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The void type, in several programming languages derived from C and Algol68, is the return type of a function that returns normally, but does not provide a result value to its caller. Usually such functions are called for their side effects , such as performing some task or writing to their output parameters.
If a function has the return type void, the return statement can be used without a value, in which case the program just breaks out of the current function and returns to the calling one. [1] [2] Similar syntax is used in other languages including Modula-2 [3] and Python. [4] In Pascal there is no return statement. Functions or procedures ...
the return type is int.The program can therefore rely on the method returning a value of type int.Various mechanisms are used for the case where a subroutine does not return any value, e.g., a return type of void is used in some programming languages:
In some of these languages an extra keyword is used to declare no return value; for example void in C, C++ and C#. In some languages, such as Python, the difference is whether the body contains a return statement with a value, and a particular callable may return with or without a value based on control flow.
In C, C++, C#, D, and PHP, void is used to designate a function that does not return anything useful, or a function that accepts no arguments. The unit type in C is conceptually similar to an empty struct, but a struct without members is not allowed in the C language specification (this is allowed in C++).
POD return values 33–64 bits in size are returned via the EAX:EDX registers. Non-POD return values or values larger than 64-bits, the calling code will allocate space and passes a pointer to this space via a hidden parameter on the stack. The called function writes the return value to this address. Stack aligned on 4-byte boundary. stdcall ...
I/O is inherently impure: input operations undermine referential transparency, and output operations create side effects.Nevertheless, there is a sense in which a function can perform input or output and still be pure, if the sequence of operations on the relevant I/O devices is modeled explicitly as both an argument and a result, and I/O operations are taken to fail when the input sequence ...
A callback is often back on the level of the original caller. In computer programming, a callback is a function that is stored as data (a reference) and designed to be called by another function – often back to the original abstraction layer.