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Questions and Answers
What is the main purpose of using pointers in C++?
What is the main purpose of using pointers in C++?
Which of the following is a valid declaration of a pointer?
Which of the following is a valid declaration of a pointer?
Why is it necessary to initialize a pointer variable before use?
Why is it necessary to initialize a pointer variable before use?
What will occur if you attempt to store a pointer value in an integer variable without conversion?
What will occur if you attempt to store a pointer value in an integer variable without conversion?
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What is the function of the ampersand (&) operator in relation to pointers?
What is the function of the ampersand (&) operator in relation to pointers?
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What must match for a pointer variable to hold the address of another variable?
What must match for a pointer variable to hold the address of another variable?
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Which statement is true about a null pointer?
Which statement is true about a null pointer?
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What is a wild pointer in C++?
What is a wild pointer in C++?
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What does the asterisk (*) symbolize in the context of pointer variables?
What does the asterisk (*) symbolize in the context of pointer variables?
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Where does a pointer variable itself store its address in memory?
Where does a pointer variable itself store its address in memory?
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Study Notes
Functions and Pointers
- Functions are blocks of code performing a specific task.
- C++ allows programmers to define their own functions.
- Functions group code to perform a specific task and have a name.
- When invoked, a function executes the codes in its body.
Introduction to Pointers
- A pointer is a variable that stores the address of another variable.
- Pointer variable declaration:
type *variableName;(e.g.,int *a;) - C++ uses pointers for dynamic data structures (e.g., linked lists).
- Pointers allow fast access to and manipulation of data in arrays.
- Pointers enhance low-level hardware interaction.
- Pointers avoid redundant data replication.
Why use Pointers?
- Pointers store addresses (64 bits, x86-64).
- Data types (e.g., int = 32 bits) limit int variable storage of addresses.
- Incrementing a pointer shifts it to the next data item.
- Incrementing an int variable changes its numeric value.
- Pointer truncation occurs when an int value tries to store a pointer.
Common Pointer Declarations
-
int *p1;//Pointer to an integer variable -
double *p2;//Pointer to a double variable -
char *p3;//Pointer to a character variable -
float *p4;// Pointer to a float variable -
char *ptr[100];// Array of 100 pointers to char -
Variables should be initialized (mandatory).
- Example:
int a = 10;
- Example:
C Pointers – Operators
-
&(ampersand): Returns the memory address of a variable. -
%p(format specifier): Displays addresses in hexadecimal format. - Pointers are used to store and manipulate memory addresses.
Value at Address Operator
-
*(asterisk): Returns the value at the memory address stored in a pointer. - The asterisk is also known as the value-at-address operator.
- Used to access the data at the memory location pointed to by the pointer.
- Example:
int *p1; p1 = &a; int val = *p1;
Types of Pointers
-
Null Pointer: A pointer that doesn't point to valid memory.
- Initialized with
nullptr(modern C++) orNULL(older).
- Initialized with
-
Void Pointer: A generic pointer that can hold the pointer to any data type.
- Needs a cast to access the actual data.
-
Wild Pointer: An uninitialized pointer to arbitrary memory location.
- Undefined behavior, not safe to access.
Pointer Arithmetic
- Pointers can be incremented or decremented.
- Arithmetic on an address is relative to the size of the contained value.
- Incrementing/Decrementing a pointer:
pointer += sizeof(data_type). - Addition/Subtraction by a constant (e.g.,
ptr= ptr + 3):-
pointer += i * sizeof(data_type).
-
- Subtraction between two pointers:
-
(address in pointer1)-(address in pointer2))/sizeof(data_type). - Calculates the number of elements between the pointers
-
Dereferencing
- Dereferencing is retrieving the value stored at the memory location a pointer points to.
- Use the asterisk (*) operator:
*pointer. - Example:
int *ptr = &x; cout << *ptr << endl;(outputs the value of x)
Calling a Function
- In C++, you call a function by writing its name followed by parenthesis, as seen in a simple example,
hello().
Function Definition and Declaration
- A function's declaration tells the compiler about its name, return type and parameters.
- Example:
int max(int num1, int num2);
- Example:
- A function's definition provides its actual code body with variables.
- Example:
int max(int num1, int num2) {
if (num1 > num2) return num1;
else return num2
}
Advantages of Functions
- Facilitates program maintenance and enhancement.
- Programs become easily understandable.
- Code duplication and errors are minimized.
- Debugging is significantly easier.
- Functions can be used in multiple programs.
Function Types
-
No Arguments, No Return Value:
void function_name(). -
No Arguments, Return Value:
dataType function_name(). -
Arguments, No Return Value:
void function_name(arguments) -
Arguments & Return Value:
dataType function_name(arguments) - Function declarations are placed above the
mainfunction, or can be placed above themainfunction. Function definitions are usually placed after the main function body.
Passing Arrays to Functions
- To pass an array to a function, pass the array name (without indexes).
- In a function, the formal parameter should be of the array type.
- Function prototype should show that the argument is an array.
Passing Structures to Functions
- To pass a structure to a function, pass the structure variable's name.
Function with no arguments and no return values
- Function receives no data at all.
- No data transfer between the calling and the called functions.
Functions with arguments and no return values
- Called function receives data from the calling function.
Function with arguments and return values
- Called function receives data from the calling function.
- When a function returns a value, the calling function receives the data.
- There is a two-way data transfer between the calling function and the called function. This is commonly used to use the return values from a function in other calculations, conditional blocks, or other steps in a program.
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Description
Explore the basics of functions and pointers in C++. This quiz covers the definition, usage, and advantages of functions and pointers, emphasizing their roles in enhancing code efficiency and enabling dynamic data structures. Test your understanding of these fundamental concepts in C++ programming.
