Can you undo or redo any previous changes without changing the recent ones in text editors?
Likewise, the CPU also uses the stack for its operation, and its access method is called LIFO.
Users mailed me a lot to know about this stacking feature in the CPU.
So, lets begin without any delay!
What is a Stack in a CPU?
A stack is an abstract data variant that includes a collection of elements.
Specifically, it is a data storage structure that extracts the most, recently stored data.
The stack is a bunch of memory locations for the registers that store the top-of-element address for the computers.
By this, a stack is also called a memory containing an address register.
And those registers are called Stack Pointer or SP.
However, the top elements address in a stack is consistently affected by the SP.
The stack pointer can add or remove any element from the stack.
Thats why Push and Pop are the main two operations executed on the operators.
These two operations get executed from one end only.
Though they are quite different.
We all know what a spring-loaded tray dispenser is.
Therefore, you loaded the number 4 plate in the last and number 3 first.
So, here, plate number 4 is the Last In plate and also the First Out.
Thats how theLIFOor Stack feature works on any CPU.
Here, the stack pointer register holds the address of the top element of the stack.
Consider the following figures 64-word register, where the stack pointer register contains a binary number.
This binary number is the address of the stacks top element.
In this figure, A, B, and C these three elements located in the stack.
And the new word is pushed to that incremented location.
Similarly, when 000000 gets decremented by 1 the result becomes 111111.
However, if the stack is full, the one-bit register FULL will be set to 1.
Correspondingly, the one-bit registerEMTYwill be set to 1 if the stack is null.
The data register or DR holds the binary information which gets composed into or read out of the stack.
A new element will add to the stack through push operation since the stack is not full.
If (SP = 0) then (Full 1)// Checking whether the stack is full.
EMTY 0// Marking the stack is not empty.
Now, the memory write operation inserts the data registers word into the stack.
The stack will be full, and FULL will be set to 1 when the SP is at 0.
When the address of the element is at 0, there wont be any empty registers in the stack.
Thus, theEMTYwill be set to 0.
Below are the sequences of micro-operations, including pop operations:
SP SP 1//Decrementing the SP.
If (SP = 0) then (EMTY 1)//Checking whether the stack is empty.
FULL 0//Marking the stack is not full.
When SP reaches to 0, the stack becomes empty andEMTYget sets to 1.
Memory Stack
Another implementation of the stack is the memory stack.
A computers memory area is divided into three parts:program,data, andstack.
The pointer Program Counter (PC) stores the address of the next instruction in the program.
Plus, the Address Register (AR), indicates an array of information.
Meanwhile, the stack pointer controls the location of the top element of the stack.
So, the three registers that are related to the common bus arePC,AR, andSP.
From the figure above, the stack pointer (SP) indicates the starting value in2001.
Next, the stack gets increased by decreasing the addresses.
K SP [DR]
When it inserts another element, the SP is deducted by 1.
It can also identify the location of the next word.
TheMemory Write Operationthen inserts a word from the DR to the top of the stack.
However, it can also delete an element from the stack.
To do that, it applies the pop operation.
At this time, two CPU registers will check the stack limit.
With everything said, the stack-based operation is a way toexecute processes by the CPU.
Advantages & Disadvantages of Stack-based CPU Organizations
Stack-based CPU operations both have advantages and disadvantages.
Among the benefits, this stack operations can solve any complicated arithmetic expression with competent computation.
As for the disadvantages, the program size increases during the stack operations.
FAQs
What are the disadvantages of stack-based CPU operations?
The main demerit of the stack is the program size increases while using stack operations.
Plus, its slower because of using memory instead of registers for memory stack operations.
What are the main operations of the stack?
A stack mainly performs two types of operations, which arePush&Pop.
What is LIFO in a stack?
Final Words
Now, you know, CPUs use the stack to perform the operations.
In this article, I demonstrated what a stack is, and the way it operates.
Finally, you have a clear vision of stack-based operation in a CPU and how it works.
However, for more info, do let me know by leaving a comment in the box below.
See you again at the next one.
