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GOTO is a statement found in many computer programming languages. It is a combination of the English words go and to. When executed it causes an unconditional transfer of control (a "jump") to another statement. The jumped-to statement is specified using some kind of label, which may be an identifier or a line number depending on the language. At the machine code level a goto is a form of branch or jump statement. A statement is the minimal unit of structuring in imperative programming languages. ...
A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. ...
In computer science control flow (or alternatively, flow of control) refers to the order in which the individual statements or instructions of an imperative program are performed or executed. ...
A label is any kind of tag attached with adhesive to something so as to identify the object or its contents. ...
Identifiers (IDs) are lexical tokens that name entities. ...
In computing, a line number is a way of specifying a point in a file by enumerating each line in the file by a number. ...
Machine code or machine language is a system of instructions and data directly understandable by a computers central processing unit. ...
A branch (or jump on some computer architectures, such as the PDP-8 and Intel x86) is a point in a computer program where the flow of control is altered. ...
In some languages, goto functionality may be present without explicit use of the keyword goto, such as where a break or continue keyword may be followed by with an identifier denoting a label. The SNOBOL programming language supports a form of statement suffix which causes an unconditional transfer of control after the statement has finished executing. In computer programming, a keyword is a word or identifier that has a particular meaning to the programming language. ...
SNOBOL (StriNg Oriented symBOlic Language) is a computer programming language that was developed between 1962 and 1967 at AT&T Bell Laboratories by David J. Farber, Ralph E. Griswold and Ivan P. Polonsky. ...
GOTO statements are found in most high-level languages. There are a few high-level languages that do not support a goto statement, Java (where goto is a reserved word but does not presently serve any function), Python, Ruby, and PHP being the most well known. A high-level programming language is a programming language that is more user-friendly, to some extent platform-independent, and abstract from low-level computer processor operations such as memory accesses. ...
Java is a programming language originally developed by Sun Microsystems and released in 1995. ...
A reserved word is a word which, in some computer programming language, cannot be used as an identifier because it is already used for some grammatical purpose. ...
Python is an interpreted programming language created by Guido van Rossum in 1990. ...
Ruby is a reflective, object-oriented programming language. ...
PHP is a reflective programming language originally designed for producing dynamic web pages. ...
Usage
The goto statement is often combined with the if statement to cause a conditional transfer of control. “Then†redirects here. ...
IF condition THEN goto label; Some languages are case sensitive and require keywords to be written either in upper or lower case. In languages that are not case sensitive the choice is left to the author of the code. Text sometimes exhibits case sensitivity, that is, words can differ in meaning based on the differing use of uppercase and lowercase letters. ...
In computer science, a keyword is an identifier which indicates a specific command. ...
Criticism of goto usage The GOTO statement has been the target of much criticism, the claim being that use of GOTO produces unreadable and generally unmaintainable "spaghetti code". As structured programming became more popular in the 1960s and 1970s, many computer scientists came to the conclusion that programs should always use so-called 'structured' flow-control commands such as loops and if-then-else statements in place of GOTO. However, others believed that use of GOTO did not unconditionally lead to poor quality code and that there are some tasks that cannot be straightforwardly accomplished in many programming languages without the use of one or more GOTO statements, such as implementing finite state machines, breaking out of nested loops and exception handling. Spaghetti code is a pejorative term for source code which has a complex and tangled control structure, especially one using many GOTOs, exceptions, threads, or other unstructured branching constructs. ...
Structured programming can be seen as a subset or subdiscipline of procedural programming, one of the major programming paradigms. ...
The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ...
The 1970s decade refers to the years from 1970 to 1979, also called The Seventies. ...
Computer science (informally: CS or compsci) is, in its most general sense, the study of computation and information processing, both in hardware and in software. ...
In computer science and in computer programming, statements in pseudocode or in a program are normally obeyed one after the other in the order in which they are written (sequential flow of control). ...
Fig. ...
Exception handling is a programming language construct or computer hardware mechanism designed to handle the occurrence of some condition that changes the normal flow of execution. ...
Probably the most famous criticism of GOTO is a 1968 letter by Edsger Dijkstra called Go To Statement Considered Harmful [1]. In that letter Dijkstra argued that unrestricted GOTO statements should be abolished from higher-level languages because they complicated the task of analyzing and verifying the correctness of programs (particularly those involving loops). An alternative viewpoint is presented in Donald Knuth's Structured Programming with go to Statements [2] which analyzes many common programming tasks and finds that in some of them GOTO is the optimal language construct to use. Edsger Dijkstra Edsger Wybe Dijkstra (Rotterdam, May 11, 1930 – Nuenen, August 6, 2002; IPA: ) was a Dutch computer scientist. ...
In computer science and related disciplines, considered harmful is a phrase popularly used in the titles of diatribes and other critical essays. ...
Donald Ervin Knuth ( or Ka-NOOTH[1], Chinese: [2]) (b. ...
The Ada language design took note of the above criticisms, but the statement was included in the language despite them, mainly to support automatically generated code where the goto might prove indispensable.[citation needed] However, the labels used as the destination of a goto statement take the unusual form of an identifier enclosed in double angle brackets (e.g. <<Start_Again>>) and this syntax is not used anywhere else in the language. This makes it easy to check a program for the existence of goto destinations. The goto statement itself takes the simple form goto Start_Again;. Ada is a structured, statically typed imperative computer programming language designed by a team led by Jean Ichbiah of CII Honeywell Bull under contract to the United States Department of Defense during 1977–1983. ...
Variations There are a number of different language constructs which can be described as forms of goto:
Restricted GOTOs Many languages, such as C and Java, provide related control flow statements, like break and continue, which are effectively restricted forms of the goto statement. Their effect is an unconditional jump, but they can only be used to jump to a point after the end of a loop block - either to continue a loop at the next iteration (continue), or to end the loop (break). C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...
Java is a programming language originally developed by Sun Microsystems and released in 1995. ...
The word iteration is sometimes used in everyday English with a meaning virtually identical to repetition. ...
switch/case structures The switch statement in C, C++ and Java effectively performs a multi-way goto where the destination is selected by the value of an expression. In some other languages the switch (or case) statement does not behave in precisely this way (it does not have "fall-through" behaviourdfsdf). In computer programming, a switch statement is a type of control statement that exists in most modern imperative programming languages (e. ...
C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...
For a WikiBook on programming with C++, see Wikibooks: C++ Programming. ...
Java is a programming language originally developed by Sun Microsystems and released in 1995. ...
Computed GOTO A computed GOTO (originally Fortran terminology) either jumps to one of several labels based on the value of an expression, or jumps to a label that has been stored in a variable. The ON GOTO statement in BASIC supports the first kind of computed GOTO and is useful for case-by-case branching, as in C's switch statement. Some C compilers (e.g., gcc) support "goto" with a label variable using the label value operator. The label value operator && returns the address of its operand, which must be a label defined in the current function or a containing function. The value is a constant of type void* and should be used only in a computed goto statement. The feature is an extension to C and C++, implemented to facilitate porting programs developed with GNU C.[1] Fortran (previously FORTRAN[1]) is a general-purpose[2], procedural,[3] imperative programming language that is especially suited to numeric computation and scientific computing. ...
In computer programming, a switch statement is a type of control statement that exists in most modern imperative programming languages (e. ...
The GNU Compiler Collection (usually shortened to GCC) is a set of programming language compilers produced by the GNU Project. ...
Continuations A continuation is similar to a computed GOTO in that it transfers control from an arbitrary point in the program to a previously marked point. A continuation can be more flexible than GOTO in some languages because it can leave the current function, something that a GOTO cannot do in most languages. Executing a continuation usually involves some adjustment of the program's call stack in addition to a jump. The longjmp function of the C programming language is an example of an escape continuation that may be used to escape the current context to a surrounding one. The Common Lisp GO operator also has this stack unwinding property, despite the construct being lexically scoped, as the label to be jumped to can be referenced from a closure. In computing, a continuation is a representation of some of the execution state of a program (often the call stack and the current Instruction pointer) at a certain point. ...
In computer science, a call stack is a special stack which stores information about the active subroutines of a computer program. ...
The source is licensed under the GFDL, but has large invariant sections and cover texts. ...
C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...
Common Lisp, commonly abbreviated CL, is a dialect of the Lisp programming language, standardised by ANSI X3. ...
In computer programming, scope is an enclosing context where values and expressions are associated. ...
In programming languages, a closure is a function that refers to free variables in its lexical context. ...
"COME FROM" GOTO parody In the esoteric programming language INTERCAL, which is a parody of languages like BASIC, COME FROM is used instead of GOTO. An esoteric programming language (sometimes shortened to esolang[1]) is a programming language designed as a test of the boundaries of computer programming language design, as a proof of concept, or as a joke. ...
INTERCAL is a programming language parody, the canonical esoteric programming language. ...
In contemporary usage, a parody (or lampoon) is a work that imitates another work in order to ridicule, ironically comment on, or poke some affectionate fun at the work itself, the subject of the work, the author or fictional voice of the parody, or another subject. ...
In computer programming, Come from or COME FROM is a branching instruction or flow control instruction similar to Goto. Come from differs from Goto in the direction of the branching. ...
Perl GOTO In Perl, there is a variant of the goto statement that is not a traditional GOTO statement at all. It takes a function name and transfers control by effectively substituting one function call for another (a tail call): the new function will not return to the GOTO, but instead to the place from which the original function was called. Early versions of COBOL had the ALTER verb to accomplish this. Wikibooks has a book on the topic of Perl Programming Perl is a dynamic programming language created by Larry Wall and first released in 1987. ...
In computer science, tail recursion is a special case of recursion that can be transformed into an iteration. ...
This article does not cite any references or sources. ...
See also Unstructured programming is a programming paradigm where all code is contained in a single continuous block. ...
In computer science control flow (or alternatively, flow of control) refers to the order in which the individual statements or instructions of an imperative program are performed or executed. ...
References - ^ Dijkstra, Edsger: Go To Statement Considered Harmful. Communications of the ACM 11:3 (1968), 147–148.
- ^ Knuth, Donald: Structured Programming with Goto Statements. Computing Surveys 6:4 (1974), 261–301.
Edsger Dijkstra Edsger Wybe Dijkstra (Rotterdam, May 11, 1930 – Nuenen, August 6, 2002; IPA: ) was a Dutch computer scientist. ...
Donald Ervin Knuth ( or Ka-NOOTH[1], Chinese: [2]) (b. ...
External links - A Structured Discipline of Programming
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