1. Arrays allow storing multiple values of the same data type under a single variable name. There are one-dimensional, two-dimensional, and multidimensional arrays. 2. One-dimensional arrays use a single subscript to store elements, two-dimensional arrays use two subscripts for rows and columns, and multidimensional arrays can have three or more dimensions. 3. Arrays can be initialized at compile-time by providing initial values, or at run-time by assigning values with a for loop or other method.

1. UNIT III
CHAPTER 1- ARRAYS
REFERENCE: PROGRAMMING IN C BY BALAGURUSWAMY
MRS. SOWMYA JYOTHI, SDMCBM, MANGALORE

2. Array : Array is a derived data type.
• When it is necessary to store more than one value
under a variable, user can make use of array.
•An array is a fixed-size sequence collection of
elements of the same data type.
•It is simply a grouping of like-data type.

3. Different types of arrays :
There are three types of arrays. They are,
1. One dimensional array.
2. Two dimensional array.
3. Multidimensional array.

4. One dimensional array :
•A list of items can be given one variable name using
only one subscript and such a variable is called
a one dimensional array.
Example : int number[5];
• Here in the example, 5 value of the variable
number can be kept under the single variable
number.

5. Declaration of one dimensional array : Like any other
variable, arrays must be declared before they are used.
•The general form of array declaration is,
• type variable_name[size];
The type specifies the type of elements that will be contained
in the array, such as int, float etc. The size indicates the
maximum number of element that can be stored inside the
array.
For example,
float height[50];
This declares the height to be an array containing 50 real
numbers.

6. Two dimensional array :
•When by using an array, user can store two value,
each for a row and a column under a variable, the
array is then called a two dimensional array.
Here, user can use infinite number of rows and
columns.
Two dimensional arrays are declared as follows,
• type array_name[row size][column size];
•Eg: int a[3][4];

7. Multidimensional array :
•C allows arrays of three or more dimensions. The exact limit
is determined by the compiler.
•The general form of a multidimensional array is,
• type arrayname[s1][s2]......[sn];
Where sn is the size of the dimension.
For example,
• int survey[3][5][12]
survey is a three dimensional array declared to contain 180
integer type elements.

8. Initialization of one dimensional array :
After an array is declared, its elements must be
initialized. An array can be initialized either of the
following stages,
1. At compile time.
2. At run time.

9. Compile time initialization :
User can initialize the elements of an array in the same
way as the ordinary variables when they are declared. This
is compile time initialization.
The general form is as follows,
• type arrayname[size]={list of values};
The values in the list are separated by commas.
For example,
• int number[3]={0,0,0};
This will declare the variable number as an array of size 3
and will assign 0 to each element.

10. Run time initialization :
• An array can be explicitly initialized at run time. This approach is
usually applied for initializing large arrays. For example,
for(i=0;i<100;i=i+1)
{
if (i<50)
sum[i]=0.0;
else
sum[i]=1.0;
}
The first 50 elements of the array sum are initialized to zero while the
remaining 50 elements are initialized to 1.0 at run time.

11. Initialization of two dimensional array :
Like the one dimensional arrays, two dimensional arrays may be
initialized by following their declaration with a list of initial
values enclosed in braces.
For example,
int table[2][3]={0,0,0,1,1,1};
This initializes the elements of the first row to 0 and the second
row to 1. This statement can also be written as,
• int table[2][3]={{0,0,0}, {1,1,1}};
• This can also be written as,
int table[2][3]= {
{0,0,0},
{1,1,1}
};

12. marks [0][0]
35.5
Marks [0][1]
40.5
Marks [0][2]
45.5
marks [1][0]
50.5
Marks [1][1]
55.5
Marks [1][2]
60.5
marks [2][0] Marks [2][1] Marks [2][2]
marks [3][0] Marks [3][1] Marks [3][2]
Elements of multi dimension arrays:
A 2 dimensional array marks [4][3] is shown below figure.
The first element is given by marks [0][0] contains 35.5 &
second element is marks [0][1] and contains 40.5 and so on.

13. min=a[1] i.e min=36
i=2
a[2]< min 55<36 NO
i=3
A[3]< min 23<36 YES
min=23 SWAP
i=4
A[4]<min 12<23 YES
min=12 SWAP
i=5
A[5]<min 95<12 NO
1 2 3 4 5

14. max=a[1] i.e max=36
i=2
a[2]> max 55>36 YES
max=a[2] max=55 SWAP
i=3
A[3]>max 23>55 NO
max=55 No change in max
i=4
A[4]>max 12>55 NO
i=5
A[5]>max 95>55 YES
Max=a[5] max=95 SWAP
i=6
A[6]>max 44>55 NO

15. • The Fibonacci Sequence is the series of numbers:
• 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...
...
• Fibonacci Series is a pattern of numbers where each number is
the result of addition of the previous two consecutive numbers .
• First 2 numbers start with 0 and 1.
• The third numbers in the sequence is 0+1=1. The 4th number is
the addition of 2nd and 3rd number i.e. 1+1=2 and so on.
The next number is found by adding up the two numbers before
it:
• the 2 is found by adding the two numbers before it (1+1),
• the 3 is found by adding the two numbers before it (1+2),
• the 5 is (2+3),
• and so on!

16. f1 f2 f3
f1 f2
f3
{
f3 = f1 + f2;
printf(" %d", f3);
f1 = f2;
f2 = f3;
}

18. How to reverse a number mathematically.
• Step 1 — Isolate the last digit(rem) in number.
rem = number % 10
The modulo operator (%) returns the remainder of a divison.
• Step 2 — Append lastDigit(rem) to reverse.
reverse = (reverse * 10) + rem
• Step 3-Remove last digit from number.
number = number / 10.