Syntax error

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For 2003 film, see Syntax Error (film).

In computer science, a syntax error is an error in the syntax of a sequence of characters or tokens that is intended to be written in a particular programming language.

For compiled languages syntax errors occur strictly at compile-time. A program will not compile until all syntax errors are corrected. For interpreted languages, however, not all syntax errors can be reliably detected until run-time, and it is not necessarily simple to differentiate a syntax error from a semantic error; many don't try at all.

In 8-bit home computers that used BASIC interpreter as their primary user interface, the SYNTAX ERROR error message became somewhat notorious, as this was the response to any command or user input the interpreter couldn't parse.

A syntax error may also occur when an invalid equation is entered into a calculator. This can be caused, for instance, by opening brackets without closing them, or less commonly, entering several decimal points in one number.

In Java the following is a syntactically correct statement:

System.out.println("Hello World");

while the following is not:

System.out.println(Hello World);

The second example would theoretically print the variable Hello World instead of the words Hello World. However, a variable in Java cannot have a space in between, so the syntactically correct line would be System.out.println(Hello_World).

A compiler will flag a syntax error when given source code that does not meet the requirements of the language grammar.