What is Stack in Data Structure?

In C language, a stack is an abstract data type that represents a collection of elements with two main operations: push and pop. It follows the Last In First Out (LIFO) principle, which means that the element added last to the stack will be the first one to be removed.

The stack can be implemented in C language using various data structures such as arrays, linked lists, and dynamic arrays. The most common implementation is using an array because it is simple and efficient.

In a stack implemented using an array, the top of the stack is represented by an index variable that points to the last element inserted in the stack. When an element is pushed into the stack, the top index is incremented, and when an element is popped, the top index is decremented.

Here is an example of defining a stack using an array in C language:

#define MAX_SIZE 100

int stack[MAX_SIZE];
int top = -1;

In this example, we defined a stack of a maximum size of 100, which is represented by the stack array. The top variable is initially set to -1, indicating that the stack is empty.

To perform stack operations, such as push and pop, we can use functions that manipulate the stack elements and the top index.