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The name "peek" is similar to the basic "push" and "pop" operations on a stack, but the name for this operation varies depending on data type and language. Peek is generally considered an inessential operation, compared with the more basic operations of adding and removing data, and as such is not included in the basic definition of these data ...
Several of the C++ Standard Library container types have push_back and pop_back operations with LIFO semantics; additionally, the stack template class adapts existing containers to provide a restricted API with only push/pop operations. PHP has an SplStack class. Java's library contains a Stack class that is a specialization of Vector.
As most early home computers used 8-bit processors, PEEK or POKE values are between 0 and 255. Setting or reading a 16-bit value on such machines requires two commands, such as PEEK (A) + 256 * PEEK (A + 1) to read a 16-bit integer at address A, and POKE A, V followed by POKE A + 1, V / 256 to store a 16-bit integer V at address A.
With a stack stored completely in RAM, this does implicit writes and reads of the in-memory stack: Load X, push to memory; Load 1, push to memory; Pop 2 values from memory, add, and push result to memory; for a total of 5 data cache references. The next step up from this is a stack machine or interpreter with a single top-of-stack register.
After processing all the input, the stack contains 56, which is the answer.. From this, the following can be concluded: a stack-based programming language has only one way to handle data, by taking one piece of data from atop the stack, termed popping, and putting data back atop the stack, termed pushing.
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).
Input: 3 + 4 Push 3 to the output queue (whenever a number is read it is pushed to the output); Push + (or its ID) onto the operator stack; Push 4 to the output queue; After reading the expression, pop the operators off the stack and add them to the output.
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". Although maintenance of the call stack is important for the proper functioning of most software , the details are normally hidden and automatic in high-level programming languages .