Overhead code is the additional (or excess) object code

Object code

Object code, or sometimes object module, is what a computer compiler produces. In a general sense object code is a sequence of statements in a computer language, usually a machine code language....

 generated by a compiler to provide machine code

Machine code

Machine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...

 which will be executed by a specific CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

. This code includes translations of generic instructions listed in cross-platform

Cross-platform

In computing, cross-platform, or multi-platform, is an attribute conferred to computer software or computing methods and concepts that are implemented and inter-operate on multiple computer platforms...

 code, and is tailored for execution on a specific platform or architecture. An example of overhead code would be code generated to handle reference counting

Reference counting

In computer science, reference counting is a technique of storing the number of references, pointers, or handles to a resource such as an object, block of memory, disk space or other resource...

, while source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

 written in a high level language is an example cross-platform code.

Analogy

The coverage area of a standalone house is more than the space taken by enclosures. Similarly, overhead code is the part of the program which is not listed in the source code. However, it is needed for the software to operate properly.