Array, string and pointer

ARRAY, STRING AND
POINTER
Unit 3

ARRAY
An array is a sequential collection of variables
of same data type which can be accessed using
an integer as index, that generally starts from
0. It stores data elements in a continuous
memory location. Each element can be
individually referenced with its respective
index.

…
1-Dimensional array: It is a linear array that stores
elements in a sequential order. Let us try to
demonstrate this with an example: Let us say we have
to store integers 2, 3, 5, 4, 6, 7. We can store it in an
array of integer data type. The way to do it is:
Declaration:
dataType nameOfTheArray [sizeOfTheArray];
int Arr[6];
Here Arr is the name of array and 6 is the size. It is necessary to define
the size array at compile time.

…
To store the above elements in the array:
dataType nameOfTheArray [ ] = {elements of array };
int Arr [ ] = { 2, 3, 5, 4, 6, 7 };
Since, the indexing of
an array starts from 0,
if the 4th element
needs to be accessed,
Arr [ 3 ] will give you
the value of the 4th
element. Similarly, nth
element can be
accessed by Arr[n-1].

…
#include<stdio.h>
int main(void)
{
int a[5];
a[0]=9;
a[1]=10;
a[2]=14;
a[3]=76;
a[4]=34;
for(int i=0; i<5;
i++)
{
printf("%d",a[i]);
}
#include<stdio.h>
int main(void)
{
int
a[5]={9,4,22,18,17};
for(int i=0; i<5; i++)
{
printf("%d",a[i]);
}
}

…
#include<stdio.h>
int main(void)
{
int a[5];
printf("Enter the 5 values:
");
for(int i=0; i<5; i++)
{
scanf("%d",&a[i]);
}
for(i=0; i<5; i++)
{
printf("nThe Values are:
%d",a[i]);
}

WHY ARRAY STARTS FROM ‘0’
5000 + 0 (Index) * 2(Size of Datatype
INT)
= 5000
INT)
= 5002
INT)
= 5004
Float)
= 5000
Float)
= 5004
5000 + 2 (Index) * 4(Size of Datatype = 5008
For INT Data Type
For FLOAT Data Type

STRING
In C, string is stored in an array of characters.
Each character in a string occupies one location in an
array. The null character '0' is put after the last character.
This is done so that program can tell when the end of
the string has been reached.
char c[] = “any name";
When the compiler encounters a sequence of characters
enclosed in the double quotation marks, it appends a null
character 0 at the end by default.

DECLARATION
char s[5];
Here, we have declared a string of 5 characters.
Initialization
char c[] = "abcd";
char c[50] = "abcd";
char c[] = {'a', 'b', 'c', 'd', '0'};
char c[5] = {'a', 'b', 'c', 'd', '0'};

EXAMPLE
#include <stdio.h>
void main ()
{
char a[7] = { ‘e’, ‘x’, ‘a’, ‘m’, ‘p’, ‘l’, ’e’ };
char b[10];
printf (“Enter the value for B”);
scanf("%s",b);
printf ("A Output: %sn", a);
printf ("B Output: %sn", b);
}

STRING FUNCTIONS
1. strlen("name of string")
2. strcpy( dest, source)
3. strcmp( string1, string2 )
4. strstr( str1, str2 )

STRING COPY AND LENGTH
#include <stdio.h>
#include <string.h>
Int main ()
{
char a[7] = { 'n', 'i', 's', 'h', 'a', 'n' };
char b[10]; int c; //scanf("%s",a);
printf ("A Output: %sn", a);
strcpy(b, a); c=strlen(b);
printf ("B Output: %sn", b);
printf ("B Output: %dn", c);
return 0;
}

STRCMP( STR1 , STR2 );
This function is used to compare two strings "str1"
and "str2". this function returns zero("0") if the two
compared strings are equal, else some none zero
integer.
Return value
- if Return value if < 0 then it indicates str1 is less
than str2
- if Return value if > 0 then it indicates str2 is less
than str1
- if Return value if = 0 then it indicates str1 is equal to
str2

#include <stdio.h>
#include <string.h>
void main ()
{
char a[10];
char b[10];
int c;
printf ("nEnter the value for a: ");
scanf("%s",a);
printf ("nEnter the value for b: ");
scanf("%s",b);
if(strcmp(b, a)==0)
{
printf ("Strings are equal");
}
else
{
printf ("Strings are not equal");
}
}
Output:
Enter the value of a:
example
Enter the value of b:
example
Strings are equal.

STRSTR()
#include<stdio.h>
#include<string.h>
int main ()
{
char str1[55] ="This is a test string for testing";
char str2[20]="test";
char *p;
p = strstr (str1, str2);
if(p)
{
printf("string foundn" );
}
else printf("string not foundn" );
return 0;
}
Output:
String found

POINTERS
Pointers store address of variables or a memory
location.
datatype *var_name;
int *ptr;
// An example pointer "ptr" that holds address of an integer variable
or holds address of a memory whose value(s) can be accessed as
integer values through "ptr"

…
#include <stdio.h>
void main()
{
int x = 10;
int *ptr;
ptr = &x;
printf(“Value is : %d”,*ptr);
}
1) Since there is * in declaration, ptr
becomes a pointer varaible (a variable
that stores address of another variable)
2) Since there is int before *, ptr is
pointer to an integer type variable int
*ptr;& operator before x is used to get
address of x. The address of x is
assigned to ptr.

…
void main()
{
int *p;
int var = 10;
p= &var;
printf("Value of variable var is: %d", var);
printf("nValue of variable var is: %d",
*p);
printf("nAddress of variable var is: %d",
&var);
printf("nAddress of variable var is: %d",
p);
/* Pointer of integer type, this can hold
the * address of a integer type variable.
*/
/* Assigning the address of variable var to
the pointer * p. The p can hold the
address of var because var is * an integer
type variable. */
Output:
Value of variable var is: 10
Value of variable var is: 10
Address of variable var is: 0x7fff5ed98c4c
Address of variable var is: 0x7fff5ed98c4c
Address of pointer p is: 0x7fff5ed98c50

ASCII VALUES
1. The ASCII table has 128
characters, with values from
0 through 127.
2. Uppercase A has ASCII
value 65 in decimal .So
for Z ,the value is 90 in
decimal.
3. Lowercase a has ASCII
value 97 in decimal .So
for z ,the value is 122 in
decimal.
The following program gives the ASCII values :
#include <stdio.h>
int main()
{
int i;
for( i=0 ; i<=255 ; i++ ) /*ASCII values ranges
from 0-255*/
{
printf("ASCII value of character %d = %cn", i, i);
}
}

Array, string and pointer

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Array, string and pointer