What are Arrays in C programming language

For understanding the arrays properly, let us consider the following program:

main( )

{ int x ; 

x = 5 ; 

x = 10 ; 

printf ( "\nx = %d", x ) ;

}

No doubt, this program will print the value of x as 10. Why so? Because when a value 10 is assigned to x, the earlier value of x, i.e. 5, is lost. Thus, ordinary variables (the ones which we have used so far) are capable of holding only one value at a time (as in the above example). However, there are situations in which we would want to store more than one value at a time in a single variable.

For example, suppose we wish to arrange the percentage marks obtained by 100 students in ascending order. In such a case we have two options to store these marks in memory:

(a) Construct 100 variables to store percentage marks obtained by 100 different students, i.e. each variable containing one student’s marks.
(b) Construct one variable (called array or subscripted variable) capable of storing or holding all the hundred values.
Obviously, the second alternative is better. A simple reason for this is, it would be much easier to handle one variable than handling 100 different variables. Moreover, there are certain logics that cannot be dealt with, without the use of an array. Now a formal definition of an array—An array is a collective name given to a group of ‘similar quantities’. These similar quantities could be percentage marks of 100 students, or salaries of 300 employees, or ages of 50 employees. What is important is that the quantities must be ‘similar’. Each member in the group is referred to by its position in the group. For example, assume the following group of numbers, which represent percentage marks obtained by five students.
per = { 48, 88, 34, 23, 96 }
If we want to refer to the second number of the group, the usual notation used is per2. Similarly, the fourth number of the group is referred as per4. However, in C, the fourth number is referred as per[3]. This is because in C the counting of elements begins with 0 and not with 1. Thus, in this example per[3] refers to 23 and per[4] refers to 96. In general, the notation would be per[i], where, i can take a value 0, 1, 2, 3, or 4, depending on the position of the element being referred. Here per is the subscripted variable (array), whereas i is its subscript.
Thus, an array is a collection of similar elements. These similar elements could be all ints, or all floats, or all chars, etc. Usually, the array of characters is called a ‘string’, whereas an array of ints or floats is called simply an array. Remember that all elements of any given array must be of the same type. i.e. we cannot have an array of 10 numbers, of which 5 are ints and 5 are floats.