Computer programming (often shortened to programming or coding) is the process of writing, testing, and maintaining the source code of computer programs. The source code is written in a programming language. This code may be a modification of existing source or something completely new, the purpose being to create a program that exhibits the desired behavior. The process of writing source code requires expertise in many different subjects, including knowledge of the application domain, specialized algorithms, and formal logic. Within software engineering, programming (the implementation) is regarded as one phase in a software development process. In some specialist applications or extreme situations a program may be written or modified (known as patching) by directly storing the numeric values of the machine code instructions to be executed into memory.
There is an ongoing debate on the extent to which the writing of programs is an art, a craft or an engineering discipline. Good programming is generally considered to be the measured application of all three: expert knowledge informing an elegant, efficient, and maintainable software solution (the criteria for “efficient” and “maintainable” vary considerably). The discipline differs from many other technical professions in that programmers generally do not need to be licensed or pass any standardized (or governmentally regulated) certification tests in order to call themselves “programmers” or even “software engineers“.