Arrays

An array is a collection of data items of the same type
Items are stored at contigous memory locations (items are placed right next to each other)
It can also store the collection of derived data types, such as pointers, structures, etc
The C language places no limits on the number of dimensions in an array.

Most Commonly used dimensions of Array :

A one-dimensional array is like a list.
A two-dimensional array is like a table.

Some texts refer to one-dimensional arrays as vectors, two-dimensional arrays as mactires, and use the general term arrays when the number of dimensions is unspecified or unimportant.

Why do we need arrays?

Code that use arrays is sometimes more organized and readable.
Arrays allow us to create many variables by just a single line. It means there is no need to create or specify each and every variable.
If you were to store the marks in a test of 56 students, creating 56 variable will make program look cluttered and messy.
Solution to this is arrays!
We can create arrays of integers and store the consecutive marks corresponding to the roll number in the array.

Advantages of arrays

It is used to represent multiple data items of same type by using only single name.
Accessing an item in a given array is very fast!
2 Dimensional arrays makes it easy in mathematical applications as it is used to represent a matrix.

Properties of array

Data in an array is stored in contiguous memory locations in RAM
Each element of an array is of same size
Any element of the array with given index can be accessed very quickly by using its address which can be calculated using the base address and the index.
Index No. - It is the special type of no. which allows us to access variables of Arrays i.e. index no. provides a method to access each element of an array in a program.

Syntax for declaring and initializing an array

data_type name[size];
data_type name[size] = {x,y,z,.....}; //size not required in this case!
data_type name[rows][columns]; //for 2-d arrays
we can also initialize the array one by one by accessing it using its index:
- name[0]=0;

                            

                                    #include <stdio.h>

                                    int main()
                                    {
                                        int marks[4];
                                        int marks2[]={2,3,55,33,553}; //declaration with initialization
                                        // marks[0]=34;
                                        // printf("Marks of student 1 is %d\n", marks[0]);
                                        // marks[0]=454;
                                        // printf("Marks of student 1 is %d\n", marks[0]);
                                        // for (int i = 0; i < 4; i++)
                                        // {
                                        // printf("Enter the value of %d element of the array\n", i);
                                        // scanf("%d",&marks[i]);
                                        // }
                                        // for (int i = 0; i < 4; i++)
                                        // {
                                        // printf("The value of %d element of the array is %d\n",i, marks[i]);
                                    
                                        // }
                                    
                                        //2d array
                                       int student[][4]={{1,2,3,4},{3,4,5,6}}; //here we have to declare atleast with column numbers
                                       //printing the array
                                    
                                       for ( int i = 0; i < 2; i++) //double for loop in 2d array
                                        {
                                       for (int j = 0; j < 4; j++)
                                        {
                                        printf("Value of %d, %d element of the array is %d\n",i,j,student[i][j]);
                                        }
                                    
                                        }
                                       return 0;
                                    }

Disadvantages of using arrays

Poor time complexity of insertion and deletion operation
Wastage of memory since arrays are fixed in size.
If there is enough space present in the memory but not in contiguous form, you will not be able initialize your array.
It is not possible to increase the size of the array, once you have declared the array.

C Programming

Arrays

Most Commonly used dimensions of Array :

Why do we need arrays?

Advantages of arrays

Properties of array

Syntax for declaring and initializing an array

Disadvantages of using arrays