Stack Pointer

Introduction

The Stack Pointer is a critical thing in pc structure, inside the realm of microprocessors and microcontrollers. It is a unique kind of pointer that constantly factors to the pinnacle of the stack. The stack is a linear information shape wherein insertion and deletion take place simplest at one cease. The stack follows a Last In First Out (LIFO) precept, which means the final entry you push onto the stack is the primary one you get again whilst you pop.

Role of the Stack Pointer

The Stack Pointer is a register that holds the address of the top of the stack. It is used for storing binary information during the execution of the program. When a new request arrives, it pushes down the previous requests. The Stack Pointer stores the address of the last program request. When inserting a program request to the stack, the Stack Pointer first increments by one. Then, the request is pushed to the stack.

Types of Stack

• Register Stack

The register stack is a memory device present in the memory unit, but it handles only a small amount of data. The stack depth is always limited in the register stack because the size of the register stack is very small compared to the memory. The push operation in the register stack involves incrementing the Stack Pointer by 1 and then entering the data into the stack. The pop operation involves reading data from the stack and then decrementing the Stack Pointer.

• Memory Stack

In the memory stack, the stack depth is flexible. It occupies a large amount of memory data, whereas in the register stack only a finite number of memory words will be stored. The push operation in the memory stack involves incrementing the Stack Pointer by 1 and then entering the data into the stack. The pop operation involves reading data from the stack and then decrementing the Stack Pointer.

The main difference between the two is the size limit (i.e., the number of elements they can hold). A Register Stack has a fixed size, while a Memory Stack can dynamically grow as needed.

Code:

Output:

Stack Overflow. Can't push to a full stack.
3
2
1
Stack Underflow. Can't pop from an empty stack.
None
b
a
Stack Underflow. Can't pop from an empty stack.
None

In the above code:

• Register Stack has a capacity attribute that limits the number of items it can hold. If you try to push an item when the stack is full, it will print "Stack Overflow. Can't push to a full stack."
• Memory Stack doesn't have a capacity attribute. It can hold an unlimited number of items (limited only by the available memory).
• Both classes have push and pop methods. The push method adds an item to the top of the stack, and the pop method removes an item from the top of the stack. If you try to pop an item when the stack is empty, it will print "Stack Underflow. Can't pop from an empty stack."

Operations on Stack

The two fundamental operations that could be carried out only in a particular stack are PUSH and POP.

Push Operation

The push operation is the process of adding an element to the stack. Here's how it works in both types of stacks:

• Register Stack
  1. The Stack Pointer increments by 1: SP←SP+1.
  2. Enter the data into the stack: M [SP]←DR, where DR is the Data Register.
  3. Check whether the stack is full or not. If the stack pointer equals 0 (sp=0), then the stack is full (full←1).
  4. Mark the stack as not empty: empty←0.
• Memory Stack
  1. The Stack Pointer increments by 1: SP←SP+1.
  2. Enter the data into the stack: M [SP]←DR.

Pop Operation

The pop operation is the process of removing an element from the stack. Here's how it works in both types of stacks:

• Register Stack
  1. Read data from the stack: DR←M [SP].
  2. Decrement the stack pointer: SP←SP-1.
  3. Check whether the stack is empty or not. If the stack pointer equals 0 (sp=0), then the stack is empty (empty←1).
• Memory Stack
  1. Read data from the stack: DR←M [SP].
  2. Decrement the stack pointer: SP←SP-1.

The applications of the stack pointer are

1. String Reversal: A stack can opposite a string through pushing characters onto the stack and then popping them back into the string in opposite order.
2. Balanced Parenthesis: A stack can take a look at if an expression has balanced parentheses with the aid of pushing each establishing parenthesis onto the stack and popping for every closing parenthesis.
3. UNDO/REDO: Stacks can implement UNDO and REDO operations in programs like textual content editors. Actions are driven onto the UNDO stack and popped onto the REDO stack while the UNDO operation is invoked.
4. System Stack for Activation Records: A stack is used to manipulate activation information during program execution. Each record carries statistics wanted for the execution of a process or function.
5. Infix, Prefix, Postfix Expressions: Stacks are used within the conversion and evaluation of infix, prefix, and postfix expressions.

Conclusion

In conclusion, the Stack Pointer plays a vital role in managing the stack in microprocessors. It helps in efficient memory utilization and simplifies the process of function calling and handling. Understanding the Stack Pointer and its operations is fundamental to understanding microprocessor operations and programming.