Short Notes: Two Dimensional Arrays | Short Notes for Computer Science Engineering - Computer Science Engineering (CSE) PDF Download

 Page 1


TWO DIMENSIONAL ARRAYS
Arrays that we have considered up to now are one dimensional array, a single line of elements. 
Often data come naturally in the form of a table, e.g. spreadsheet, which need a two-dimensional 
array.
Declaration:
The syntax is same as for 1-D array but here 2 subscripts are used.
Syntax:
data type array_name[rowsize][columnsize];
Rowsize specifies the no.of rows Columnsize 
specifies the no.of columns.
Example:
int a[4][5];
This is a 2-D array of 4 rows and 5 columns. Here the first element of the array is a[0][0] and last 
element of the array is a[3][4] and total no.of elements is 4*5=20.
col 0 col 1 col 2 col 3 col 4
row 0
a[0][0]
a[0][1] a[0][2]
a[0][3]
a[0][4]
row 1 a[1][0] a[1][1] a[1][2] a[1][3] a[1][4]
row 2 a[2][0] a[2][1] a[2][2] a[2][3] a[2][4]
row 3
a[3][0]
a[3][1] a[3][2]
a[3][3]
a[3][4]
Initialization:
2-D arrays can be initialized in a way similar to 1-D arrays. 
Example:
int m[4][3]={1,2,3,4,5,6,7,8,9,10,11,12};
Page 2


TWO DIMENSIONAL ARRAYS
Arrays that we have considered up to now are one dimensional array, a single line of elements. 
Often data come naturally in the form of a table, e.g. spreadsheet, which need a two-dimensional 
array.
Declaration:
The syntax is same as for 1-D array but here 2 subscripts are used.
Syntax:
data type array_name[rowsize][columnsize];
Rowsize specifies the no.of rows Columnsize 
specifies the no.of columns.
Example:
int a[4][5];
This is a 2-D array of 4 rows and 5 columns. Here the first element of the array is a[0][0] and last 
element of the array is a[3][4] and total no.of elements is 4*5=20.
col 0 col 1 col 2 col 3 col 4
row 0
a[0][0]
a[0][1] a[0][2]
a[0][3]
a[0][4]
row 1 a[1][0] a[1][1] a[1][2] a[1][3] a[1][4]
row 2 a[2][0] a[2][1] a[2][2] a[2][3] a[2][4]
row 3
a[3][0]
a[3][1] a[3][2]
a[3][3]
a[3][4]
Initialization:
2-D arrays can be initialized in a way similar to 1-D arrays. 
Example:
int m[4][3]={1,2,3,4,5,6,7,8,9,10,11,12};
The values are assigned as follows:
m[0][0]:1
m[1][0]:4
m[0][1]:2
m[1][1]:5
m[0][2]:3
m[3][2]:6
m[2][0]:7 m[2][1]:8
m[3][2]:9
m[3][0]:10
m[3][1]:11
m[3][2]:12
The initialization of group of elements as follows
int m[4][3]=={{11},{12,13},{14,15,16},{17}};
The values are assigned as:
m[0][0]:1 1 m[0][1]:0 m[0][2]:0
m[1][0]:12
m[1][1]:13 m[3][2]:0
m[2][0]:14
m[2][1]:15
m[3][2]:16
m[3][0]:17
m[3][1]:0 m[3][2]:0
Note:
In 2-D arrays it is optional to specify the first dimension but the second dimension should always 
be present.
Example: int
m[][3]={
{1,10},
{2,20,200},
{3},
{4,40,400} };
Here the first dimension is taken 4 since there are 4 roes in the initialization list. A 2-D array is 
known as matrix.
Page 3


TWO DIMENSIONAL ARRAYS
Arrays that we have considered up to now are one dimensional array, a single line of elements. 
Often data come naturally in the form of a table, e.g. spreadsheet, which need a two-dimensional 
array.
Declaration:
The syntax is same as for 1-D array but here 2 subscripts are used.
Syntax:
data type array_name[rowsize][columnsize];
Rowsize specifies the no.of rows Columnsize 
specifies the no.of columns.
Example:
int a[4][5];
This is a 2-D array of 4 rows and 5 columns. Here the first element of the array is a[0][0] and last 
element of the array is a[3][4] and total no.of elements is 4*5=20.
col 0 col 1 col 2 col 3 col 4
row 0
a[0][0]
a[0][1] a[0][2]
a[0][3]
a[0][4]
row 1 a[1][0] a[1][1] a[1][2] a[1][3] a[1][4]
row 2 a[2][0] a[2][1] a[2][2] a[2][3] a[2][4]
row 3
a[3][0]
a[3][1] a[3][2]
a[3][3]
a[3][4]
Initialization:
2-D arrays can be initialized in a way similar to 1-D arrays. 
Example:
int m[4][3]={1,2,3,4,5,6,7,8,9,10,11,12};
The values are assigned as follows:
m[0][0]:1
m[1][0]:4
m[0][1]:2
m[1][1]:5
m[0][2]:3
m[3][2]:6
m[2][0]:7 m[2][1]:8
m[3][2]:9
m[3][0]:10
m[3][1]:11
m[3][2]:12
The initialization of group of elements as follows
int m[4][3]=={{11},{12,13},{14,15,16},{17}};
The values are assigned as:
m[0][0]:1 1 m[0][1]:0 m[0][2]:0
m[1][0]:12
m[1][1]:13 m[3][2]:0
m[2][0]:14
m[2][1]:15
m[3][2]:16
m[3][0]:17
m[3][1]:0 m[3][2]:0
Note:
In 2-D arrays it is optional to specify the first dimension but the second dimension should always 
be present.
Example: int
m[][3]={
{1,10},
{2,20,200},
{3},
{4,40,400} };
Here the first dimension is taken 4 since there are 4 roes in the initialization list. A 2-D array is 
known as matrix.
Processing:
For processing of 2-D arrays we need two nested for loops. The outer loop indicates the rows and 
the inner loop indicates the columns.
Example:
int a[4][5];
a) Reading values in a 
for(i=0;i<4;i++)
for(j=0;j<5;j++)
scanf(“%d” , &a[i][j]);
b) Displaying values of a 
for(i=0;i<4;i++)
for(j= 0;j<5;j++)
printf(“%d” ,a[i][j]);
Example 1:
Write a C program to find sum of two matrices 
#include <stdio.h>
#include<conio.h> 
void main()
{
float a[2][2], b[2][2], c[2][2]; 
int i,j; 
clrscr();
printf("Enter the elements of 1st matrix\n");
/* Reading two dimensional Array with the help of two for loop. I f there is an array of 'n' 
dimension, 'n' numbers of loops are needed for inserting data to array.*/ 
for(i=0;i<2;I+ +)
for(j= 0;j<2;j++)
{
scanf("%f', &a[i][j]);
}
printf("Enter the elements of 2nd matrix\n"); 
for(i=0;i<2;i++)
for(j= 0;j<2;j++)
{
Page 4


TWO DIMENSIONAL ARRAYS
Arrays that we have considered up to now are one dimensional array, a single line of elements. 
Often data come naturally in the form of a table, e.g. spreadsheet, which need a two-dimensional 
array.
Declaration:
The syntax is same as for 1-D array but here 2 subscripts are used.
Syntax:
data type array_name[rowsize][columnsize];
Rowsize specifies the no.of rows Columnsize 
specifies the no.of columns.
Example:
int a[4][5];
This is a 2-D array of 4 rows and 5 columns. Here the first element of the array is a[0][0] and last 
element of the array is a[3][4] and total no.of elements is 4*5=20.
col 0 col 1 col 2 col 3 col 4
row 0
a[0][0]
a[0][1] a[0][2]
a[0][3]
a[0][4]
row 1 a[1][0] a[1][1] a[1][2] a[1][3] a[1][4]
row 2 a[2][0] a[2][1] a[2][2] a[2][3] a[2][4]
row 3
a[3][0]
a[3][1] a[3][2]
a[3][3]
a[3][4]
Initialization:
2-D arrays can be initialized in a way similar to 1-D arrays. 
Example:
int m[4][3]={1,2,3,4,5,6,7,8,9,10,11,12};
The values are assigned as follows:
m[0][0]:1
m[1][0]:4
m[0][1]:2
m[1][1]:5
m[0][2]:3
m[3][2]:6
m[2][0]:7 m[2][1]:8
m[3][2]:9
m[3][0]:10
m[3][1]:11
m[3][2]:12
The initialization of group of elements as follows
int m[4][3]=={{11},{12,13},{14,15,16},{17}};
The values are assigned as:
m[0][0]:1 1 m[0][1]:0 m[0][2]:0
m[1][0]:12
m[1][1]:13 m[3][2]:0
m[2][0]:14
m[2][1]:15
m[3][2]:16
m[3][0]:17
m[3][1]:0 m[3][2]:0
Note:
In 2-D arrays it is optional to specify the first dimension but the second dimension should always 
be present.
Example: int
m[][3]={
{1,10},
{2,20,200},
{3},
{4,40,400} };
Here the first dimension is taken 4 since there are 4 roes in the initialization list. A 2-D array is 
known as matrix.
Processing:
For processing of 2-D arrays we need two nested for loops. The outer loop indicates the rows and 
the inner loop indicates the columns.
Example:
int a[4][5];
a) Reading values in a 
for(i=0;i<4;i++)
for(j=0;j<5;j++)
scanf(“%d” , &a[i][j]);
b) Displaying values of a 
for(i=0;i<4;i++)
for(j= 0;j<5;j++)
printf(“%d” ,a[i][j]);
Example 1:
Write a C program to find sum of two matrices 
#include <stdio.h>
#include<conio.h> 
void main()
{
float a[2][2], b[2][2], c[2][2]; 
int i,j; 
clrscr();
printf("Enter the elements of 1st matrix\n");
/* Reading two dimensional Array with the help of two for loop. I f there is an array of 'n' 
dimension, 'n' numbers of loops are needed for inserting data to array.*/ 
for(i=0;i<2;I+ +)
for(j= 0;j<2;j++)
{
scanf("%f', &a[i][j]);
}
printf("Enter the elements of 2nd matrix\n"); 
for(i=0;i<2;i++)
for(j= 0;j<2;j++)
{
scanf("%f,&b[i][j]);
}
/* accessing corresponding elements of two arrays. */ 
for(i=0;i<2;i++)
for(j=0;j<2;j++)
{
c[i][j]=a[i][j]+b[i][j]; /* Sum of corresponding elements of two arrays. */
}
/* To display matrix sum in order. */ 
printf("\nSum Of Matrix:"); 
for(i=0;i<2; ++i)
{
for(j= 0;j<2;++j)
Printf("0 % of', c[i][j]); 
printf("\n");
}
getch();
}
Example 2:_Program for multiplication of two matrices 
# include <stdio.h>
#include<conio.h> 
int main()
{ int i,j,k;
int row 1,col1,row2,col2,row3,col3;
int mat1[5][5], mat2[5][5], mat3[5][5];
clrscr();
printf(“\n enter the number of rows in the first matrix:” ); 
scanf(“%d” , &row1);
printf(“\n enter the number of columns in the first matrix: ” ); 
scanf(“%d” , &col1);
printf(“\n enter the number of rows in the second matrix:” ); 
scanf(“%d” , &row2);
printf(“\n enter the number of columns in the second matrix:” ); 
scanf(“%d” , &col2); 
if(col1 != row2)
{
printf(“\n The number of columns in the first matrix must be equal to the number of rows 
in the second matrix ” );
Page 5


TWO DIMENSIONAL ARRAYS
Arrays that we have considered up to now are one dimensional array, a single line of elements. 
Often data come naturally in the form of a table, e.g. spreadsheet, which need a two-dimensional 
array.
Declaration:
The syntax is same as for 1-D array but here 2 subscripts are used.
Syntax:
data type array_name[rowsize][columnsize];
Rowsize specifies the no.of rows Columnsize 
specifies the no.of columns.
Example:
int a[4][5];
This is a 2-D array of 4 rows and 5 columns. Here the first element of the array is a[0][0] and last 
element of the array is a[3][4] and total no.of elements is 4*5=20.
col 0 col 1 col 2 col 3 col 4
row 0
a[0][0]
a[0][1] a[0][2]
a[0][3]
a[0][4]
row 1 a[1][0] a[1][1] a[1][2] a[1][3] a[1][4]
row 2 a[2][0] a[2][1] a[2][2] a[2][3] a[2][4]
row 3
a[3][0]
a[3][1] a[3][2]
a[3][3]
a[3][4]
Initialization:
2-D arrays can be initialized in a way similar to 1-D arrays. 
Example:
int m[4][3]={1,2,3,4,5,6,7,8,9,10,11,12};
The values are assigned as follows:
m[0][0]:1
m[1][0]:4
m[0][1]:2
m[1][1]:5
m[0][2]:3
m[3][2]:6
m[2][0]:7 m[2][1]:8
m[3][2]:9
m[3][0]:10
m[3][1]:11
m[3][2]:12
The initialization of group of elements as follows
int m[4][3]=={{11},{12,13},{14,15,16},{17}};
The values are assigned as:
m[0][0]:1 1 m[0][1]:0 m[0][2]:0
m[1][0]:12
m[1][1]:13 m[3][2]:0
m[2][0]:14
m[2][1]:15
m[3][2]:16
m[3][0]:17
m[3][1]:0 m[3][2]:0
Note:
In 2-D arrays it is optional to specify the first dimension but the second dimension should always 
be present.
Example: int
m[][3]={
{1,10},
{2,20,200},
{3},
{4,40,400} };
Here the first dimension is taken 4 since there are 4 roes in the initialization list. A 2-D array is 
known as matrix.
Processing:
For processing of 2-D arrays we need two nested for loops. The outer loop indicates the rows and 
the inner loop indicates the columns.
Example:
int a[4][5];
a) Reading values in a 
for(i=0;i<4;i++)
for(j=0;j<5;j++)
scanf(“%d” , &a[i][j]);
b) Displaying values of a 
for(i=0;i<4;i++)
for(j= 0;j<5;j++)
printf(“%d” ,a[i][j]);
Example 1:
Write a C program to find sum of two matrices 
#include <stdio.h>
#include<conio.h> 
void main()
{
float a[2][2], b[2][2], c[2][2]; 
int i,j; 
clrscr();
printf("Enter the elements of 1st matrix\n");
/* Reading two dimensional Array with the help of two for loop. I f there is an array of 'n' 
dimension, 'n' numbers of loops are needed for inserting data to array.*/ 
for(i=0;i<2;I+ +)
for(j= 0;j<2;j++)
{
scanf("%f', &a[i][j]);
}
printf("Enter the elements of 2nd matrix\n"); 
for(i=0;i<2;i++)
for(j= 0;j<2;j++)
{
scanf("%f,&b[i][j]);
}
/* accessing corresponding elements of two arrays. */ 
for(i=0;i<2;i++)
for(j=0;j<2;j++)
{
c[i][j]=a[i][j]+b[i][j]; /* Sum of corresponding elements of two arrays. */
}
/* To display matrix sum in order. */ 
printf("\nSum Of Matrix:"); 
for(i=0;i<2; ++i)
{
for(j= 0;j<2;++j)
Printf("0 % of', c[i][j]); 
printf("\n");
}
getch();
}
Example 2:_Program for multiplication of two matrices 
# include <stdio.h>
#include<conio.h> 
int main()
{ int i,j,k;
int row 1,col1,row2,col2,row3,col3;
int mat1[5][5], mat2[5][5], mat3[5][5];
clrscr();
printf(“\n enter the number of rows in the first matrix:” ); 
scanf(“%d” , &row1);
printf(“\n enter the number of columns in the first matrix: ” ); 
scanf(“%d” , &col1);
printf(“\n enter the number of rows in the second matrix:” ); 
scanf(“%d” , &row2);
printf(“\n enter the number of columns in the second matrix:” ); 
scanf(“%d” , &col2); 
if(col1 != row2)
{
printf(“\n The number of columns in the first matrix must be equal to the number of rows 
in the second matrix ” );
getch();
exit();
}
row3= rowl; 
col3= col3;
printf(“\n Enter the elements of the first matrix” ); 
for(i=0;i<row1;i+ +)
{
for(j= 0;j<col1;j++)
scanf(“%d” , &mat1[i][j]);
}
printf(“\n Enter the elements of the second matrix” ); 
for(i=0;i<row2;i++)
{
for(j= 0;j<col2;j++)
scanf(“%d” , &mat2[i][j]);
}
for(i=0;i<row3;i++)
{
for(j= 0;j<col3;j++)
{
mat3[i][j]=0; 
for(k=0;k<col3;k+ +)
mat3[i][j] + =mat1[i][k]*mat2[k][j];
}
}
printf(“\n The elements o f the product matrix are ” ): 
for(i=0;i<row3;i++)
{
printf(“\n” );
for(j= 0;j<col3;j++)
printf(“\t %d” , mat3[i][j]);
}
return 0;
}
Output:
Enter the number of rows in the first matrix: 2