paper 2

Flowchart

A diagram that shows the step by step instructions of an algorithm using standard symbols

Pseudocode

A method of writing up a set of instructions for a computer s program using plain English

What is the most common input device?

The keyboard

What command in Python allows user input?

Input

Example of an input statement

Input(“prompt”

Input(“prompt”)

What is the prompt?

A message displayed on a users screen before they input their answer

What is the output function in Python?

Print

Example of a print statement

Print(“ hello, world!”)

Output data must be a _____ before we can print it

String

If we want to print data which is not a string, then we must…

Cast it to a string

What are the data types?

• Boolean (true/false)

• Integers (whole numbers - 1,3,2828)

• Float (decimal numbers- 3.6 7.6288)

• String (text- “hello world”)

Data types determine

How data is stored and what you can do with it

Casting

The process of converting a value from one data type to another, such as turning a string into an integer or vice versa

All input’s must come out as a string and must be

Converted to other data types

Casting to a string can be done using what function?

The str function

Eg; str(3) gives “3”

Int(3.4) would result as

The number 3

Type coercion allows us to…

Operate on data of different types

When adding two numbers of different data types, type coercion…

Allows one of the types to be automatically cast so that the operation can be completed

When working with a float and an integer, the final result will be a

Float

When working with a string and an integer, the result will be a

String

What is a variable?

A named memory location that holds data that can change while a program is running

What is a constant?

A named memory location where the value remains unchanged throughout a programs execution

The value of a variable can ….

Change whilst a program is running

To use a variable, we give it an _____ and a _____

Identifier, value

Operators are

Symbols that represent a specific function within a program

Relational operators

Operators which compare two values and produce a true or a false result

Boolean operators

Operators which perform logical operations and always results in a true or false value

What does MOD do?

Gives the reminder of a division. Eg:

5 MOD 2=1

What does DIV do?

Returns the quotient (whole part) of the division, Eg:

5 DIV 2 = 2

3//2

1

3/2

1.5

What is the assignment operator

=

Selection

A programming construct where a program makes a decision to run a specific block of code based on a condition, which can either be true or false.

What are the methods of selection

Else, if, Elif statements

If statement

Conditions can be tested using this statement, for example:

If( x > 50 ):

Else statements

We can add an else statement after an IMF statement, for example:

Else:

This will only execute the following block of code if the condition is false.

Elif statements

These statements can be added between if and else blocks.

• they will execute the condition before it was false, and the condition following it is true.

Example of using an if statement

IF condition 1:

action 1()

Example of using an elf statement

Elif condition2:

Action2()

Example of using the else statement

Else:

action3()

Iteration

The process of repeating a set of instructions or code in a program, also known as a “loop”

Iteration techniques

• while loop

• Repeat until

• For

• Do while

A flow diagram for iteration uses a

Diamond shape

What is definite iteration?

• a block of code will repeat a known number of times

What is indefinite iteration?

• a block of code will repeat whilst a specified condition is true

What would an example of definite iteration be?

A for loop will execute an indented block for each value in a list of values

What would be an example of indefinite iteration?

A while loop will continue to execute an indented block of code while a certain condition is true

Example of a for loop

For i in range(0,10):

action1()

action2()

Example of a while loop

While condition:

action 1()

action 2()

Listing

A data structure which holds a finite, ordered collection of items under a single identifier

What’s the main difference between listing and arrays?

Lists can hold data values with differing data types whereas arrays tend to elements of the same data type

list example

my_list = [1, "apple", True]  # works fine

• it holds multiple data types

Array example

my_array = array.array('i', [1, 2, 3])

• ‘i’ indicates integer

What do we use to add to an array?

Append

Example code for adding to an array

Myarr.append()

What would list[5].append(3) do?

Add 3 to the 6th inner list

The [5] would be the sixth list because

0 1 2 3 4 5 is six values altogether

What are the uses of 2D lists/arrays?

To represent a 2D surface, for example- a chess board

code to access an individual list from a 2D list

List= my2Dlist[4]

List[5][0] would allow us…

To access an individual element, this would give us the first element [0] of the sixth list [5]

2D list/array

A data structure where lists are filled with other lists

What is abstraction?

the process of simplifying a problem by removing all unnecessary details to focus only on the essential ones

What is defragmentation?

the process of reorganizing data on a hard disk drive so that all the fragments of a file are stored in a single, contiguous block of space

Whats the point of casting?

to convert data types for operations