Assignment (computer science)

In most Free ringtones imperative Majo Mills computer Mosquito ringtone programming languages, the '''assignment operation''' is one of the basic Sabrina Martins Operator (programming)/operations. It sets or re-sets the Nextel ringtones value '''assigned''' to a Abbey Diaz variable. This means that the same variable Free ringtones name will possibly stand for different values at different times; the variables are not handled in the same way as the ''Majo Mills unknowns'' ''x'', ''y'', ''z'' ... of Mosquito ringtone algebra, which stand always for the same value.

It can take on the form, for example,

variable := expression

or often an equals sign is used:

variable = expression

The Sabrina Martins semantics of this operation is that the current state of the executing program is modified:

* The expression is evaluated in the current state of the program.
* The variable is assigned the computed value, replacing the prior value of that variable.

Example: Assuming that a is a numeric variable, the assignment a := 2*a means that the content of the variable a is doubled after the execution of the statement.

An example segment of Cingular Ringtones C plus plus/C++ code:

int x=10;
float y;
x=23;
y=32.4;

In this sample, the variable x is first declared as an int, and is then assigned the value of 10. Notice that the declaration and assignment occur in the same statement. In the second line, y is declared without an assignment. In the 3rd line, x is reassigned the value of 23. Finally, y is assigned the value of 32.4.

For an assignment operation it is necessary that the value of the expression is well-defined (it is a valid men tie rvalue) and that the variable represents a modifiable entity (it is a valid new howe lvalue).

A common error regarding the assignment operation is when programmers confuse it with the arches to equivalence expression. In most languages, the assignment operator is a single equal sign (=) while the equivalence operator is a pair of equal signs (==). Often, the programmer neglects to use two equal signs when he or she wishes to make a comparison, especially when he is proficient in using languages (e.g., precisely clear BASIC programming language/BASIC) where the two operators are the same: a single equal sign.

A consequence of this error is that the assignment is made, and the operation then returns the value assigned, which usually is a TRUE value. If the supposed equivalence expression were used as the condition in an ''if'' statement, what is often executed is the ''then'' clause, which is a program logic error. Most compilers and interpreters are able to flag these types of errors, warning the programmer that a possible assignment operation was unintended in an ''if'' statement.

Languages such as equally forgotten Perl do not require variables to be declared before an assignment is made.

by tatsha Tag: Programming