Paper 1

Question 1

Selection?

Answer 1

IF….ELSE

Question 2

Iteration?

Answer 2

FOR….ENDFOR
WHILE….ENDWHILE
REPEAT…UNTIL

Question 3

4 different sorts?

Answer 3

Linear search
Bubble sort
Merge sort

Question 4

What is FOR…ENDFOR loop an example of?

Answer 4

definite iteration

Question 5

What is WHILE…ENDWHILE loop an example of?

Answer 5

indefinite iteration

Question 6

What is REPEAT…UNTIL loop an example of?

Answer 6

indefinite iteration

Question 7

What is a subroutine?

Answer 7

A named, self-contained section of code that performs a specific task.

Question 8

What are the 2 different types of subroutines?

Answer 8

1. procedures (nothing is returned)
2. functions (always returns a value using RETURN)

Question 9

What are advantages of subroutines?

Answer 9

1. easier to de-bug
2. more robust
3. Decomposing large problems into sub-tasks, making the problem easier to solve
4. Each subroutine can be tester separately
5. Can be used several times within a program
6. Maintenance is easier

Question 10

Define global variable?

Answer 10

A global variable is one which is declared in the main program and is recognised in al subroutines called from the main program.

Question 11

Define local variable.

Answer 11

Declared within the subroutine and only existing whole the function is being executed. Not recognised anywhere else in the program.

Question 12

Advantages of using local variables

Answer 12

• keeps the subroutine self-contained. Can be used in any program and there will be no confusion over which variable names in the main program might conflict with names used in a subroutine.
• Easier to debug and maintain
• If memory space is an issue, the use of local variables will save on memory as the space used by local variables is freed up when the subroutine completes
• form of abstraction

Question 13

How to make a code more understandable?

Answer 13

• Use comments to say the purpose of the program/ explain how any difficult bit of code works
• Split the program into subroutines which each perform a single well-defined task
• Use meaningful variables
• Use indentation so that it is clear where iteration and selection statements end
• Use constant variables for values such as VAT rate

Question 14

What is a syntax error?

Answer 14

• spelling mistake (prnt instead of print)
• missing key words out of constructs such as starting REPEAT loop but not writing UNTIL anywhere
• opening brackets but not closing them

Question 15

What are logic errors?

Answer 15

• missing brackets for mathematical equations
• Loops that do not execute the correct number of times because a condition is written wrong e.g x > 10 instead of x >= 10
• variables have not been initialised or are initialised in the wrong place
• flawed algorithms that don’t do what they were intended too

Question 16

Define low-level language

Answer 16

Machine code and assembly language

Question 17

What is high-level language?

Answer 17

Coding platforms like python, java etc

Question 18

What are advantage of high-level language?

Answer 18

• relatively easy to learn and are much faster to program in
• because it looks like english it is easy to read, understand, debug and maintain
• designed to make programming quick and easy for particular applications

Question 19

Advantages of low-level languages

Answer 19

Often used in embedded systems

• gives the programmer complete control over the system components so it can be used to control and manipulate specific hardware components
• Very efficient code can be written for a particular type of processor, so it will occupy less memory and execute faster than a compiled high-level language

Question 20

Differences between machine code and assembly code

Answer 20

Machine code is the code executed by the processor, and consists only of 0s and 1s. In assembly language, have to be translated into machine code before they can be executed.

Question 21

What is an assembler?

Answer 21

An assembler converts assembly language into machine code. High level language -> Assembly code (assembler) -> Machine code

Question 22

How to make a program more robust?

Answer 22

Add validation

Question 23

Advantage to stuctured approach?

Answer 23

• easier to read as program is split into smaller parts/subroutines
• easier to debug as program is split into smaller parts/subroutines

Question 24

Limitation to array

Answer 24

Only stores one data type

Question 25

Why are nested loops needed for 2D arrays?

Answer 25

To access each row, then for each row the inner row can access each item

Question 26

How do 2D arrays make use of multiple indexes?

Answer 26

One index is used for each row and a second for each item

Question 27

Difference between static and dynamic arrays?

Answer 27

Dynamic array - can change size as values can be added/removed

Static array - set size

Question 28

What is the difference between writing to an array and appending to an array?

Answer 28

Writing changes an item whereas append adds value to end of array

Question 29

3 methods of accessing files in python?

Answer 29

1. READ
2. WRITE
3. APPEND