7.1 Programming Techniques (OCR A Level Computer Science) Flashcards

The multiplication operator (*) is used to multiply numerical values together.

False.

The division operator (/) returns the quotient, not the remainder. The modulus operator (MOD) returns the remainder.

A logical operator is a symbol or keyword used to compare values and return a boolean result.

True.

The equal to operator (==) compares two values and returns true only when they are equal.

The not equal to operator (!=) returns true if two values are not equal, and false if they are equal.

The greater than (>) operator compares two values and returns true if the left operand is greater than the right operand.

A Boolean operator is a symbol or keyword used to combine and manipulate boolean values through logical operations such as AND, OR, and NOT.

True.

The AND operator requires both operands to be true for the result to be true; otherwise, it returns false.

The OR operator returns true if at least one of the operands is true, and false only if both operands are false.

The NOT operator negates a Boolean value, returning true if the operand is false and false if the operand is true.

A programming construct is a feature of a programming language that determines the order in which lines of code are executed.

The three main programming constructs are sequence, iteration and branching (selection).

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

Branching, or selection, is when the flow of a program is interrupted and a condition is tested, determining which lines or block of code are run next.

The keywords if, elseif, else, endif, switch, case indicate that the construct is selection.

False.

Iteration can be count controlled (a fixed number of times) or condition controlled (repeats until a condition is met).

Iteration is repeating a line or block of code using a loop, which can be count controlled or condition controlled.

Iteration is used to go through each number in the list (using a for loop), and selection (using if statements) is used to compare numbers and update the largest value found.

Selection is the use of branching programming constructs to test conditions, where the outcome determines which lines or blocks of code are run next.

The two main types of selection statements are if...elseif...else and switch...case.

A condition in selection is like asking a yes/no or Boolean question.

True.

Boolean operators allow multiple conditions to be tested together in selection statements.

An if statement is a conditional statement that runs a block of code only if a specified condition is true.

The if... else... statement allows a program to execute one block of code if a condition is true and another block if it is false.

An elseif clause allows you to check additional conditions if the initial if statement is false, enabling multiple decision branches.

In pseudocode, the if statement uses the keywords if and endif to start and end the block.

True.

You can include multiple elseif clauses to handle more than two possible outcomes in decision making.

If none of the if or elseif conditions are true, the else block is executed.

A switch/case statement is a type of conditional statement that performs multiple comparisons based on the value of an expression.

False.

Switch/case statements are most useful when you have a single expression to compare against multiple possible values.

The switch keyword is followed by an expression, which is compared against multiple case labels.

The default keyword specifies a block of code to execute if none of the case labels match the expression in a switch/case statement.

Iteration is the process of doing something more than once (repeat), also known as a loop.

A count controlled loop repeats code a fixed number of times, while a condition controlled loop repeats until a condition is met.

A count controlled loop is a loop that repeats a fixed number of times, whereas a condition controlled loop is a loop that repeats until a condition is met.

False.

A for loop is a count controlled loop, not a condition controlled loop.

A for loop is a count-controlled loop that repeats a fixed number of times, providing a concise way to perform repetitive tasks.

The three main parts are initialisation, range and increment/decrement.

A for loop is used to repeat a set of instructions a fixed number of times.

False.

In Python, the final number in range() is not included in the loop.

A while loop is a condition controlled loop that repeats until its condition becomes false. The condition is evaluated before each iteration.

False.

If the condition is false the first time it is checked, the while loop will not execute its code block at all.

A while loop is useful when the number of iterations is unknown in advance.

The output is: 30 goes into 100 3 times.

A do while loop is a type of condition controlled loop that always executes its code block at least once before checking the condition to continue or terminate.

False.

A while loop may not run at all if the condition is already met, unlike a do while loop which always executes its code block once before checking the condition.

In a do while loop, the code block is executed before evaluating the condition.

The main difference is that a do while loop always executes its code block at least once before checking the condition, whereas a while loop checks the condition first and may not execute the code block at all if the condition is already met.

Modularity is a concept where problems are broken down into more manageable pieces, with each piece handled by a single subroutine, promoting code reusability, modularity, and organisation.

A subroutine is a standalone block of code, also known as a module, that performs a specific task when called within a program.

A function returns a value, while a procedure does not return a value.

True.

Descriptive names for functions and parameters help make code easier to understand and maintain.

A function in programming pseudocode is a reusable block of code that performs a specific task, can take parameters, and may return a value.

The syntax for defining a function in pseudocode starts with the keyword function and ends with endfunction.

Parameters allow a function to receive input values so it can perform its task using different data each time it is called.

False.

In pseudocode, a function may or may not return a value, depending on how it is defined.

A procedure is similar to a function but does not return a value. It performs a series of actions or operations instead.

False.

A procedure does not return a value. It performs actions with or without a return statement, but no value is returned.

In pseudocode, a procedure is defined using the word procedure, followed by the procedure name and parameters.

Since addNumbers is a procedure and does not return a value, the variable c will not receive the result of the addition. The result is printed, not returned.

A parameter is a piece of data that is input into a code block such as a function or procedure so it can complete its task.

Passing a parameter into a code block allows the code block to use the input data to complete its task.

When passing parameters into a code block, two standard methods are used: passing by value (byVal) and passing by reference (byRef).

False.

Passing a parameter by value means a copy of the data is passed, so changes inside the function do not affect the original data outside.

Parameter passing by value means that a copy of the actual value is made and assigned to the function's parameter.

False.

When passing by value, any changes to the parameter within the function do not affect the original value outside the function.

This approach ensures that the original data remains unchanged, making it suitable when you want to protect the original data from being modified within the function.

Passing large data structures by value can lead to performance overhead because a copy of the data is made.

Parameter passing by reference is when a function receives the memory address of a value, allowing the function to directly modify the original data outside the function.

When a parameter is passed by reference, the function receives the memory address of the value, not a copy.

Passing parameters by reference can lead to unexpected side effects because changes made inside the function directly affect the original value outside the function.

True.

Passing by reference is often more efficient for large data structures because it avoids copying all the data.

Passing by value is when a function receives a copy of the argument's value, so changes to the parameter do not affect the original data.

Passing by reference is when a function receives a reference or memory address of the argument, allowing it to directly access and modify the original data.

False.

Passing by reference is more memory efficient for large data structures because it avoids making copies of the data.

Passing by value protects the original data from being modified within the function, while passing by reference allows direct modification of the original data.

Recursion is a programming technique where a function calls itself to solve a problem, using self-reference to break down complex problems into manageable subproblems.

A recursive algorithm must call itself, have a base case that allows it to return a value without further recursion, and a stopping base that is reachable after a finite number of calls.

A recursive function must have a base case to avoid stack overflow errors.

False.

Recursive functions do not use iterative loops; instead, they solve problems by repeatedly calling themselves with modified parameters until a base case is reached.

Recursion is a method where a function calls itself in order to solve a problem by breaking it down into smaller instances of the same problem.

Recursive code can be more concise and easier to read for certain problems, but is often harder to debug.

True.

Iteration uses less memory than recursion because it does not involve repeated function calls and stack usage.

Iteration is a method where a set of instructions is repeated using loops until a condition is met, often with better performance than recursion.

A recursive algorithm is an algorithm that calls itself repeatedly with modified parameters until a stopping condition is met.

A stopping condition prevents a recursive function from calling itself forever by providing a point where the recursion ends.

The recursive function countdown_rec(n) prints the current value, checks if n is 0, and if not, it calls itself with n - 1.

False.

When n reaches 0, the stopping condition is met and the function returns, ending the recursion.

Tracing a recursive algorithm like countdown_rec(n) helps us understand the sequence of function calls and how the program executes each step, making it easier to follow its logic and debug errors.

A trace table is a tool used to record the values of variables and function calls at each step of a program's execution, especially useful for understanding recursive algorithms.

In the recursive function countdown_rec(n), the function will stop calling itself when n equals 0.

True.

The trace table records each function call as countdown_rec is called with decreasing values until it reaches 0.

A global variable is a variable declared at the outermost level of a program, outside any functions or procedures, and can be accessed and modified from any part of the program.

Two common uses for global variables are data sharing between modules and storing configuration settings or constants.

A global variable can be accessed from any part of the program because it has global scope.

False.

Using many global variables makes programs more difficult to maintain and test, because it is harder to track where variables are changed and to test modules independently.

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

True.

Local variables have a limited lifetime and their memory is automatically reclaimed when the block ends.

A local variable is accessible only within the block in which it is defined.

A benefit of using local variables is data encapsulation and hiding. A drawback is that excessive use in nested blocks can reduce code readability and cause memory overhead in loops or recursive functions.

A global variable is a variable that is declared outside of functions and can be accessed and modified by any function in the program.

True.

The global keyword is needed to modify a global variable inside a function in Python.

In the local variable version, the function add_world returns the modified string, which is then assigned back to local_string.

global_string is modified directly within functions using the global keyword, while local_string is modified by functions returning new values that are reassigned to the variable.

An Integrated Development Environment (IDE) is a software tool that provides programmers with a comprehensive platform to write, edit, compile, debug, and manage code efficiently.

The main purpose of an IDE is to streamline the software development process by providing features and tools that help programmers write, compile, debug, and manage their code efficiently.

IDEs can be either an app to download or a web-based platform.

IDLE is a basic IDE used for writing and running Python code. Replit is a web-based IDE that supports collaboration and multiple programming languages such as Python, JavaScript, and C++.

Replit allows programmers to write and run code as well as collaborate with other programmers online.

False.

Autocomplete and auto indent features in an IDE are useful for writing code, but are not useful for debugging code.

Syntax highlighting is an IDE feature that visually distinguishes elements of code, such as keywords, strings, and comments, by using different colours and styles to improve code comprehension and reduce syntax errors.

Autocomplete helps programmers by suggesting code completions as they type, reducing typing effort, preventing errors, and improving productivity.

The feature that automatically indents the code when starting a new line in a block is called auto indent.

False.

Comments are not executed by the program; they serve as documentation and explanations for programmers.

A breakpoint is a marker set in code to halt program execution at a specific line, allowing developers to inspect the program's state and variable values during debugging.

The variable watch window tool in an IDE allows developers to monitor variable values as the program runs.

A class is a blueprint for creating objects, defining the attributes and methods that the objects will have in Object Oriented Programming.

A constructor is a special method used to initialize objects of a class by assigning values to their attributes when they are created.

A car object in a class might have attributes such as manufacturer, model, price, mileage, and whether it is preowned.

Two useful methods for a car class are Accelerate (to make the car go faster) and honkHorn (to make the car honk its horn).

An object in Object Oriented Programming is an instance of a class that contains both attributes (data) and methods (functions).

In Python, a class is defined using the class keyword, and objects are created by instantiating the class.

A constructor is a special method used to initialise the attributes of an object when it is created.

True.

A class acts as a blueprint, so multiple objects (instances) can be created, each with their own attribute values.

A method in OOP is a function defined within a class that defines the behaviour or actions that objects of the class can perform.

A public method can be accessed from outside the class, while a private method can only be accessed from within the class it is defined in.

In Python, a method with a single leading underscore is considered private by convention.

False.

In Python, methods with a leading underscore are private by convention but can still be accessed and invoked from outside the class.

An attribute is a variable that is associated with a class or object, used to store data about that object.

Attributes in Python classes are defined using the self keyword, followed by the attribute name and its initial value inside the __init__ method.

In the Lizard class, the attributes are speed, mass, and size.

False.

In Java, attributes are often declared as private within a class to enforce encapsulation.

In object-oriented programming, inheritance is the mechanism by which a class can acquire the properties and behaviours (methods and attributes) of another class.

In Java, the keyword extends is used to indicate that one class inherits from another.

The super keyword is used to call the constructor of the parent class, allowing inherited attributes to be initialised properly.

In Python, a class inherits from another class by placing the parent class name in parentheses after the class name.

True.

A derived class inherits both methods and attributes from its parent class, unless access is restricted.

The main advantage of inheritance is code reuse: common functionality can be written once in a base class and reused by derived classes, reducing duplication.

A class that is inherited from is called the base (or parent) class, while the class that inherits is called the derived (or child) class.

A constructor is a special method used to initialise objects of a class. In inheritance, derived class constructors often call the parent class constructor to initialise inherited attributes.

Encapsulation is the concept of restricting direct access to some of an object's data or methods, usually by making attributes private and providing controlled access through public methods.

The main purpose of a getter method is to provide controlled access to the value of a private attribute in an object without allowing direct modification.

True.

Setter methods often include validation logic to ensure that only valid values are assigned to private attributes, enforcing controlled access.

Attributes are declared as private to restrict direct access from outside the class, thereby protecting the internal state of the object and enforcing encapsulation.

A get method is also known as a getter or accessor.

Setter methods are commonly used to set the value of an object's private attribute.

A setter method is a method used to update or modify the value of a private attribute in a class, often including validation logic to enforce certain conditions.

A getter method retrieves the value of a private attribute, while a setter method updates or modifies the value of a private attribute, often with validation.

Polymorphism is the ability of different object types to be accessed through the same interface, allowing the correct method to be called depending on the object's actual type at run-time.

Method overriding is when a subclass provides its own implementation of a method that is already defined in its superclass.

True.

Polymorphism enables the same method name to invoke different behaviors depending on the runtime type of the object.

In run-time polymorphism, a subclass overrides a method of its superclass, and the correct version is chosen at run-time.

To implement polymorphism, you need inheritance and method overriding.

The make_sound(animal) function demonstrates run-time polymorphism, as it calls the correct speak() method based on the actual type of the object passed.

In Python, method overriding is shown when a subclass defines a method with the same name as one in its superclass.

True.

In Java, a superclass reference can refer to a subclass object, which is fundamental to achieving polymorphism.