Syntax of Array Declaration
data_type array_name [size];
or
data_type array_name [size1] [size2]...[sizeN];C Array Initialization
Initialization in C is the process to assign some initial value to the variable. When the array is declared or allocated memory, the elements of the array contain some garbage value. So, we need to initialize the array to some meaningful value. There are multiple ways in which we can initialize an array in C.
1. Array Initialization with Declaration
In this method, we initialize the array along with its declaration. We use an initializer list to initialize multiple elements of the array. An initializer list is the list of values enclosed within braces { } separated b a comma.
data_type array_name [size] = {value1, value2, ... valueN};2. Array Initialization with Declaration without Size
If we initialize an array using an initializer list, we can skip declaring the size of the array as the compiler can automatically deduce the size of the array in these cases. The size of the array in these cases is equal to the number of elements present in the initializer list as the compiler can automatically deduce the size of the array.
data_type array_name[] = {1,2,3,4,5};The size of the above arrays is 5 which is automatically deduced by the compiler.
3. Array Initialization after Declaration (Using Loops)
We initialize the array after the declaration by assigning the initial value to each element individually. We can use for loop, while loop, or do-while loop to assign the value to each element of the array.
for (int i = 0; i < N; i++) {
array_name[i] = valuei;
}Access Array Elements
We can access any element of an array in C using the array subscript operator [ ] and the index value i of the element.
array_name [index];One thing to note is that the indexing in the array always starts with 0, i.e., the first element is at index 0 and the last element is at N – 1 where N is the number of elements in the array.
Update Array Element
We can update the value of an element at the given index i in a similar way to accessing an element by using the array subscript operator [ ] and assignment operator =.
array_name[i] = new_value;C Array Traversal
Traversal is the process in which we visit every element of the data structure. For C array traversal, we use loops to iterate through each element of the array.
Array Traversal using for Loop
for (int i = 0; i < N; i++) {
array_name[i];
}Types of Array in C
There are two types of arrays based on the number of dimensions it has. They are as follows:
- One Dimensional Arrays (1D Array)
- Multidimensional Arrays
1. One Dimensional Array in C
The One-dimensional arrays, also known as 1-D arrays in C are those arrays that have only one dimension.
Syntax of 1D Array in C
array_name [size];2. Multidimensional Array in C
Multi-dimensional Arrays in C are those arrays that have more than one dimension. Some of the popular multidimensional arrays are 2D arrays and 3D arrays. We can declare arrays with more dimensions than 3d arrays but they are avoided as they get very complex and occupy a large amount of space.
Syntax of 2D Array in C
array_name[size1] [size2];Properties of Arrays in C
It is very important to understand the properties of the C array so that we can avoid bugs while using it. The following are the main properties of an array in C.
1. Fixed Size
The array in C is a fixed-size collection of elements. The size of the array must be known at the compile time and it cannot be changed once it is declared.
2. Homogeneous Collection
We can only store one type of element in an array. There is no restriction on the number of elements but the type of all of these elements must be the same.
3. Indexing in Array
The array index always starts with 0 in C language. It means that the index of the first element of the array will be 0 and the last element will be N – 1.
4. Dimensions of an Array
A dimension of an array is the number of indexes required to refer to an element in the array. It is the number of directions in which you can grow the array size.
5. Contiguous Storage
All the elements in the array are stored continuously one after another in the memory. It is one of the defining properties of the array in C which is also the reason why random access is possible in the array.
6. Random Access
The array in C provides random access to its element i.e we can get to a random element at any index of the array in constant time complexity just by using its index number.
7. No Index Out of Bounds Checking
There is no index out-of-bounds checking in C/C++, for example, the following program compiles fine but may produce unexpected output when run.
