Programming Concepts (Cambridge (CIE) IGCSE Computer Science)

A data type is a classification of data into groups according to the kind of data they represent.

Integer is a data type used for whole numbers.

The Real data type represents numbers with a fractional part (decimal).

False.

The Character data type stores a single character.

The Boolean data type is used for true or false values.

Pi ← 3.142

Choosing the correct data type ensures accuracy and efficiency in the program.

String is a data type used for a sequence of characters.

False.

The Integer data type stores whole numbers only.

CHAR stores a single character, while STRING stores a sequence of characters.

An input is a value that is read from an input device and then processed by a computer program.

An output is a value sent to an output device from a computer program.

The keyboard is considered the standard for user input in programming.

True.

The monitor is considered the standard for user output.

INPUT Age

The OUTPUT command in pseudocode sends data to the screen.

False.

Inputs can be received from various devices including mice, sensors, and microphones.

Examples of output devices include:

monitors,

speakers,

printers.

When the INPUT command is executed, a program will wait for the user to type a sequence of characters.

Inputs are important because without them, programs can't interact with the outside world and always produce the same result.

Sequence refers to lines of code which are run one line at a time in the order that they are written.

False.

The order of instructions in a sequence is crucial to the flow of a program.

If instructions are out of sequence, it can lead to unexpected behaviour or errors.

Sequence is important because it determines the flow of a program and ensures instructions are executed in the correct order.

The first step in ensuring correct sequence is to plan the logical order of instructions before writing the code.

True.

In Python, indentation affects the sequence of code execution by defining code blocks.

The output would be:

1

The output would be:

13

Selection is when the flow of a program is changed, depending on a set of conditions.

An IF statement is a selection statement that allows you to execute a set of instructions if a condition is true.

The two ways to write selection statements are:

if... then... else...

and

case...

False.

IF statements do not always require an ELSE clause.

Nested selection is a selection statement within a selection statement, e.g., an If inside of another If.

A CASE statement is a selection statement used when comparing multiple values of the same variable.

False.

IF statements are more flexible and are generally used more in languages such as Python.

The purpose of selection in programming is to allow different code to be executed based on certain conditions.

IF <condition> THEN <statement> ENDIF

E.g.

IF Age < 18 THEN
OUTPUT "Too young"
ENDIF

IF-THEN statements execute code only if the condition is true, while IF-THEN-ELSE statements provide an alternative action if the condition is false.

Iteration is repeating a line or a block of code using a loop.

A count controlled loop is when the code is repeated a fixed number of times (e.g., using a for loop).

A condition controlled loop is when the code is repeated until a condition is met.

True.

FOR loops are always count controlled.

The two types of condition controlled loops are:

post-condition (REPEAT)

and

pre-condition (WHILE).

WHILE loops test the condition before executing the loop, while REPEAT loops execute the loop at least once before testing the condition.

Nested iteration is a loop within a loop, e.g., a FOR inside of another FOR.

Integer

FOR <identifier> ← <value1> TO <value2> <statements> NEXT <identifier>

E.g.

FOR Score ← 1 TO 10
....
NEXT Score

The STEP keyword in a FOR loop determines the increment or decrement value for each iteration.

Totalling involves adding up values, often in a loop.

Counting involves keeping track of the number of times a particular event occurs.

A total variable is typically initialised to 0 at the beginning of the program.

E.g.

Total ← 0

False.

While counting and totalling often occur in loops, they can also be done outside of loops.

A count variable is typically updated by incrementing it by 1 (Count ← Count + 1).

False.

A total variable can be used for various types of accumulation, not just adding numbers.

You would use totalling when you need to accumulate values, such as calculating a sum or average.

You would use counting when you need to keep track of occurrences, such as counting the number of times a condition is met.

String manipulation is the use of programming techniques to modify, analyse or extract information from a string.

Case conversion is the ability to change a string from one case to another, for example, lower case to upper case.

The LENGTH function counts the number of characters in a string.

False.

Substring extraction can start at any position within the string.

Slicing in string manipulation uses specific start and end positions to extract the desired characters from a string.

False.

In pseudocode, the first character of a string is at position 1.

UCASE converts a string to uppercase, while LCASE converts a string to lowercase.

Book ← "An Inspector Calls"

OUTPUT SUBSTRING(Book, 1, 3)

To count how many characters are in the password.

l J F
(with spaces)

An operator is a symbol used to instruct a computer to perform a specific operation on one or more values.

An arithmetic operator is a symbol used for mathematical operations such as addition, subtraction, multiplication, and division.

The modulus operator returns the remainder after division.

False.

In most programming languages, '=' is used for assignment, while '==' is used for comparison.

The three main Boolean operators are:

AND, OR, and NOT.

The AND operator returns True if both conditions are True.

True.

The OR operator returns True if at least one condition is True.

In Python, '/' performs floating-point division, while '//' performs integer division (quotient).

In pseudocode: ^, in Python: **.

The NOT operator returns the opposite of the condition (True if False, False if True).

A sub program is a sequence of instructions that perform a specific task or set of tasks.

A procedure is a type of sub program that performs a specific task but does not return a value.

A function is a type of sub program that performs a specific task and returns a value.

False.

Sub programs can be defined with or without parameters.

The purpose of using sub programs is to simplify a program by breaking it into smaller, more manageable parts and to avoid duplicating code.

You call a procedure in pseudocode using the CALL keyword,

E.g.

CALL Login

True.

Functions are always called within an expression because they return a value.

A function returns a value, whereas a procedure does not.

FUNCTION function_name(parameters)

....

RETURN ....

To 'call' a sub program means to execute it from the main program.

A local variable is a variable declared within a specific scope, such as a function or a code block.

False.

Local variables are accessible only within the block in which they are defined.

When the execution of the block ends, the local variable is destroyed and its memory is released.

A global variable is a variable declared at the outermost level of a program, outside any modules such as functions or procedures.

The scope of a global variable is global, meaning it can be accessed and modified from any part of the program.

False.

Local variables have a limited lifetime to the block in which they are defined, while global variables exist for the entire duration of the program.

global VariableName

The main difference between local and global variables in terms of accessibility is that local variables can only be accessed within their defined block, while global variables can be accessed from any part of the program.

Variable scope refers to the area of a program where a variable can be accessed and modified.

False.

In Python, you can access a global variable inside a function without using the 'global' keyword, but you need to use it if you want to modify the global variable.

Library routines are reusable code that can be used throughout a program, made public through reusable modules or functions.

False.

Using library routines saves programmers time by using working code that has already been tested.

The random library is a library of code which allows users to make use of 'random' in their programs, such as generating random choices or random numbers.

Random number generation is used to add an element of unpredictability in programs, such as simulating dice rolls, selecting random questions, or in cryptography.

In Python, you import the random library by using the statement:

import random

The randint() function in Python's random library generates a random integer within a specified range.

The round library is a library of code which allows users to round numerical values to a set amount of decimal places.

False.

The round function in Python can round to a specified number of decimal places.

The syntax for the round function in pseudocode is:

ROUND(<identifier>, <places>)

In Python, you would round 3.14159 to 2 decimal places using:

round(3.14159, 2)

The main goal is to make code easy to read using consistent techniques.

Layout refers to the spacing between sections of code, which helps improve readability and maintainability.

Indentation contributes to clearly defining sections of code, making it easier to read and maintain.

Comments are explanations of key parts of the code, which help other programmers understand the code's purpose and functionality.

False.

Using meaningful variable names that describe what is being stored improves code maintainability.

White space refers to adding suitable spaces in the code to make it easier to read and understand.

Sub-programs are functions or procedures used where possible to organise and modularise code, making it more maintainable.

True.

When consistency is applied in coding techniques, programs are easier to maintain.