Availability
Generally speaking, higher-level programming languages are more likely to have garbage collection as a standard feature. In languages that do not have built in garbage collection, it can often be added through a library, as with the Boehm garbage collector for C and C++. This approach is not without drawbacks, such as changing object creation and destruction mechanisms.
Most functional programming languages, such as ML, Haskell, and APL, have garbage collection built in. Lisp, which introduced functional programming, is especially notable for introducing this mechanism.
Other dynamic languages, such as Ruby (but not Perl 5, or PHP, which use reference counting), also tend to use GC. Object-oriented programming languages such as Smalltalk, Java and ECMAScript usually provide integrated garbage collection. Notable exceptions are C++ and Delphi which have destructors. Objective-C has not traditionally had it, but ObjC 2.0 as implemented by Apple for Mac OS X uses a runtime collector developed in-house, while the GNUstep project uses a Boehm collector.
Historically, languages intended for beginners, such as BASIC and Logo, have often used garbage collection for heap-allocated variable-length data types, such as strings and lists, so as not to burden programmers with manual memory management. On early microcomputers, with their limited memory and slow processors, BASIC garbage collection could often cause apparently random, inexplicable pauses in the midst of program operation.
Some BASIC interpreters, such as Applesoft BASIC on the Apple II family, repeatedly scanned the string descriptors for the string having the highest address in order to compact it toward high memory, resulting in O(N*N) performance, which could introduce minutes-long pauses in the execution of string-intensive programs. A replacement garbage collector for Applesoft BASIC published in Call-A.P.P.L.E. (January 1981, pages 40–45, Randy Wigginton) identified a group of strings in every pass over the heap, which cut collection time dramatically. BASIC.System, released with ProDOS in 1983, provided a windowing garbage collector for BASIC that reduced most collections to a fraction of a second.
Read more about this topic: Garbage Collection (computer Science)
Famous quotes containing the word availability:
“Since ... six weeks ago, there has been no day in which I have not had letters and visits on the subject of my nomination for the Presidency.... I say very little. I have in no instance encouraged any one to work to that end.... I have said the whole talk about me is on the score of availability. Let availability do the work then.”
—Rutherford Birchard Hayes (1822–1893)