On 8-bit processors it is 16 bit, but in some processors (MosTek 65xx) the upper eight bit is constant 00000001.
Stack pointer points to the topmost / most recently referenced location on the stack; - Nutan
top pointer of a stack is the pointer that refers to the top most element of the stack.
In the 8051 microcontroller, the maximum address in the stack is typically 0x07FF, which is the highest addressable location in the internal RAM. However, since the stack grows downwards from the top of the internal RAM, the stack pointer (SP) typically starts at 0x07 and can go down to 0x00. Thus, the effective stack limit is determined by the available internal RAM and the starting point of the stack pointer, which can be set to a maximum of 0x07 in the standard configuration.
A stack is a data structure in which last item inserted is taken out first . That's why they are known as LIFO (last in first out). Inserting an item in stack is termed as push and taking an item out from stack I s termed as pop. Stack pointer is the pointer that points to the top of the stack or that points the item at the top of the stack and help in adding or deleting the item from the top of stack.
Actually, stack data starts one location greater than the stack pointer. In the Intel design, the stack pointer always points to the next location to be used on a push, and pushes always decrement the pointer. It is more correct to say that the stack region to be used next is one location less than the stack pointer's register address.
Accessing a stack.
Its not a stack counter - its a stack pointer. The stack pointer is a register that points to the top of the stack. In the Intel configuration, it points to the next item to be popped off the stack. To push an item requires that the stack pointer be decremented first, and then the item is written. The inverse operation - the pop - requires read then increment.
Because the stack pointer marks the top of the stack. If it is not initialised, it is not possible to determine where the next stack frame will go.
A stack is a data structure in which last item inserted is taken out first . That's why they are known as LIFO (last in first out). Inserting an item in stack is termed as push and taking an item out from stack I s termed as pop. Stack pointer is the pointer that points to the top of the stack or that points the item at the top of the stack and help in adding or deleting the item from the top of stack.
If your stack grows bottom-up, it's decremented when you leave a function; if the stack grows top-down, the stack pointer is incremented.
If the stack is empty assume the stack pointer has a value of P. when you push something on the stack you increment P. when you pull something from stack you decrement P.
A stack pointer is a register pointing to the top of a stack. It supports the fundamental stack manipulations (push and pop) in an efficient manner. Most micro processor hardware has build-in hardware support for stack pointers, typically both in form of dedicated stack pointer registers and in form of addressing modes which support the creation and maintenance of stacks through general-purpose pointer registers. In software, many programming languages feature constructs suited for implementation of stack pointers within the high-level language (such as post-increment and pre-decrement operators in C).