Function Definitions and Anatomy

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Questions and Answers

Which of the following best describes a function?

  • A single value stored in memory.
  • A collection of statements grouped to perform an operation. (correct)
  • A data structure used to store related information.
  • A collection of variables of the same type.

What constitutes the function signature in C++?

  • The function name only.
  • The combination of the function name and parameter list. (correct)
  • The return type of the function.
  • The parameter list only.

What is another term of actual parameter?

  • Function Signature
  • Formal Parameter
  • Argument (correct)
  • Return Type

In the provided code snippet, what does '4' represent?

int max(int num1, int num2) // 4

<p>Function signature (A)</p> Signup and view all the answers

What is the purpose of the return statement in a function?

<p>To exit the function and optionally return a value. (B)</p> Signup and view all the answers

Consider the following C++ code. What will be the output?

int main() {
    int i = 5;
    int j = 2;
    int k = max(i, j); 
    std::cout << "The maximum between " << i << " and " << j << " is " << k; 
    return 0;
}

int max(int num1, int num2) {
    if (num1 > num2)
       return num1;
    else 
       return num2; 
}

<p><code>The maximum between 5 and 2 is 5</code> (A)</p> Signup and view all the answers

What is the significance of a 'void' return type in a function definition?

<p>It means the function does not return a value. (C)</p> Signup and view all the answers

In C++, if a function is defined to take two double arguments but is called with an int and a double, what typically happens?

<p>The <code>int</code> argument is automatically converted to a <code>double</code>. (B)</p> Signup and view all the answers

What is the potential issue with the following function call, given the function definition double ApplyDiscount(double amount, double percentage)?

ApplyDiscount(storeRate, finalAmount);

<p>It may produce incorrect results due to parameter order mismatch. (A)</p> Signup and view all the answers

What is the main advantage of breaking a program into smaller functions?

<p>It improves code organization and reusability (D)</p> Signup and view all the answers

What is function overloading?

<p>Creating multiple functions with the same name but different parameters. (C)</p> Signup and view all the answers

Consider the following code. What will be the output?

#include <iostream>

void print(int num) {
    std::cout << "Integer number: " << num << std::endl;
}

void print(double num) {
    std::cout << "Double number: " << num << std::endl;
}

int main() {
    int x = 10;
    double y = 5.5;
    print(x);
    print(y);
    return 0;
}

<p>Prints <code>Integer number: 10</code> followed by <code>Double number: 5.5</code> (D)</p> Signup and view all the answers

Why might you use function prototypes in C++?

<p>To declare a function before it is called, allowing the compiler to know its signature. (C)</p> Signup and view all the answers

What is a function prototype?

<p>A function declaration without implementation. (B)</p> Signup and view all the answers

What is the purpose of default arguments in C++ functions?

<p>To provide default values for function parameters, allowing the function to be called with fewer arguments. (D)</p> Signup and view all the answers

Which of the following is the correct syntax for declaring a default argument in a C++ function?

<p>void func(int x = 0); (D)</p> Signup and view all the answers

Why should default arguments be the last parameters in a function's parameter list?

<p>It is a requirement of the C++ syntax to avoid ambiguity during function calls. (D)</p> Signup and view all the answers

What is a local variable?

<p>A variable defined inside a function. (A)</p> Signup and view all the answers

What determines the scope of a variable?

<p>The part of the program where the variable can be referenced. (A)</p> Signup and view all the answers

If a local variable with the same name is declared in two non-nesting blocks within the same function, is this valid in C++?

<p>Yes, because the scopes do not overlap. (D)</p> Signup and view all the answers

What is the default initial value of a global variable in C++ if it is not explicitly initialized?

<p>Zero. (D)</p> Signup and view all the answers

Consider the following code snippet:

void myFunction() {
    int localVar = 5;
}

What is the scope of localVar?

<p>Local to <code>myFunction()</code>. (A)</p> Signup and view all the answers

Consider the following code snippet:

int globalVariable = 5;

void myFunction() {
    // Code here
}

int main() {
    // Code here
    return 0;
}

What is the scope of globalVariable?

<p>Accessible throughout the program. (A)</p> Signup and view all the answers

What is the purpose of a static local variable?

<p>To preserve the value of a local variable between function calls. (A)</p> Signup and view all the answers

Consider the following C++ code. What will be the value of staticVar after the program executes?

#include <iostream>

void myFunction() {
    static int staticVar = 0;
    staticVar++;
    std::cout << "StaticVar inside myFunction(): " << staticVar << std::endl;
}

int main() {
    myFunction();
    myFunction();
    myFunction();
    return 0;
}

<p>3 (D)</p> Signup and view all the answers

In pass-by-value, what happens to the actual parameter when the formal parameter is modified inside the function?

<p>The actual parameter remains unchanged because the formal parameter is a copy. (D)</p> Signup and view all the answers

In pass-by-value, what are the relationship between the formal parameter and the actual parameter?

<p>They are independent variables. (D)</p> Signup and view all the answers

Consider the following code. Which of the following describes num's behaviour?

#include <iostream>
using namespace std;

void incrementByValue(int num) {
    num++; 
    cout << "Inside function - Value of num: " << num << endl;
}

int main() {
    int num = 5;
    incrementByValue(num);
    cout << "After function call - Value of num: " << num << endl;
    return 0;
}

<p><code>num</code> in <code>main()</code> remains unchanged after calling <code>incrementByValue</code>. (A)</p> Signup and view all the answers

What is a reference variable in C++?

<p>An alias for another variable. (A)</p> Signup and view all the answers

What is the purpose of using a reference variable as a function parameter?

<p>To allow the function to modify the original variable directly. (A)</p> Signup and view all the answers

Consider the following code snippet:

void incrementByReference(int &num) {
    num++;
}

int main() {
    int number = 5;
    incrementByReference(number);
    std::cout << number << std::endl;
    return 0;
}

What will be the output?

<p>6 (A)</p> Signup and view all the answers

In which of the following scenarios is it most appropriate to use pass-by-reference instead of pass-by-value?

<p>When you need the function to modify the original variable directly. (D)</p> Signup and view all the answers

What is the code difference between pass-by-value and pass-by-reference?

<p>Pass-by-reference uses &amp; (B)</p> Signup and view all the answers

What is the benefit of using const with reference parameters?

<p>It prevents the function from modifying the original variable, providing data protection. (C)</p> Signup and view all the answers

Given the declaration int max(const int& num1, const int& num2);, what does const int& signify?

<p>The parameter is a reference to a constant integer, ensuring the original value is not modified. (C)</p> Signup and view all the answers

Flashcards

Function

A collection of statements that are grouped together to perform an operation.

Function Signature

The combination of the function name and the parameter list.

Formal Parameters

Variables defined in the function header (definition).

Actual Parameter/Argument

The value passed to a parameter when a function is invoked (called).

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Void Function

A function that does not return a value

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Parameter Order Association

The order in which arguments are provided when calling a function matters.

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Global Variables

Variables declared outside all functions and accessible to all functions.

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Static Local Variables

Variables that are permanently allocated in memory.

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Passing by Value

The actual parameter and its formal parameter are different, independent variables.

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Reference Variable

A special type of variable which can be used as a function parameter to reference the original variable.

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Passing by Reference

The actual parameter and its formal parameter refer to the same variable.

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Function Overloading

Creating multiple functions with the same name, but with different parameters

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Function Prototype

A function declaration without implementation.

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Default Arguments

C++ allows you to declare functions with default argument values. The default values are passed to the parameters when a function is invoked without the arguments.

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Local Variable

A variable defined inside a function.

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Scope of Variable

Part of program where the variable can be referenced.

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Study Notes

  • Functions are a collection of statements grouped together to perform an operation.

Defining a Function

  • A function's signature is its name combined with its parameter list.
  • Formal parameters are the variables defined in the function header.
  • When a function is invoked, a value is passed to the parameter; this value is the actual parameter, also known as an argument.

Function Anatomy

  • The general structure of a function includes a return type, function name, and a parameter list within parentheses, followed by the function body enclosed in curly braces.
  • The function body contains code statements and a return statement to provide a value back to the caller.

Calling Functions

  • To use a function, you must define it first (specify the return type, name, and formal parameters).
  • When calling the function you “invoke” it, and you provide a value for each parameter (arguments).
  • A function call is, for instance, max(x, y) where x and y are the actual parameters/arguments
  • The values of variables in the main() function are passed to the max() function, and the return value is used in main().

Trace Function Invocation

  • When the max() function is called, the values of 'i' and 'j' from main() are passed to 'num1' and 'num2' in max(), respectively.

Call Stacks

  • A call stack illustrates the memory allocation during function calls, showing the flow of variable declaration and value assignments for both the calling and called functions.
  • The stack shows which function has been invoked.

Void Function

  • A function that doesn’t return a value (void function), is declared with the void keyword as its return type.
  • There is no return value given, only a return; statement is given.

Passing Parameters to Functions

  • When passing parameters, the order of the parameters passed to a function matters.
  • The parameter order association should be considered (pass parameters in the order they are declared to ensure correct assignment).

Passing Parameters by Value

  • A function can be defined to be passed by value or by reference.
  • With pass by value, also known as call by value, changes made in the function to the parameters do not affect the variables the arguments are derived from
  • int max(int num1, int num2) - parameters passed by value

Modularization and C Program Layout

  • Functions are useful for modularizing code, breaking tasks down into subtasks.

Function Overloading

  • C++ allows multiple functions to have the same name if their parameters differ (function overloading).
  • Overloading the max function allows it to work with int or double data types through separate function definitions.

Function Prototypes

  • Before a function is called, it must be declared.
  • One can ensure a function is declared by: placing the function declaration before all function calls, or declare a function prototype before the function is called.
  • A function prototype is a function declaration without implementation (the implementation can be given later).

Default Arguments

  • C++ allows definition of functions with default argument values.
  • Default values are used if no arguments are provided when the function is called.
  • Default arguments should be the last parameters in the parameter list.

Scope of Variables

  • A local variable is defined inside a function.

Global Variables

  • Global variables are declared (defined) outside all functions, making them accessible to any function in that file.
  • Local variables don't have default values, so they must be initialized before use.
  • Global variables are defaulted to zero upon declaration.

Static Local Variables

  • After a function completes its execution, all its local variables are destroyed.
  • C++ allows declaring static local variables.
  • It is desirable to retain the value stored in local variables so that they can be used in the next call.
  • Static local variables are permanently allocated in the memory for the lifetime of the program.
  • The keyword static is used to declare a static local variable.

Passing Parameters to Functions (Pass by Value vs. Pass by Reference)

  • When passing parameters to functions, two main methods exist: pass by value and pass by reference.

Pass By Value Summary

  • In pass-by-value, the actual parameter and its formal parameter are independent variables.

Note About Literals

  • A literal value is a value assigned to the variable such as (1,2,3...) for int or (1.5, 0.5, 3.5...) for float or double or other types.
  • The value of the variable is the literal value that assigned to the parameter.

Reference Variable

  • C++ provides a special type of variable called a reference variable.
  • They can be used as a function parameter to reference the original variable.
  • A reference variable is an alias for another variable.

Passing Parameters by Reference

  • You can use a reference variable as a parameter in a function and pass a regular variable to invoke the function.
  • When you change the value through the reference variable, the original value is actually changed.
  • Using & in the function parameter defines it to be passed by reference.
  • int max(const int& num1, const int& num2) : parameters passed by reference

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