Pointers are variables that store memory addresses. They can be used to point to other variables in memory and manipulate their values indirectly. The document discusses declaring pointer variables, pointer expressions, pointers with arrays, passing pointers to functions, and dynamic memory allocation using malloc(), calloc(), and realloc(). Pointers allow accessing and modifying values of other variables through memory addresses rather than direct variable names.

1. Presentation
of
C
Subject :- Pointers
Submitted to:-
Miss. Diya Sharma Submitted by :-
Lovepreet (023)
Grace (010)

2. Pointers
 Pointers are memory addresses variables i.e. the variables, which have
addresses of the variables having some value, stored in the memory.
 It represented as :
variable memory memory memory
name value address variable
q 280 6000 p
(pointer)

3. Declaring a Pointer Variable (Initialization of Pointer):
 A pointer variable should be declared before they are used. If a variables
going to hold a pointer, it must be declared as such. A pointer declaration
consists of a base type, an * , and variable name. base type define data
type………… its used in beginning of the main program.
 Syntax :-
data-type *pointer-variable ;
int *m; ,
float * y; ,
char * z; ……………….

4. Expressions
 An expression is a combination of operands and operators. It is a combination
of two or more than two operands or many operators.
 Example:- a+b*c/d and so on………….

5. Pointers expression
 Pointers deals with the arithmetic, relational, logical and assignment expressions.
Pointers are not directly used in the arithmetic, relational, logical and assignment
expression, only pointer values are used. Some of the arithmetic expression used
with pointer p1 and p2 as follow:
 Int x, y, *p1, *p2, z, a, b, c;
x = 10;
y = 20;
p1 = &x;
p2 = &y;
Z = (*p1)/(*p2);
a = (*p1)*(*p2);
b = (*p1)+(*p2);
c = (*p1)-(*p2);

6. Array
 Array is similar type of data collection name i.e. it is a collection of same
data type elements. An array is a group of related data items, which share
common name.
“It is the set of homogenous data”
a(0) a(1) a(3) a(4) or a{0., 1, 2, 3, 4}

7. Pointers with Array
 Pointers have close relationship with array. Pointers are linked with array
by taking its first element number and its base address. Suppose an array
of integer type, which is as defined as below:
 Static int a[5] = {25, 30, 35, 40, 45}
 Its can be represented in the computer memory as;
 a(0) a(1) a(2) a(3) a(4)
 Value address 25 30 35 40 45
 1000 1002 1004 1006 1008

8. Pointers and Function:
 We can pass pointer to the function and also pointer addresses can be
passed to the function as pointer arguments. This can be represented by
two ways…………..
 A). Pointer as function argument
 B) Pointer to function

9. Pointer as function argument
 1) Call by reference
 2) call by value
 swapping: exchanging of value from one variable to another……..
ex = X and Y

10. Dynamic Memory Allocation
 In dynamic memory allocation of the memory, the declaration of variable is
no longer required. The job of memory allocation can be done bye using the
three functions……
 1) maclloc():
 2) calloc():
 3) realoc():

11. 1). maclloc():
syntax = viod*maclloc(unsigned size);
2). calloc():
syntax = void*calloc(xyz, unsigned size);
3). realloc():
syntax = viod*realloc(void*block, unsigned size);