Topic 2 - Programming

Question 1

What’s Declaration

Answer 1

Before variables can be used, they must be declared.
Declaring a variable means telling the computer:
What the identifier (name) should be.
What type of data will be stored.

Question 2

What’s assignment

Answer 2

Changing the value stored inside a variable is called assignment.
The value assigned to a variable must match the data type of the variable.

Question 3

Why do some languages not need to declare the variable

Answer 3

Some languages don’t need you to declare variables before you use them:
These languages automatically declare the variable before the first assignment.

Question 4

What’s input

Answer 4

Input is collecting data, usually by the keyboard.
This is written in pseudocode as:
OUTPUT “Please enter [something]…”
variable = USERINPUT

Question 5

What’s output

Answer 5

Output is putting data to the screen, usually as text.
This is written in pseudocode as:
OUTPUT “Text goes here”

Question 6

What’s a string

Answer 6

Text data.
Example:
“Hello, world!”.

Question 7

What’s a character

Answer 7

Character
A single letter of text data.
Example:
‘a’.

Question 8

What’s a Boolean

Answer 8

A True or False value.
Examples:
True.
False.

Question 9

What’s a real

Answer 9

Fractional numbers.
Examples:
0.42, 1.00.

Question 10

What’s an integer

Answer 10

Whole numbers.
Examples:
12, 0, -142.

Question 11

What are the reasons for casting

Answer 11

One of the most common reasons for casting is output.
Output must be formatted as a string, and so we may need to convert a certain piece of data to a string.
All input also comes as a string, and must then be converted to other data types.

Question 12

What are casting functions

Answer 12

Casting to a string can be done using the str function. E.g:
str(3) gives “3”.
Casting to an integer can be done using the int function. E.g:
int(3.4) gives 3.
Casting to a real can be done using the real function. E.g:
real(“3.4”) gives 3.4.

Question 13

What are the basic operators

Answer 13

Addition is done using a + sign.
Subtraction is done using a - sign.
Division is done using a / sign.
Multiplication is done using a * sign.
Exponentiation is done using a ^ sign.

Question 14

What’s a modulo operators

Answer 14

The modulo operator gives the remainder of the division of two numbers.
For example:
5 MOD 2 would be equal to 1.

Question 15

What’s integer division

Answer 15

The integer division operator returns the quotient (whole part) of a division.
For example:
5 DIV 2 would give 2.

Question 16

How do we test for comparisons

Answer 16

We can compare two numbers using the less than and greater than signs. For example:
2 < 3 evaluates to True.
2 > 3 evaluates to False.
We can test for less than or equal, or greater than or equal like this:
2 ≤ 3 evaluates to True.
3 ≥ 3 evaluates to True.

Question 17

How do you test for equality

Answer 17

We can test if two values are equal using the equality operator. For example:
2 = 2 would evaluate to True.
We can test if two values are not equal using the not-equal-to operator:
2 ≠ 2 would evaluate to False.

Question 18

What do ORs do

Answer 18

OR evaluates to True if any of the two operands are True:
True OR True = True.
True OR False = True.
False OR True = True.
False OR False = False.

Question 19

What do NOTs do

Answer 19

NOT negates a logical value.
NOT True = False.
NOT False = True

Question 20

What do ANDs

Answer 20

AND evaluates to True if and only if both operands are True.
True AND True = True.
True AND False = False.
False AND True = False.
False AND False = False.

Question 21

What happens in a sequence algorithm

Answer 21

In a sequence algorithm, the computer follows a series of steps that are executed in the same order every time it runs.
This is often not very useful for longer codes because we cannot use any selection or iteration structures

Question 22

What happens in a flow chart

Answer 22

The flow chart for a sequence program will have the blocks one by one.
One arrow will connect each block to the next block.
There will be no diamond shapes, so the diagram will be mainly:
Ovals.
Rectangles.
Parallelograms.

Question 23

What’s selection

Answer 23

Selection allows us to execute a section of code depending on whether a condition is met or not

Question 24

What’s Does an if statement do

Answer 24

An if-statement is an easy way of checking if a condition is true.

Question 25

What’s a switch case statement

Answer 25

A switch-case statement checks the value of a single variable

Question 26

What’s used to show selection in a flow diagram

Answer 26

The diamond symbol is used to show selection in a flow diagram.

Question 27

What’s definite iteration

Answer 27

A block of code will repeat a known number of times.

Question 28

What does a flow diagram use for iteration

Answer 28

A flow diagram for iteration uses the diamond shape

Question 29

What’s indefinite iteration

Answer 29

A block of code will repeat while a specified condition is true

Question 30

What are the advantages of subroutines

Answer 30

Easier to read:
There are fewer long blocks of code to understand.
More efficient:
Blocks of code can be written once and reused many times.
More reliable:
Each subroutine can be individually tested to make sure it works.

Question 31

What are parameters and arguments

Answer 31

Parameters are special variables used to pass values into a subroutine.
Arguments are the actual values that are passed in.

Question 32

What are the types of subroutines

Answer 32

A function is a subroutine which returns a value.

A procedure is a subroutine which does not return a value

Question 33

What’s a local scope

Answer 33

A variable defined within a subroutine will have local scope.
This means that they can only be accessed within that subroutine

Question 34

What’s a global scope

Answer 34

A variable can be made global by adding the ‘global’ keyword in front of it when it is first used.
Global variables may be accessed by any part of the whole program

Question 35

What are arrays

Answer 35

An array is a data structure that stores a fixed number of values under a single identifier.
The values must be of the same type.

Question 36

What are array elements

Answer 36

Each piece of data inside an array is called an element.
Each element has an index, which is its position within the array.
We start counting the indices from 0.

Question 37

What are arrays in pseudo code

Answer 37

An array of ten items can be created using the following syntax:
array name_of_array[10]
Values can be assigned as follows:
name_of_array[0] = "Hello"
Values can be accessed as follows:
OUTPUT name_of_array[0]

Question 38

What’s concatenation

Answer 38

Concatenation is joining two strings together.
This can be done with the + sign. E.g:
“Hello “ + “World” = “Hello World”.

Question 39

How do you asses a character

Answer 39

Remember, strings are just lists. So we can access a specific character in the exact same way as we access a list element:
string[3] would get the fourth character

Question 40

How do you know the length of a string

Answer 40

The length of a string is given by the len function:

len(“Hello”) would give 5.

Question 41

What’s a substring

Answer 41

A substring is a part of a longer string.
In pseudocode, we use the function:
substring(startPos, endPos, string)
This takes a substring starting at the ‘startPos’th character, and ending at the ‘endPos’th character.

Question 42

What are lists

Answer 42

Lists store multiple elements under the same identifier.

There can be a variable number of elements - they never get full

Question 43

What are list is in pseudocode

Answer 43

A list can be declared as follows:
pupils = []
Values can be added to the end of the list as follows:
pupils.append(“Alice”)
Values can be accessed as follows:
print(“The first student is “ + pupils[0])

Question 44

What’s a 2D list

Answer 44

A 2D list is a data structure where lists are filled with other lists.
This can be used to represent a 2D surface, or records.

Question 45

How do you access elements lists

Answer 45

To access an individual list, we can access the list as usual:
list = my2DList[4]
To access an individual element, we use this syntax:
list[5][0]
This would get the first element of the sixth list.

Question 46

What are the uses of 2D lists

Answer 46

2D lists are often used to represent a 2D surface, for example a chess board:
Each element of the 2D list could contain the chess piece in that location.
2D lists can be used to represent a database:
Each inner list can store a record of the database.
The outer list can store each record.

Question 47

What are text files

Answer 47

Text files consist of string data that can be read and processed by many applications

Question 48

What are files

Answer 48

Files allow us to store data so that it persists even when our program is not running.
This allows programs to ‘carry on where they left off’ when they are executed.

Question 49

What are binary files

Answer 49

Binary files consist of binary data that is read and processed by specific applications

Question 50

Why do we need to be carful when we access files

Answer 50

We must be careful with the way we access files so that we do not accidentally corrupt them

Question 51

How do we open files

Answer 51

First we open the file for use, so that the operating system knows that we are using it.
We can do this using:
openRead(“filename.txt”)
openWrite(“filename.txt”)

Question 52

How do we assign the variable

Answer 52

The file must be assigned to a variable so that we can keep refering to it.
This can be done as follows:
myFile = openRead(“filename.txt”)
myFile = openWrite(“filename.txt”)

Question 53

How do we read and write files

Answer 53

We can now read or write to the file using the following commands:
myFile.readLine() will return the next line of a file as a string.
myFile.writeLine() will write a line to the file.
myFile.endOfFile() will return True if we reach the end of the file

Question 54

Why do we close files and how

Answer 54

Finally, we must close the file so that it is free for another program to access.
We can do this using:
myFile.close()

Question 55

What does structured data refer to

Answer 55

any data that resides in a fixed field within a record or file so that it can be easily entered, stored, queried, and analysed

Question 56

What are records

Answer 56

Records are made up of fields.

For example, a person could be represented as a record where the fields include their name, age, and address

Question 57

What are Comma separated values (CSV) and what do they do

Answer 57

One method of storing a record is using comma separated values.
Each record is put on its own line.
Each field is separated by a special character such as a comma

Question 58

What are the pros and cons of records

Answer 58

Pros:
Very simple, text-based format.
Can be read by many applications.
Easy to use in programs.
Cons:
Inefficient for large datasets.
Can only store text data.
No built-in means of sorting or searching