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A pop or pull operation: a data item at the current location to which the stack pointer points is read, and the stack pointer is moved by a distance corresponding to the size of that data item. There are many variations on the basic principle of stack operations. Every stack has a fixed location in memory at which it begins.
The stack is often used to store variables of fixed length local to the currently active functions. Programmers may further choose to explicitly use the stack to store local data of variable length. If a region of memory lies on the thread's stack, that memory is said to have been allocated on the stack, i.e. stack-based memory allocation (SBMA).
Such a variable can be address without an explicit pointer reference (xxx=1;, or may be addressed with an explicit reference to the default locator (ppp), or to any other pointer (qqq->xxx=1;). Pointer arithmetic is not part of the PL/I standard, but many compilers allow expressions of the form ptr = ptr±expression.
This uses operations to copy stack entries. The stack must be depth shallow enough for the CPU's available copy instructions. Hand-written stack code often uses this approach, and achieves speeds like general-purpose register machines. [30] [9] Unfortunately, algorithms for optimal "stack scheduling" are not in wide use by programming languages.
In computer science, an in-tree or parent pointer tree is an N-ary tree data structure in which each node has a pointer to its parent node, but no pointers to child nodes. When used to implement a set of stacks , the structure is called a spaghetti stack , cactus stack or saguaro stack (after the saguaro , a kind of cactus). [ 1 ]
The outer variable "owns" the reference. In the programming language C++, this technique is readily implemented and demonstrated with the use of const references. Reference counting in C++ is usually implemented using "smart pointers" [18] whose constructors, destructors, and assignment operators manage the references. A smart pointer can be ...
The C programming language manages memory statically, automatically, or dynamically.Static-duration variables are allocated in main memory, usually along with the executable code of the program, and persist for the lifetime of the program; automatic-duration variables are allocated on the stack and come and go as functions are called and return.
Pointer formats are known as near, far, or huge. Near pointers are 16-bit offsets within the reference segment, i.e. DS for data and CS for code. They are the fastest pointers, but are limited to point to 64 KB of memory (to the associated segment of the data type). Near pointers can be held in registers (typically SI and DI).