The void type, in several programming languages derived from C and Algol68, is the type for the result 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. The usage of the void type in such context is comparable to that of the syntactic constructs which define subroutines in Visual Basic and procedures in Pascal. It is also similar to the unit type used in functional programming languages and type theory; however, there are some differences in allowable usage, in that the void type is taken to be an empty type with no values. See Unit type#In programming languages for a comparison.
C and C++ also support the pointer to void type (specified as void *), but this is an unrelated notion. Variables of this type are pointers to data of an unspecified type, so in this context (but not the others) void acts as a universal or top type. A program can convert a pointer to any type of data (except a function pointer) to a pointer to void and back to the original type without losing information, which makes these pointers useful for polymorphic functions.
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Famous quotes containing the words void and/or type:
“Your children are not here to fill the void left by marital dissatisfaction and disengagement. They are not to be utilized as a substitute for adult-adult intimacy. They are not in this world in order to satisfy a wife’s or a husband’s need for love, closeness or a sense of worth. A child’s task is to fully develop his/her emerging self. When we place our children in the position of satisfying our needs, we rob them of their childhood.”
—Aaron Hess (20th century)
“The more characteristic American hero in the earlier day, and the more beloved type at all times, was not the hustler but the whittler.”
—Mark Sullivan (1874–1952)