* The WHILE…ENDWILE loop will keep running UNTIL the the conditio is met, but the REPEAT…UNNTIL loop only runs when the condition is met.
* This makes it more efficient.

Question 22

What are the two types of indefinite loop?

Answer 22

• Pre-controlled loops – the condition is checked before the loop starts, and will keep going whilst the condition is TRUE. E.g. END…ENDWILE
• Post-controlled loops – the condition is checked once the loop has finished, and will stop as soon as the condition is TRUE. E.g. REPEAT…UNTIL

Question 23

What is an exaple of a pre-controlled loop.

Answer 23

WHILE count < 5
count ← count + 1
ENDWHILE

Question 24

What is an example of a post-controlled loop.

Answer 24

REPEAT
count ← count + 1
UNTIL count < 5

Question 25

What is a definite loop (count-controlled loop)?

Answer 25

• A loop that has a definite amount of times to run
• If you do know how many times the loop will repeat, you use a definite loop.

Question 26

Example of a definite loop.

Answer 26

FOR count ← 1 TO 5
OUTPUT count
ENDFOR

This loop will run 5 times. Each time through the loop, count will increase by 1 until it reaches 5.

Question 27

What is nesting?

Answer 27

When a statement is put inside of another.

Question 28

Give an example of nested selection.

Answer 28

WHILE abc
FOR xyz
ENDFOR
ENDWHILE

Question 29

What is the rule for integer and string concatenation?

Answer 29

Python doesn’t allow adding/ concatenating an integer (i) and a string directly. In Python, you need to convert the integer to a string before concatenating it with another string.

for i in range (1,10):
print (str(i + “times table”))
for j in range (1,12):

Question 30

Give an examle of nested selection.

Answer 30

IF abc
IF aabc
ENDIF
ENDIF

Question 31

Define selection.

Answer 31

The ability too change the flow of the program, based on a condition thats is met.

Examples:
* If, else

Question 32

What are the 2 types of division?

Answer 32

• Integer division- // in python, DIV in pseudocode. This cuts off any number after integer, so all decimal values will be ignored.
• Real/float division- /

Question 33

Boolean operators:

Answer 33

• NOT- This reverses the input (NOT TRUE = FALSE)
• AND- This checks if both inputs are TRUE and returns TRUE __if so, __FALSE otherwise
• OR- This checks if either input is TRUE and returns TRUE if so, __FALSE __otherwise

Question 34

Pseudocode vs flowcharts:

Answer 34

• In general, pseudocode is much easier to create accurate and detailed algorithms. In flowcharts it is too easy to miss out a step, or combine the hard bits together into one block.
• However, flowcharts are a much easier way to see the flow of a program and how it runs from start to finish.
• You are able to use both in your exam, although it is recommended that you use pseudocode, as you are less likely to drop silly marks

Question 35

What is a relational operator?

Answer 35

Used to compare the relationship between two variables/values
* E.g. > or !=

Question 36

What is an arithemtic operator?

Answer 36

Used to perform a mathematical function between 2 variables/values.
* E.g. +, -, *, /, //

Question 37

Define array.

Answer 37

An array is defined as multiple spaces in memory, under a single indetifier, in order to group elements together.

Question 38

Give an example of a one dimensional array.

Answer 38

primes ← [ 2, 3, 5, 7, 11, 13 ]