Redundant code
Redundant code is a computer programming term for code in a computer program that is redundant in some way. For instance, recomputing a value that has previously been calculated and is still available, or code that is never executed.
Redundant code elimination is a form of compiler optimization in which redundant computations are removed from a program. The redundant code elimination technique is in the same class of optimizations as unreachable code elimination and dead code elimination.
Example
int f (int x)
{
int y=x*2;
return x*2;
}
The second x*2 expression is redundant code and can be replaced by a reference to the variable y. Alternatively the definition int y=x*2 can instead be removed.
Alternate uses of the term
Redundant code may also be used to refer to code that is executed but has no effect on the output of a program - however this is usually known as dead code. A NOP might be considered to be redundant code that has been explicitly inserted to pad out the instruction stream or introduce a time delay. Identifiers that are declared but never referenced are usually termed as redundant declarations. [citation needed]