Commenting code is the process of adding normal English statements to source code. This is done for several reasons. The first is to clarify a confusing block of code, or a particularly tricky section of code. A second reason why commenting is done is for documentation. Commenting the preconditions and postconditions as well as the purpose of all functions, method, procedures, or any named block of code allows for them to be reused without having to read the code. Commenting code is suppose to be done while coding. In practice this is rarely done. Comments if added at all are added after the fact.

The syntax for a comment in code will change from language to language all most all imperative programming languages have comments in some form. Commenting types can come in three forms depending on the language. The first main type is "unique line only". This type of comment can only be written on a line by itself. It can not share a line with a normal executable statement. An example of this is found in ADA. The second main type of comment is “anywhere” comments. These comments can be placed anywhere within code. C and Java both support this type of commenting with the /* and */. The third and finally common type of comments comes in the form of "end of line". These comments an be on the same line as an executable statement but only to the right of the statement. An example of this is C++ and Java with //. Pascal is a language that encourages "end of line" style.