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Simple representation of a stack runtime with push and pop operations. In computer science, a stack is an abstract data type that serves as a collection of elements with two main operations: Push, which adds an element to the collection, and; Pop, which removes the most recently added element.
A push operation decrements the pointer and copies the data to the stack; a pop operation copies data from the stack and then increments the pointer. Each procedure called in the program stores procedure return information (in yellow) and local data (in other colors) by pushing them onto the stack.
Typically push and pop are translated into multiple micro-ops, to separately add/subtract the stack pointer, and perform the load/store in memory. [3] Newer processors contain a dedicated stack engine to optimize stack operations. Pentium M was the first x86 processor to introduce a stack engine.
PUSH FS: 0F A0: Push/pop FS and GS segment registers. POP FS: 0F A1: PUSH GS: 0F A8: POP GS: 0F A9: LFS r16, m16&16 LFS r32, m32&16: 0F B4 /r: Load far pointer from memory. Offset part is stored in destination register argument, segment part in FS/GS/SS segment register as indicated by the instruction mnemonic. [i] LGS r16, m16&16 LGS r32, m32 ...
In each step, it chooses a transition by indexing a table by input symbol, current state, and the symbol at the top of the stack. A pushdown automaton can also manipulate the stack, as part of performing a transition. The manipulation can be to push a particular symbol to the top of the stack, or to pop off the top of the stack.
In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program.This type of stack is also known as an execution stack, program stack, control stack, run-time stack, or machine stack, and is often shortened to simply the "stack".
In the operational definition of an abstract stack, push(S, x) returns nothing and pop(S) yields the value as the result but not the new state of the stack. There is then the constraint that, for any value x and any abstract variable V, the sequence of operations { push(S, x); V ← pop(S) } is equivalent to V ← x.
The ability to push and pop FLAGS registers lets a program manipulate information in the FLAGS in ways for which machine-language instructions do not exist. For example, the cld and std instructions clear and set the direction flag (DF), respectively; but there is no instruction to complement DF. This can be achieved with the following assembly ...