System Error codes are errors and error codes that programmers are able to use when their software is having issues. They can be displayed by computers to users in response to software issues and hardware issues, or even certain kinds of user input. System error codes are typically presented as an acronym that includes an explanation of the error along with an explanation of what to do next.

These error codes are often seen on the internet when websites are not accessible or when an internal server issue occurs like the problem with a database. On local machines the error could be as simple as "file too long" which can be resolved by changing the name of the file, or more complex, like "no space left on the disk." In this scenario the user might need to close the program (to free swap file usage), delete some files, or buy an extra hard drive.

Other system problems can be as serious as "fatal error," where a program has essentially decided to quit and give up or even as minor as a warning that something isn't right with an operation. Most of the errors that occur on the GNU/Hurd system is reflected by an error code within the header file Errno.

These errors can be as simple as "text file busy," where the operation attempts to modify a read-only text file, or as complicated as "broken pipe." These errors can also mean that the function trying to run on the resource has been stopped by a signal like SIGPIPE and not properly dealt with.