What is "dead code"

n. (context compilers English) instructions that, when executed, have no effect on the running of the program.

In computer programming, dead code is a section in the source code of a program which is executed but whose result is never used in any other computation. The execution of dead code wastes computation time and memory.

While the result of a dead computation may never be used, it may raise exceptions or affect some global state, thus removal of such code may change the output of the program and introduce unintended bugs. Compiler optimizations are typically conservative in their approach to dead code removal if there is any ambiguity as to whether removal of the dead code will affect the program output. The programmer may aid the compiler in this matter by making additional use of static and/or inline functions and enabling the use of link-time optimization.