2.1

Question 1

name the principles of computational thinking.

Answer 1

• abstraction
• decomposition
• algorithmic thinking

Question 2

what is abstraction?

Answer 2

• the process of removing unnecessary details and including only the relevant details.

Question 3

what is 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

what is algorithmic thinking?

Answer 4

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

Question 5

state an example of abstraction.

Answer 5

• maps

Question 6

state an example of decomposition.

Answer 6

the steps taken in crossing a road

Question 7

state an example of algorithmic thinking.

Answer 7

• a recipe

Question 8

define problem inputs.

Answer 8

Any information or data which goes into a system

Question 9

define problem processes.

Answer 9

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

Question 10

define problem outputs.

Answer 10

Any information of data which leaves a system

Question 11

why do we use trace tables?

Answer 11

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

Question 12

write a step by step guide on how to create a trace table.

Answer 12

• take each line at a time and write out in a trace table the constant state of each variable.
• note down any output the program produces.
• each variable present in the program should have its own column in the trace table
• a new row should be added under any column if the state of a variable changes.

Question 13

what are the three different types of errors?

Answer 13

• syntax
• logic
• run time

Question 14

define syntax error.

Answer 14

Errors that break the grammatical rules of the programming language and stop it from being run.

Question 15

define logic error.

Answer 15

Errors which produce unexpected output, but on their own, they won’t stop the program from running.

Question 16

define runtime error.

Answer 16

A runtime error in a program is an error which occurs while the program is running after being successfully compiled.

Question 17

what is an example of a syntax error and how would you fix it?

Answer 17

• missing indentation
• add indentation

Question 18

what is an example of a logic error and how would you fix it?

Answer 18

• using the same variable name more than once
• using varied names to indicate different variables

Question 19

what is an example of a runtime error and how would you fix it?

Answer 19

• a list out of range
• correctly identify and fix it

Question 20

describe the flowchart symbols for the following:
- line
- process
- subprogram
- input/output
- decision
- terminal

Answer 20

• arrow pointing right
• rectangle
• rectangle with lines as borders on the edges
• parallelogram
• rhombus
• rectangle with curved corners

Question 21

how does binary search work?

Answer 21

• calculate a mid-point in the data set.
• check if that is the item to be found.
• If not…
  -If the item to be found is lower than the mid-point, repeat on the left half of the data set.
  - If the item to be found is greater than the mid-point, repeat on the right half of the data set.
• Repeat until the item is found or there are no items left to check.

Question 22

how does binary search require the data set to be?

Answer 22

• in order of a key field

Question 23

which is faster- binary search or linear search?

Answer 23

• binary search

Question 24

what are the main steps of writing the algorithm for binary search?

Answer 24

• initialise starting states for variables, flags and pointers
• enter a while loop
• set the midpoint
• check if we have found our item
• if we haven’t, then check to see if the item we are looking for is greater than out midpoint item
• if it is, then increment the left pointer
• if its not, then decrement the right pointer

Question 25

how does linear search work?

Answer 25

Starting from the beginning of a data set, each item is checked in turn to see if it is the one being searched for.

Question 26

how does linear search require the data set to be?

Answer 26

• doesn’t need it to be in order
• will work on any type of storage device

Question 27

is linear search efficient for smaller or larger data sets?

Answer 27

• can be efficient for smaller data sets
• is very inefficient for large data sets

Question 28

what is an example of using linear search in everyday life?

Answer 28

• looking for your favourite breakfast cereal on the shelves at a supermarket

Question 29

what are the main steps of writing the algorithm for linear search?

Answer 29

• initialise starting states for variables and flags
• enter a while loop until we find the item we are after or we reach the end of the data set
• check to see if the item we are currently at is the one we are after
• if it is then set our ‘found’ flag to true and output the item
• if its not increment i
• repeat the process