2.1 Algorithms

Question 1

Computational thinking

Answer 1

The thought processes involved in formulating a problem and expressing its solution is such a way that a computer - human or machine - can effectively carry out.

Question 2

Abstraction

Answer 2

The process of separating ideas from specific instances of those ideas at work. Computational structures are defined by their meanings, while hiding away the details of how they work. Abstraction tries to factor out details from a common pattern so that programmers can work close to the level of human thoughts, leaving details which matter in practise, but are immaterial to the problem being solved.

Question 3

Decomposition

Answer 3

The process by which a complex problem or system is broken down into parts that are easier to conceive, understand, program and maintain.

Question 4

Algorithmic thinking

Answer 4

A way of getting to a solution by identifying the steps needed.

Question 5

Problem inputs

Answer 5

Any information or data which goes into a system.

Question 6

Problem processes

Answer 6

Anything which happens to data during a system running e.g. Performing calculations.

Question 7

Problem outputs

Answer 7

Any information or data which leaves a system.

Question 8

Structure diagram

Answer 8

A diagram that looks like an upside down tree, with one node at the top (root) and many below. It is used when designing solutions to problems in order to help break a large problem down into a number of small parts.

Question 9

Pseudocode

Answer 9

A language independent description of the steps of an algorithm. Intended for human to express and design algorithms before coding.

Question 10

Flowchart

Answer 10

A method of designing algorithms before coding using symbols.

Question 11

Trace table

Answer 11

A technique used to test algorithms, in order to make sure that no logical errors occur while the algorithms being processed. The table usually has one column for each variable. Each row of the table shows how the various values held variables change as the algorithm is running.

Question 12

Searching algorithms

Answer 12

An algorithm which attempts to find a given value in a data set.

Question 13

Binary search

Answer 13

A particularly efficient search method. It only works if records in the file are in sequence. A binary search involves accessing the middle record of the file and determining if the target record has been found or, if not, if it is before or after it in the sequence. This process is repeated on the part of the file where the target record is expected until it is found.

Question 14

Linear search

Answer 14

Involves examining each entry in turn in the file until the time is found or the end of the file is reached. Unless the files are in some useful order, a serial search has to be used.

Question 15

What is an example of abstraction in real life?

Answer 15

A map

Question 16

What is an example of decomposition in real life?

Answer 16

Crossing a road

Question 17

What is an example of algorithmic thinking in real life?

Answer 17

Solving a word search.

Question 18

Syntax error

Answer 18

A mistake in the grammar or the code. It stops the program from running.

Question 19

Logic error

Answer 19

An error that gives an unexpected output. This does not stop the program from running.

Question 20

Runtime error

Answer 20

An error that occurs whilst the program is running. Runs the program until the error occurs.

Question 21

Examples of syntax errors.

Answer 21

No colon or incorrect indentations

Question 22

Examples of logic errors.

Answer 22

< instead of >, AND instead of OR.

Question 23

Example of runtime error.

Answer 23

An invalid input by the user

Question 24

Identify and fix this error:
print(hello)

Answer 24

It is a syntax error, it should be
print(“hello”)

Question 25

Identify and fix this error:
if age < 18:
print(“You are old enough to vote”)

Answer 25

The error is a logic error, it should be:
if age > 18:
print(“You are old enough to vote”)

Question 26

Identify and fix this error:
if age > 18
print(You are old enough to vote)

Answer 26

There are multiple syntax errors, it should be:
if age > 18:
print(“You are old enough to vote”)