Pointers allow programs to pass references to variables rather than copy their values. This document discusses pointers in C, including:
- Pointers contain memory addresses and can reference variables of any type.
- & returns an address and * accesses the value at an address.
- Pointers make passing large data structures efficient and allow sharing data between parts of a program.
- Pointers also enable dynamically allocating memory at runtime.
Pointers are among C’s most powerful, yet most difficult concepts to master. Some tasks like dynamic memory allocation done only by using pointers. So it is essential to learn pointers.
Pointers are a type of variable, just like int, double, etc., except instead of storing a value, they store a memory address of another variable.
Pointers are among C’s most powerful, yet most difficult concepts to master. Some tasks like dynamic memory allocation done only by using pointers. So it is essential to learn pointers.
Pointers are a type of variable, just like int, double, etc., except instead of storing a value, they store a memory address of another variable.
This Presentation gives you all knowledge about #CPointers, #PointersInC.
The given slides are as follows:
1. Introduction of Pointers.
2. Systems to create a pointer in C.
3. Valid Pointer Examples in C.
4. Graphical representation of address assigning in c using pointer.
5. 1st Sample program of pointers in C.
6. Types of Pointers
7. NULL Pointer in C (Types of Pointer)
8. void Pointer in C (Types of Pointer)
9. Wild Pointer in C (Types of Pointer)
10. Changing value of variable using pointer
11. Update and Access value of variable using pointer in example.
12. Types of format specifies to print address in different format.
13. Advantages of Pointer in C.
14. Disadvantages of Pointer in C.
15. Pointers with Array using Programs. #pointerwitharray
16. Another Example of #pointerwitharray.
17. Relationship Between Arrays and Pointers.
18. Relationship Between Arrays and Pointers explanation with diagram.
19. Pointers and String. #PointersAndString
20. Function with Array Parameters using pointers.
21. Passing Pointers to Function or Pointer argument function. #PointerWithFunction
An introduction to pointers and references in C++ (with elements of C++11 and C++14). The presentation introduces the readers to the concepts of pointers and references through the pragmatic need of writing a swap function between integers. Generic programming notions (e.g., type constructors) are adopted when useful for the explanation.
In computer science, a pointer is a programming language object, whose value refers to (or "points to") another value stored elsewhere in the computer memory using its memory address. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer.
This Presentation gives you all knowledge about #CPointers, #PointersInC.
The given slides are as follows:
1. Introduction of Pointers.
2. Systems to create a pointer in C.
3. Valid Pointer Examples in C.
4. Graphical representation of address assigning in c using pointer.
5. 1st Sample program of pointers in C.
6. Types of Pointers
7. NULL Pointer in C (Types of Pointer)
8. void Pointer in C (Types of Pointer)
9. Wild Pointer in C (Types of Pointer)
10. Changing value of variable using pointer
11. Update and Access value of variable using pointer in example.
12. Types of format specifies to print address in different format.
13. Advantages of Pointer in C.
14. Disadvantages of Pointer in C.
15. Pointers with Array using Programs. #pointerwitharray
16. Another Example of #pointerwitharray.
17. Relationship Between Arrays and Pointers.
18. Relationship Between Arrays and Pointers explanation with diagram.
19. Pointers and String. #PointersAndString
20. Function with Array Parameters using pointers.
21. Passing Pointers to Function or Pointer argument function. #PointerWithFunction
An introduction to pointers and references in C++ (with elements of C++11 and C++14). The presentation introduces the readers to the concepts of pointers and references through the pragmatic need of writing a swap function between integers. Generic programming notions (e.g., type constructors) are adopted when useful for the explanation.
In computer science, a pointer is a programming language object, whose value refers to (or "points to") another value stored elsewhere in the computer memory using its memory address. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer.
A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before you can use it to store any variable address.
There are few important operations, which we will do with the help of pointers very frequently. (a) we define a pointer variable (b) assign the address of a variable to a pointer and (c) finally access the value at the address available in the pointer variable. This is done by using unary operator * that returns the value of the variable located at the address specified by its operand.
Intro To C++ - Class 06 - Introduction To Classes, Objects, & Strings, Part IIBlue Elephant Consulting
This presentation is a part of the COP2272C college level course taught at the Florida Polytechnic University located in Lakeland Florida. The purpose of this course is to introduce students to the C++ language and the fundamentals of object orientated programming..
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Pratik Bakane C++ programs...............This are programs desingedby sy diploma student from Governement Polytecnic Thane.....programsare very easy alongwith coding andscreen shot of the output
COURSE TITLE: SOFTWARE DEVELOPMENT VI
COURSE CODE: VIT 351
TOPICS COVERED:
INTRODUCTION TO POINTERS
TYPES OF POINTERS
POINTERS EXAMPLES
POINTERS ARITHMETICS
ADVANTAGES AND DISADVANTAGES OF POINTERS
STATIC MEMORY ALLOCATION
DYNAMIC MEMORY ALLOCATION
QUIZ SET 3
1. Introduction to Pointers:
- Pointers are variables that store memory addresses. They provide a way to directly manipulate memory, enabling efficient and flexible programming.
2. Pointer to Pointer:
- A pointer that holds the address of another pointer. Useful in scenarios where multiple levels of indirection are required.
3. Null Pointer, Generic Pointer, and Dangling Pointer:
- Discusses the concepts of null pointers (pointers with no valid address), generic pointers (void pointers), and dangling pointers (pointers pointing to released memory).
4. Passing an Array to a Function:
- Explains how to pass arrays to functions, emphasizing the use of pointers to efficiently work with arrays in functions.
5. Returning an Array from Function:
- Explores the technique of returning arrays from functions, often involving the use of pointers to manage memory.
6. Array of Pointers:
- Describes the concept of an array where each element is a pointer, enabling the creation of dynamic data structures.
7. Pointers and 1D Array:
- Examines the relationship between pointers and one-dimensional arrays, highlighting how pointers can be used for array manipulation.
8. Pointers and 2D Array:
- Discusses the use of pointers in managing two-dimensional arrays, which involves handling rows and columns efficiently.
9. Using Pointers for String Manipulation:
- Illustrates how pointers are employed for efficient manipulation of strings, emphasizing dynamic memory allocation for flexible string handling.
10. Two-dimensional Array of Strings:
- Explores the combination of pointers and arrays to handle two-dimensional arrays of strings.
11. Array of Pointers to String:
- Focuses on the concept of an array where each element is a pointer to a string, allowing for dynamic string management.
At the end of this lecture students should be able to;
Define the C pointers and its usage in computer programming.
Describe pointer declaration and initialization.
Apply C pointers for expressions.
Experiment on pointer operations.
Identify NULL pointer concept.
Experiment on pointer to pointer, pointer arrays, arrays with pointers and functions with pointers.
Apply taught concepts for writing programs.
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Software Engineering, Software Consulting, Tech Lead.
Spring Boot, Spring Cloud, Spring Core, Spring JDBC, Spring Security,
Spring Transaction, Spring MVC,
Log4j, REST/SOAP WEB-SERVICES.
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2. What is a pointer
• In a generic sense, a “pointer” is anything that
tells us where something can be found.
– Addresses in the phone book
– URLs for webpages
– Road signs
3. 1/14/10
What is a pointer ?
• In C, a pointer variable (or just “pointer”) is
similar to a reference in Java except that
– A pointer can contain the memory address of any
variable type (Java references only refer to objects)
– A primitive (int, char, float)
– An array
– A struct or union
– Dynamically allocated memory
– Another pointer
– A function
– There’s a lot of syntax required to create and use
pointers
4. 1/14/10
Why Pointers?
• They allow you to refer to large data structures in a
compact way
• They facilitate sharing between different parts of programs
• They make it possible to get new memory dynamically as
your program is running
• They make it easy to represent relationships among data
items.
5. 1/14/10
Pointer Caution
• They are a powerful low-level device.
• Undisciplined use can be confusing and thus the
source of subtle, hard-to-find bugs.
– Program crashes
– Memory leaks
– Unpredictable results
6. 1/14/10
C Pointer Variables
To declare a pointer variable, we must do two things
– Use the “*” (star) character to indicate that the variable
being defined is a pointer type.
– Indicate the type of variable to which the pointer will
point (the pointee). This is necessary because C
provides operations on pointers (e.g., *, ++, etc) whose
meaning depends on the type of the pointee.
• General declaration of a pointer
type *nameOfPointer;
7. 1/14/10
Pointer Declaration
The declaration
int *intPtr;
defines the variable intPtr to be a pointer to a variable of
type int. intPtr will contain the memory address of some
int variable or int array. Read this declaration as
– “intPtr is a pointer to an int”, or equivalently
– “*intPtr is an int”
Caution -- Be careful when defining multiple variables on the
same line. In this definition
int *intPtr, intPtr2;
intPtr is a pointer to an int, but intPtr2 is not!
8. 1/14/10
Pointer Operators
The two primary operators used with pointers are
* (star) and & (ampersand)
– The * operator is used to define pointer variables and to
deference a pointer. “Dereferencing” a pointer means to
use the value of the pointee.
– The & operator gives the address of a variable.
Recall the use of & in scanf( )
9. 1/14/10
Pointer Examples
int x = 1, y = 2, z[10];
int *ip; /* ip is a pointer to an int */
ip = &x; /* ip points to (contains the memory address of) x */
y = *ip; /* y is now 1, indirectly copied from x using ip */
*ip = 0; /* x is now 0 */
ip = &z[5]; /* ip now points to z[5] */
If ip points to x, then *ip can be used anywhere x can be used so in this
example *ip = *ip + 10; and x = x + 10; are equivalent
The * and & operators bind more tightly than arithmetic operators so
y = *ip + 1; takes the value of the variable to which ip points, adds 1
and assigns it to y
Similarly, the statements *ip += 1; and ++*ip; and (*ip)++; all increment
the variable to which ip points. (Note that the parenthesis are
necessary in the last statement; without them, the expression would
increment ip rather than what it points to since operators like * and
++ associate from right to left.)
10. 1/14/10
Pointer and Variable types
• The type of a pointer and its pointee must match
int a = 42;
int *ip;
double d = 6.34;
double *dp;
ip = &a; /* ok -- types match */
dp = &d; /* ok */
ip = &d; /* compiler error -- type mismatch */
dp = &a; /* compiler error */
11. 1/14/10
More Pointer Code
• Use ampersand ( & ) to obtain the address of the pointee
• Use star ( * ) to get / change the value of the pointee
• Use %p to print the value of a pointer with printf( )
• What is the output from this code?
int a = 1, *ptr1;
/* show value and address of a
** and value of the pointer */
ptr1 = &a ;
printf("a = %d, &a = %p, ptr1 = %p, *ptr1 = %dn",
a, &a, ptr1, *ptr1) ;
/* change the value of a by dereferencing ptr1
** then print again */
*ptr1 = 35 ;
printf(“a = %d, &a = %p, ptr1 = %p, *ptr1 = %dn", a,
&a, ptr1, *ptr1) ;
12. 1/14/10
NULL
• NULL is a special value which may be assigned to a pointer
• NULL indicates that this pointer does not point to any
variable (there is no pointee)
• Often used when pointers are declared
int *pInt = NULL;
• Often used as the return type of functions that return a
pointer to indicate function failure
int *myPtr;
myPtr = myFunction( );
if (myPtr == NULL){
/* something bad happened */
}
• Dereferencing a pointer whose value is NULL will result in
program termination.
13. 1/14/10
Pointers and Function Arguments
• Since C passes all primitive function arguments “by value”
there is no direct way for a function to alter a variable in the
calling code.
• This version of the swap function doesn’t work. WHY NOT?
/* calling swap from somewhere in main() */
int x = 42, y = 17;
Swap( x, y );
/* wrong version of swap */
void Swap (int a, int b)
{
int temp;
temp = a;
a = b;
b = temp;
}
14. 1/14/10
A better swap( )
• The desired effect can be obtained by passing pointers to
the values to be exchanged.
• This is a very common use of pointers.
/* calling swap from somewhere in main( ) */
int x = 42, y = 17;
Swap( &x, &y );
/* correct version of swap */
void Swap (int *px, int *py)
{
int temp;
temp = *px;
*px = *py;
*py = temp;
}
15. 1/14/10
More Pointer Function
Parameters
• Passing the address of variable(s) to a function
can be used to have a function “return” multiple
values.
• The pointer arguments point to variables in the
calling code which are changed (“returned”) by
the function.
16. 1/14/10
ConvertTime.c
void ConvertTime (int time, int *pHours, int *pMins)
{
*pHours = time / 60;
*pMins = time % 60;
}
int main( )
{
int time, hours, minutes;
printf("Enter a time duration in minutes: ");
scanf ("%d", &time);
ConvertTime (time, &hours, &minutes);
printf("HH:MM format: %d:%02dn", hours, minutes);
return 0;
}
17. 1/14/10
An Exercise
• What is the output from this code?
void F (int a, int *b)
{
a = 7 ;
*b = a ;
b = &a ;
*b = 4 ;
printf("%d, %dn", a, *b) ;
}
int main()
{
int m = 3, n = 5;
F(m, &n) ;
printf("%d, %dn", m, n) ;
return 0;
}
4, 4
3, 7
18. 1/14/10
Pointers to struct
/* define a struct for related student data */
typedef struct student {
char name[50];
char major [20];
double gpa;
} STUDENT;
STUDENT bob = {"Bob Smith", "Math", 3.77};
STUDENT sally = {"Sally", "CSEE", 4.0};
STUDENT *pStudent; /* pStudent is a "pointer to struct student" */
/* make pStudent point to bob */
pStudent = &bob;
/* use -> to access the members */
printf ("Bob's name: %sn", pStudent->name);
printf ("Bob's gpa : %fn", pStudent->gpa);
/* make pStudent point to sally */
pStudent = &sally;
printf ("Sally's name: %sn", pStudent->name);
printf ("Sally's gpa: %fn", pStudent->gpa);
Note too that the following are equivalent. Why??
pStudent->gpa and (*pStudent).gpa /* the parentheses are necessary */
19. 9/24/10
Pointer to struct for functions
void PrintStudent(STUDENT *studentp)
{
printf(“Name : %sn”, studentp->name);
printf(“Major: %sn”, studentp->major);
printf(“GPA : %4.2f”, studentp->gpa);
}
Passing a pointer to a struct to a function is more
efficient than passing the struct itself. Why is
this true?