What distinguishes a stack from other data structures?

A stack is distinguished by its LIFO (Last In, First Out) principle of operation.

A stack is a linear data structure that follows a particular order in which operations are performed. The order is LIFO, which stands for Last In, First Out. This means that the last element added to the stack will be the first one to be removed. This is the key characteristic that distinguishes a stack from other data structures.

In a stack, all operations are performed at one end, known as the 'top' of the stack. This is unlike other data structures such as queues, where operations are performed at both ends, or arrays and linked lists, where operations can be performed at any position. The two main operations performed on a stack are 'push', which adds an element to the top of the stack, and 'pop', which removes the topmost element.

Another distinguishing feature of a stack is that it allows access to only the topmost element. This is in contrast to data structures like arrays or linked lists, where you can access any element directly. In a stack, if you want to access or remove an element that is not at the top, you would have to first remove all the elements above it. This is because a stack is designed to provide only the topmost element and the size of the stack to its outside world.

Stacks are used in many areas of computing. For example, they are used in algorithms to reverse a word, check balanced parentheses, evaluate postfix notation, etc. They are also used in system memory for function calls, in compiler operations, and for backtracking algorithms.

In summary, a stack is a unique data structure that operates on the LIFO principle, with all operations performed at the top of the stack, and only the topmost element and the size of the stack accessible to its outside world. These characteristics set it apart from other data structures.