In many computer programming languages == is a boolean logic binary relation representing equality. An example usage may be "x == y", which will return true if x is equal to y and false if it is not. Thus the below piece of code, using an if statement will print "x is equal to y" if x is equal to (holds the same value as) y and will print "x is not equal to y" if x is not equal to y. Computer code (HTML with JavaScript) in a tool that uses syntax highlighting (colors) to help the developer see the purpose of each piece of code. ... Boolean logic is a system of syllogistic logic invented by 19th-century British mathematician George Boole, which attempts to incorporate the empty set, that is, a class of non-existent entities, such as round squares, without resorting to uncertain truth values. ... In mathematics, the concept of binary relation, sometimes called dyadic relation, is exemplified by such ideas as is greater than and is equal to in arithmetic, or is congruent to in geometry, or is an element of or is a subset of in set theory. ... In mathematics, two mathematical objects are considered equal if they are precisely the same in every way. ... A conditional statement, in computer science, is a vital part of a programming language. ...

 if (x == y) { printf("x is equal to y"); } else { printf("x is not equal to y"); } 

Thus the == operator is a seperate operator to the = operator in languages that use == to test for equality and = for assignment. Languages that use this style include all C style languages, such as C and Java. In most imperative computer programming languages, the assignment operation is one of the basic operations. ... The C Programming Language, Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a general-purpose, procedural, imperative computer programming language developed in the early 1970s by Dennis Ritchie for use on the UNIX... Java is an object-oriented programming language developed by James Gosling and colleagues at Sun Microsystems in the early 1990s. ...

The similarity in appearance between "==" and "=" in these languages can lead to a particularly nasty kind of bug. A programmar may type "if (x = y)" when they intended to type "if (x == y)". The former code fragment roughly means "assign x to y, and if that succeeds (successful operations return true), execute the statement following". This will typically always execute the following statement, because the assignment operation will always succeed. The latter code fragment roughly means "if and only if x is equal to y, execute the code below". For example, the following code should print "x is 2 and y is 2" because "if (x = y)" assigns x to y, making both equal to 2, and then following the successful assignment executes the following code. A computer bug is an error, flaw, mistake, failure, or fault in a computer program that prevents it from working correctly or produces an incorrect result. ...

 int x = 1; int y = 2; if (x = y) { /* This code will always execute */ printf("x is %d and y is %d", x, y); } 

In most cases where a programmar mistypes "==" and accidentally writes something of the form "if (x = y)" they have created a bug. Firstly, they have assigned one value to another when that was certainly not their intention - if a programmer is attempting to test the equality of two variables then it is likely that there are situations in which they are not intended to be equal. Secondly, the code following the if statement will execute even in situations where it is not intended to, leading to many further bugs. Since at first glance it is difficult to distinguish between "=" and "==", this type of bug can be hard to spot.

For this reason, many non-C style languages, such as Eiffel, Pascal and Ada use "=" for equality testing and ":=" for assignment. These two syntactual elements are more easily distinguishable, and thus it is easier to spot situations where an assignment has been used mistakenly in place of an equality check. It is also harder to mistype an "=" as a ":=". Other languages, including Ada, forbid the use of assignment inside if statements. Some compilers, such as gcc, warn a user when they are compiling code that contains an assignment operator inside an if statement - gcc will print "warning: suggest parentheses around assignment used as truth value" when compiling code of the above form (but only when the "-Wall" or warn on all condition is set). Eiffel is an object-oriented programming language which emphasizes the production of robust software. ... Pascal is an imperative computer programming language, developed in 1970 by Niklaus Wirth as a language particularly suitable for structured programming. ... Ada is a structured, statically typed imperative computer programming language designed by a team led by Jean Ichbiah of CII Honeywell Bull during 1977–1983. ... Ada is a structured, statically typed imperative computer programming language designed by a team led by Jean Ichbiah of CII Honeywell Bull during 1977–1983. ... The GNU Compiler Collection (usually shortened to GCC) is a set of programming language compilers produced by the GNU Project. ...

It is typical on some technology oriented websites such as Slashdot to see users using a variety of slang which is a mixture of programming code and their native spoken and written language, such as english. This slang may include it's writer substituting "==" for the "=" sign used normally in mathematics or abbreviating "equals" in text to "==". By the mid 20th century humans had achieved a level of technological mastery sufficient to leave the surface of the planet for the first time and explore space. ... The front page of the English Wikipedia Website. ... Slashdot (often abbreviated to /.) is a popular technology-related website/Forum updated many times daily with articles that are short summaries of stories on other websites with links to the stories and provisions for readers to comment on each story. ... Slang is the non-standard or non-dialectal use of words in a language of a particular social group, and sometimes the creation of new words or importation of words from another language. ...