Stacks and queues are fundamental linear data structures with distinct operational characteristics. Their applications are widespread in computer science, particularly in algorithms and system design. Understanding these applications is crucial for excelling in competitive exams like GATE.

Stacks operate on a Last-In, First-Out (LIFO) principle. This makes them ideal for tasks involving backtracking, undo mechanisms, and managing function calls.

When a function is called, its parameters, local variables, and return address are pushed onto a call stack. When the function returns, these are popped off. This mechanism ensures that functions are executed in the correct order and that control returns to the appropriate location.

Stacks are used to evaluate arithmetic expressions, particularly in converting infix notation (e.g., a + b) to postfix (e.g., ab+) or prefix (e.g., +ab). This conversion is essential for compilers and interpreters.

Problems like maze solving or N-Queens often involve exploring multiple paths. When a path leads to a dead end, backtracking allows us to return to a previous state. Stacks naturally support this by storing the sequence of choices made.

Many applications, like text editors, implement undo functionality using a stack. Each action is pushed onto an 'undo' stack. When undo is performed, the action is popped and reversed. A 'redo' stack can store these undone actions.

Queues operate on a First-In, First-Out (FIFO) principle, similar to a real-world queue. They are ideal for managing tasks that need to be processed in the order they arrive.

Operating systems use queues to manage processes waiting for CPU time. Processes are added to the ready queue and executed in the order they arrive (or based on scheduling algorithms). Similarly, I/O requests are often handled using queues.

BFS is a graph traversal algorithm that explores all the neighbor nodes at the present depth prior to moving on to the nodes at the next depth level. A queue is essential for keeping track of the nodes to visit next.

Queues are used as buffers in scenarios where data is produced at one rate and consumed at another. For example, in streaming media, a buffer queue ensures smooth playback by storing upcoming data.

Queues are vital in discrete event simulations, such as simulating customer queues at a bank or traffic flow. Events are often placed in a queue based on their scheduled time.

Focus on understanding the core LIFO and FIFO principles and how they map to specific algorithmic problems. Be prepared to trace the execution of algorithms involving stacks and queues, especially expression conversions and graph traversals like BFS.