Stack Operations
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The document discusses stack data structures and their implementation in CPU organization. It describes stacks as last-in, first-out (LIFO) data structures that support two main operations: push and pop. It then covers register and memory-based stack implementations, including the use of stack pointers, data registers, and algorithms for push and pop in each case. The key difference is that register stacks grow with increasing addresses while memory stacks grow with decreasing addresses. The document concludes with an example of how stacks are used to evaluate arithmetic expressions by operating on the top two elements of the stack.
Stack Operations
- 1. 1MADE BY RIDA ZAMAN
- 2. STACK Stack is a data structure in which last item inserted is taken out first It works in LIFO manner (last in first out) 2MADE BY RIDA ZAMAN
- 3. OPERATIONS ON STACK We can perform two operation on a stack INSERTION (PUSH) DELETION (POP) 3MADE BY RIDA ZAMAN
- 4. STACK ORGANIZATION IN STACK ORGANIZATION WE STORE OR PLACE OUR DATA IN A MANNER OF A STACK. 4MADE BY RIDA ZAMAN
- 5. STACK POINTER It’s an register which is used to store the address of the top item in the stack It’s a 6-bit register 5MADE BY RIDA ZAMAN
- 6. DATA REGISTER Whatever value we INSERT(PUSH) or DELETE(POP) from the stack it stores in data register It’s a 2byte register /16bits 6MADE BY RIDA ZAMAN
- 7. TYPES OF STACK ORGANIZATION There are two types of stack organization we have for our CPU REGISTER STACK MEMORY STACK 7MADE BY RIDA ZAMAN
- 8. REGISTER STACK If we have for example finite number of words which we want to insert at top of another and making stack out of it through register stack. 8MADE BY RIDA ZAMAN
- 9. SINGLE BIT REGISTER We have two single bit registers FULL: If the entire stack is full then this full register will set to be 1 EMPTY: If the entire stack is empty then this empty register will set to be 1 9MADE BY RIDA ZAMAN
- 10. ALGORITHM FOR PUSH SPSP+1 M{SP}DR IF(SP=0)THEN (F1) EMPTY0 10MADE BY RIDA ZAMAN
- 11. ALGORITHM FOR PUSH STEP BY STEP SPSP+1 Increment stack by a value 1 M{SP}DR Whatever content present in data register place it inside the memory word to which stack pointer is presently pointing IF(SP=0)THEN (F1) We are performing push operation so we may encounter a position where our stack would become full so we have to set our full bit to 1 If our stack pointer is equal to zero set full=1 EMPTY0 Because we are putting values into the stack so its not empty anymore 11MADE BY RIDA ZAMAN
- 12. ALGORITHM FOR POP DRM{SP} SPSP-1 IF {SP=0}{EMPTY1} FULL0 12MADE BY RIDA ZAMAN
- 13. ALGORITHM FOR POP STEP BY STEP DRM{SP}Whatever content I have in the memory word that the stack pointer is pointing at present store it in the data register SPSP-1 The stack pointer should point to the next top element ,it must be decremented by a value-1 IF{SP=0}{EMPTY1} We are performing POP operation so we may encounter a position where our stack would become entirely empty at that point we will set empty =1 FULL0 Because we are deleting values from stack so its obvious that it wont become full at any point 13MADE BY RIDA ZAMAN
- 14. MEMORY STACK In Memory stack we have a Memory Unit In memory unit we divide memory into 3 portions PROGRAM(INSTRUSTIONS): it is use to access/fetch instructions from memory DATA(OPERANDS): it is use to access/fetch data and operands from memory STACK: it is use to push or pop item into the stack In memory stack our stack grows with decreasing address There is different algorithm for both memory and register stacks 14MADE BY RIDA ZAMAN
- 15. MEMORY UNIT 15MADE BY RIDA ZAMAN
- 17. ALGORITHM FOR PUSH STEP BY STEP SPSP-1 The first operation we will do is we will decrement our stack pointer M{SP}DR Whatever data we have in the data register we should place it at the memory word at which the stack pointer is pointing at 17MADE BY RIDA ZAMAN
- 18. ALGORITHM FOR POP STEP BY STEP DRM{SP} Whatever content I have in the memory word of stack pointer I have to place it into data register SPSP+1 Then we’ll increment our stack pointer by 1 18MADE BY RIDA ZAMAN
- 19. DIFFERENCE BETWEEN REGISTER STACK AND MEMORY STACK The stack grows with increasing address in register stack Register stack is generally on the CPU Access to register stack is fast Register stack is limited size wise The stack grows with decreasing address in register stack Memory stack is on the RAM(main memory) Access to memory stack is not as fast as register stack Memory stack is larger then register stack size wise 19MADE BY RIDA ZAMAN
- 20. PRACTICAL APPLICATION OF HOW STACK ORGANIZATION WORKS INSIDE OUR CENTRAL PROCESSING UNIT 20MADE BY RIDA ZAMAN
- 21. DIFFERENT NOTATIONS WE HAVE IN REPRESENTING ARITHMETIC NOTATIONS INFIX PREFIX (POLISH NOTATION) POSTFIX (REVERSE POLISH NOTATION/RPN) 21MADE BY RIDA ZAMAN
- 22. INFIX NOTATION In INFIX notation we have to write the operator in between the operands 22MADE BY RIDA ZAMAN
- 23. PREFIX NOTATION In PREFIX notation we have to write the operator before the operands Most of the computer use PREFIX notation to execute arithmetic operations 23MADE BY RIDA ZAMAN
- 24. POSTFIX (REVERSE POLISH NOTATION/RPN) In POSTFIX notation we have to write the operator after the operands 24MADE BY RIDA ZAMAN
- 25. EXAMPLE: 25MADE BY RIDA ZAMAN
- 26. SO WHAT THE COMPUTER DOES? It scan the particular expression from left to right whenever it encounters an operator it does the particular operation on the previous two elements/operands that are scanning 26MADE BY RIDA ZAMAN
- 27. HOW STACK ORGANIZATION IS USE TO EVALUATE ARITHEMATIC EXPRESSIONS 27MADE BY RIDA ZAMAN
- 28. WHEN AN OPERATOR IS ENCOUNTERED The two top most elements in the stack are use for the operation The stack is popped and the result of the operation replaces the lower operand 28MADE BY RIDA ZAMAN
- 29. EXAMPLE: 29MADE BY RIDA ZAMAN
- 30. 30MADE BY RIDA ZAMAN