GCSE COMPUTER SCIENCE PAPER 1: ALL
THEORY (EDEXCEL) Exam Questions and
Answers(CORRECT/UPDATE)
TOPIC 1: COMPUTATIONAL THINKING - ANSWER-TOPIC 1: COMPUTATIONAL
THINKING
Computational Thinking - ANSWER-Process used to solve complex problems. It means
formulating a problem and expressing it's solution in such a way that a computer can
carry it out
Abstraction - ANSWER-Identifying the key parts of the problem and removing any
unnecessary detail so it becomes easier to solve
Decomposition - ANSWER-Breaking down a complex problem into smaller, more
manageable parts which are easier to solve.
What are subroutines? - ANSWER-Subroutines are small blocks of code in a modular
program designed to perform a particular task
Decomposition creates subroutines. List some advantages of these. - ANSWER--Makes
debugging and maintaining the program easier
-Subroutines can be tested seperately and shown to be correct
-A particular subroutine can be called several times in the program
What are flowcharts? - ANSWER-A usefool tool that can be used to develop solutions to
a problem. They graphically represent steps in a problem
What is pseudocode useful for? - ANSWER-Useful for developing an algorithm using
programming-style constructs, but it is not an actual programming language
Why is pseudocode useful? - ANSWER-The programmer can concentrate on figuring
out how to solve the problem without worrying about the details of how to write each
statement in the programming language they will use
Define algorithm - ANSWER-A sequence of steps that can be followed in order to
complete a task
Explain the difference between an algorithm and a computer program. - ANSWER-A
computer program is one way of implementing an algorithm in a particular language
(like python) but the algorithm is the series of instruction and it's order
,What is a trace table used for? - ANSWER-Show how the values of variables change
during the execution of the program. As each line of code is executed, the current value
of any variable that is changed is written in the appropriate column on the table
What is a syntax error and what does it do? - ANSWER-A syntax error will prevent your
program from running. It is typically caused by a mistake in the spelling or 'grammar' of
the code.
What is a logic error and what does it do? - ANSWER-A logic error may crash your
program or produce an unexpected/incorrect output. Logic errors occur due to things
such as < or > symbols, or brackets, which could affect loop conditions or range checks.
What is a runtime error and what does it do? - ANSWER-A runtime error is one which
will be detected when the program is run. It may be caused by a logic error, erroneous
user input or by the program not allowing for a condition such as a user inputting 0 or
entering no data at all. Division by 0 may also cause it.
Name 2 search algorithms - ANSWER-Binary and Linear search
What does a binary search do? - ANSWER-Can be used to search a list in numerical or
alphabetical order. It works by repeatedly dividing in half the portion of the list that could
contain the required data item
What does a linear search do? - ANSWER-In a linear search, the item will be checked
one by one in the list. This is very slow for large lists but necessary if the list is not
sorted.
Linear Search VS Binary Search - ANSWER-Linear:
- Inefficient but easy to implement
Binary:
-Very efficient and fast, but harder to implement and only works on sorted lists
How does a bubble sort work? - ANSWER-It works by repeatedly going through the list
to be sorted and swapping adjacent elements if they are in the wrong order
How does a merge sort work? - ANSWER-In the first stage, the list is succesively
divided in half until each sublist is the length of one. In the second stage each pair of
sublists is repeatedly merged to produce new sublists until one, final sorted list is
produced.
Bubble sort VS Merge sort - ANSWER-Merge sort: More complex, recursive algorithm
(it uses a subroutine that calls itself). Many times faster for large data sets.
Bubble sort: Iterative algorithm, meaning it uses WHILE and/or FOR loops, repeating
the same step many times
, How is efficiency of an algorithm calculated? - ANSWER-The efficiency of an algorithm
can be measured by the time it takes to execute , or the amount of memory required for
a given dataset.
QUESTION: What are the benefits of using decomposition and abstraction? -
ANSWER-Decomposition breaks down a complex problem into subproblems, which are
much easier to solve, easier to understand and can also be examined in more detail.
Therefore, if a problem is not decomposed it is much harder to solve.
Abstraction filters out unecessary information. Abstraction allows programmers to create
a general idea of what the problem is and how to solve it. The process instructs them to
remove all specific detail and any patterns that will not help find a solution. An idea of
the problem can then be formed. This idea is known as a 'model'
TOPIC 2: DATA - ANSWER-TOPIC 2: DATA
A computer is made up of... - ANSWER-Billons of switches, each with an off or on state.
What is binary? - ANSWER-This is how the on/off is represented. off is 0 and on is 1.
Why is binary important? - ANSWER-It is the only language computers can understand,
so everything must be converted into binary before being fed into a computer.
There are two types of binary shift. Logical and arithmetic. What does a logical shift do?
- ANSWER-A logical shift moves all the bits in a given binary number either to the left or
to the right by a given number of places. All the empty spaces are then filled with
zeroes.
What does an arithmetic shift do? - ANSWER-Left arithmetic shift is the same as a left
logical shift.
With a right arithmetic shift of one place, each bit moves right. The rightmost bit is
discarded and the leftmost bit is filled with the previous value.
Why are hexadecimals used? - ANSWER-- Easier to read
- Easier to remember
- Take up less data
When are they used? - ANSWER-- Colour values
- MAC addresses
- memory address locations
What is meant by character encoding? - ANSWER-Each character on a keyboard has a
binary code which is transmitted to the computer each time a key is pressed
What is a pixel? - ANSWER-Short for a picture element, the smallest identifiable area of
an image
THEORY (EDEXCEL) Exam Questions and
Answers(CORRECT/UPDATE)
TOPIC 1: COMPUTATIONAL THINKING - ANSWER-TOPIC 1: COMPUTATIONAL
THINKING
Computational Thinking - ANSWER-Process used to solve complex problems. It means
formulating a problem and expressing it's solution in such a way that a computer can
carry it out
Abstraction - ANSWER-Identifying the key parts of the problem and removing any
unnecessary detail so it becomes easier to solve
Decomposition - ANSWER-Breaking down a complex problem into smaller, more
manageable parts which are easier to solve.
What are subroutines? - ANSWER-Subroutines are small blocks of code in a modular
program designed to perform a particular task
Decomposition creates subroutines. List some advantages of these. - ANSWER--Makes
debugging and maintaining the program easier
-Subroutines can be tested seperately and shown to be correct
-A particular subroutine can be called several times in the program
What are flowcharts? - ANSWER-A usefool tool that can be used to develop solutions to
a problem. They graphically represent steps in a problem
What is pseudocode useful for? - ANSWER-Useful for developing an algorithm using
programming-style constructs, but it is not an actual programming language
Why is pseudocode useful? - ANSWER-The programmer can concentrate on figuring
out how to solve the problem without worrying about the details of how to write each
statement in the programming language they will use
Define algorithm - ANSWER-A sequence of steps that can be followed in order to
complete a task
Explain the difference between an algorithm and a computer program. - ANSWER-A
computer program is one way of implementing an algorithm in a particular language
(like python) but the algorithm is the series of instruction and it's order
,What is a trace table used for? - ANSWER-Show how the values of variables change
during the execution of the program. As each line of code is executed, the current value
of any variable that is changed is written in the appropriate column on the table
What is a syntax error and what does it do? - ANSWER-A syntax error will prevent your
program from running. It is typically caused by a mistake in the spelling or 'grammar' of
the code.
What is a logic error and what does it do? - ANSWER-A logic error may crash your
program or produce an unexpected/incorrect output. Logic errors occur due to things
such as < or > symbols, or brackets, which could affect loop conditions or range checks.
What is a runtime error and what does it do? - ANSWER-A runtime error is one which
will be detected when the program is run. It may be caused by a logic error, erroneous
user input or by the program not allowing for a condition such as a user inputting 0 or
entering no data at all. Division by 0 may also cause it.
Name 2 search algorithms - ANSWER-Binary and Linear search
What does a binary search do? - ANSWER-Can be used to search a list in numerical or
alphabetical order. It works by repeatedly dividing in half the portion of the list that could
contain the required data item
What does a linear search do? - ANSWER-In a linear search, the item will be checked
one by one in the list. This is very slow for large lists but necessary if the list is not
sorted.
Linear Search VS Binary Search - ANSWER-Linear:
- Inefficient but easy to implement
Binary:
-Very efficient and fast, but harder to implement and only works on sorted lists
How does a bubble sort work? - ANSWER-It works by repeatedly going through the list
to be sorted and swapping adjacent elements if they are in the wrong order
How does a merge sort work? - ANSWER-In the first stage, the list is succesively
divided in half until each sublist is the length of one. In the second stage each pair of
sublists is repeatedly merged to produce new sublists until one, final sorted list is
produced.
Bubble sort VS Merge sort - ANSWER-Merge sort: More complex, recursive algorithm
(it uses a subroutine that calls itself). Many times faster for large data sets.
Bubble sort: Iterative algorithm, meaning it uses WHILE and/or FOR loops, repeating
the same step many times
, How is efficiency of an algorithm calculated? - ANSWER-The efficiency of an algorithm
can be measured by the time it takes to execute , or the amount of memory required for
a given dataset.
QUESTION: What are the benefits of using decomposition and abstraction? -
ANSWER-Decomposition breaks down a complex problem into subproblems, which are
much easier to solve, easier to understand and can also be examined in more detail.
Therefore, if a problem is not decomposed it is much harder to solve.
Abstraction filters out unecessary information. Abstraction allows programmers to create
a general idea of what the problem is and how to solve it. The process instructs them to
remove all specific detail and any patterns that will not help find a solution. An idea of
the problem can then be formed. This idea is known as a 'model'
TOPIC 2: DATA - ANSWER-TOPIC 2: DATA
A computer is made up of... - ANSWER-Billons of switches, each with an off or on state.
What is binary? - ANSWER-This is how the on/off is represented. off is 0 and on is 1.
Why is binary important? - ANSWER-It is the only language computers can understand,
so everything must be converted into binary before being fed into a computer.
There are two types of binary shift. Logical and arithmetic. What does a logical shift do?
- ANSWER-A logical shift moves all the bits in a given binary number either to the left or
to the right by a given number of places. All the empty spaces are then filled with
zeroes.
What does an arithmetic shift do? - ANSWER-Left arithmetic shift is the same as a left
logical shift.
With a right arithmetic shift of one place, each bit moves right. The rightmost bit is
discarded and the leftmost bit is filled with the previous value.
Why are hexadecimals used? - ANSWER-- Easier to read
- Easier to remember
- Take up less data
When are they used? - ANSWER-- Colour values
- MAC addresses
- memory address locations
What is meant by character encoding? - ANSWER-Each character on a keyboard has a
binary code which is transmitted to the computer each time a key is pressed
What is a pixel? - ANSWER-Short for a picture element, the smallest identifiable area of
an image
