Arrays

 An Array is a collection of similar data items,
that are stored under a common name.
 Array might belonging to any of the data types
 Array size must be a constant value.
 Always, Contiguous(adjacent) memory
locations are used to store array elements in
memory.

 Stores the elements of same data type.
 Used for maintaining multiple variable names
using a single name.
 Used for sorting elements.
 Matrix operations can be performed using
arrays.
 Arrays are also used in CPU scheduling.

 Types
› One-Dimensional array
› Two-Dimensional array
› Multi-Dimensional array

 Array declaration:
› Syntax:
data_type array_name[size];
 Example: int x[3];
X[0]
X[1]
X[2]
x

 The initializer for an array is a comma-separated list of
constant expressions enclosed in braces ({ }).
 The initializer is preceded by an equal sign (=).
 It is not necessary to initialize all elements in an array. If an
array is partially initialized, elements that are not initialized
receive the value of the appropriate type.
 Array initialization can be made either :
› At compile time or
› At run time

 Syntax:
data_type array_name[size]={variables};
Example: int x[3]={5,3,7};
5
3
7
X[0]
X[1]
X[2]
x

 Array can also be initialized at the run time.
Example:
while(i<10)
{
if(i<5)
sum[i]=0;
else
sum[i]=sum[i]+i;
}
Example:
scanf(“%d%d”,&a[0],&a[1]);

#include<stdio.h>
#include<conio.h>
void main()
{
int x[2],i;
printf("nEnter the inputs:");
for(i=0;i<2;i++)
scanf("%d",&x[i]);
for(i=0;i<2;i++)
printf("nThe value in x[%d] is %d",i,x[i]);
getch();
}

Enter the inputs:3
6
The value in x[0] is 3
The value in x[1] is 6

#include<stdio.h>
#include<conio.h>
void main()
{
int i;
char x[5]={'a','b','c','d','e'};
clrscr();
for(i=0;i<5;i++)
printf("nThe value in x[%d] is %c",i,x[i]);
getch();
}

The value in x[0] is a
The value in x[1] is b
The value in x[2] is c
The value in x[3] is d
The value in x[4] is e

 Array declaration
› Syntax:
data_type array_name[row_size]
[col_size];
 Example: int x[3][2];
X[0][0]
X[1][0]
X[2][0]
Col 0 Col 1
row 0
row 1
row 2
X[0][1]
X[1][1]
X[2][1]

 Syntax:
data_type array_name[row_size]
[col_size]={variables};
 Example: int x[2][2]={1,50,2,75};

 int x[2][2]={ {1,50},
{2,75}
};
(or)
 int x[ ][2]={ {1,50},
{2,75}
};

 The array elements will be stored in
contiguous memory locations, and it is
illustrated below:
1 50
2 75
row 0
row 1
Col 0 Col 1

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j;
int x[2][2]={ {1,50},
{2,75}
};
clrscr();
for(i=0;i<2;i++)
for(j=0;j<2;j++)
printf("nThe value in x[%d][%d] is %d",i,j,x[i][j]);
getch();
}

The value in x[0][0] is 1

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j;
int x[][2]={ {1,50},{2,75},{3,65}};
clrscr();
for(i=0;i<=2;i++)
for(j=0;j<2;j++)
printf("nThe value in x[%d][%d] is %d",i,j,x[i][j]);
getch();
}

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j,k,r1,r2,c1,c2;
int a[5][5],b[5][5],c[5][5];
clrscr();
step1:
printf("n Enter the size of matrix A:");
scanf("%d%d",&r1,&c1);
printf("n Enter the size of matrix B: ");
if((c1==c2)&&(r1==r2))
goto step2;
else
goto step1;

step2:
printf("n Enter the elements of matrix A n");
for(i=0;i<r1;i++)
{
for(j=0;j<c1;j++)
{
scanf("%d",&a[i][j]);
}
}
printf("n Enter the elements of matrix B n");
for(i=0;i<r2;i++)
{
for(j=0;j<c2;j++)
{
scanf("t%d",&b[i][j]);
}
}

for(i=0;i<r1;i++)
{
for(j=0;j<c1;j++)
{
c[i][j]=0;
c[i][j]=c[i][j]+a[i][j]+b[i][j];
}
}
printf("n The resultant matrix after addition of A & B isn");
for(i=0;i<r1;i++)
{
for(j=0;j<c1;j++)
printf("%dt",c[i][j]);
printf("n");
}
getch();
}

Enter the size of matrix A: 2
2
Enter the size of matrix B: 2
2
Enter the elements of matrix A
2
2
2
2
Enter the elements of matrix B
3
3
3
3
The resultant matrix after addition of A&B is
5 5
5 5

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j,k,r1,r2,c1,c2;
int a[5][5],b[5][5],c[5][5];
clrscr();
step1:
printf("n Enter the size of matrix A n");
printf("n Enter the size of matrix B n");
if(c1==r2)
goto step2;
else
goto step1;

for(i=0;i<r1;i++)
{
for(j=0;j<c2;j++)
{
c[i][j]=0;
for(k=0;k<c1;k++)
{
c[i][j]=c[i][j]+a[i][k]*b[k][j];
}
}
}
for(i=0;i<r1;i++)
{
for(j=0;j<c2;j++)
printf("%dt",c[i][j]);
printf("n");
}
getch();
}

Enter the size of matrix A:2
2
Enter the size of matrix B:2
2
4
4
4
4
4
4
4
4
The resultant matrix is
32 32
32 32

Enter the size of matrix A:2
3
Enter the size of matrix B:3
2
1
2
3
4
5
6
2
4
6
8
2
4
The resultant matrix is
20 32
50 80

 An array can be passed as a parameter to a function by
specifying the array's name without an index.
 Here an array is transferred as parameter to a function.
void main() void fun(n,b[])
{ {
void fun(int,int); int x,b[5];
int a[5],n; …………..
…………… …………..
fun(n,a);
…………… }
}

#include<stdio.h>
#include<conio.h>
void add(int,int b[]);
void main()
{
int a[5],i,n;
clrscr();
printf("n Enter the Number: ");
scanf("%d",&n);
printf("n Enter the Values: ");
for(i=0;i<n;i++)
scanf("%d",&a[i]);
add(n,a);
}

void add(int x,int b[])
{
int sum=0,i;
for(i=0;i<x;i++)
sum=sum+b[i];
printf("nThe sum is: %d",sum);
}

Enter the Number: 5
Enter the Values: 1
2
3
4
5
The sum is: 15

 In an array the characters are terminated by
the null (‘0’) character.
 Example: char a[]={a,b,c};
a b c 0

#include<stdio.h>
#include<conio.h>
void main()
{
int i=0;
char a[]="abcd";
clrscr();
while(a[i]!='0')
{
printf("t%c",a[i]);
i++;
}
}

 Arrays can have more than one dimension, these arrays-of-
arrays are called multidimensional arrays.
 Here is the general form of a multidimensional array
declaration:
datatype array_name [size1][size2]….[size n]
datatype - type of the data.
array_name -name of the array.
size -size of the array.

 They are very similar to standard arrays with
the exception that they have multiple sets of
square brackets after the array identifier.
 A two dimensional array can be thought of as a
grid of rows and columns.
 A two-dimensional array is an example in this
section, although the techniques can be
extended to three or more dimensions.
 The simplest form of the multidimensional array
is the two-dimensional array.

Example:
int a[3][3][3];
Col 0 Col 1 Col 2
row 0
row 1
row 2
X[0][0]
X[1][0]
X[2][0]
X[0][1]
X[1][1]
X[2][1]
X[0][2]
X[1][2]
X[2][2]

Arrays

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