I occasionally come across a sentence written as follows:

He wrote computer codes at home.

The "correct" way to say it would be like this:

He wrote computer code at home.

"Code" is used as a mass noun in computer science. Whether it be one line of code or a thousand, we still refer to it as "code". "Code", however, isn't the only word that has this problem.

"Data" is another word that is commonly used as a mass noun in computer science (which is seen more now pretty much everywhere). The following might sound a bit awkward to the average English speaker:

The data are being being sent.

We've grown accustomed to the following, however:

The data is being sent.

"Data", like "code", is used as a mass noun. The word "data" is actually the plural form of the singular "datum", hence the "are". It's a mass noun in the latter, in which it can only be used as a singular. This is the reason why "is" is used instead.

In both words above, the former example followed all the rules of grammar. The latter followed the favored convention (which changes as times change). You don't need to follow the rules strictly, but you need to adapt it in a way so that it makes sense to the majority of people.