The Free On-line Dictionary of Computing (30 December 2018):

hard-coded

    (By analogy with "hard-wired") Said of a data value
   or behaviour written directly into a program, possibly in
   multiple places, where it cannot be easily modified.  There
   are several alternatives, depending on how often the value is
   likely to change.  It may be replaced with a compile-time
   constant, such as a C "#define" macro, in which case a
   change will still require recompilation; or it may be read at
   run time from a profile, resource (see de-rezz), or
   environment variable that a user can easily modify; or it
   may be read as part of the program's input data.

   To change something hard-coded requires recompilation (if
   using a compiled language of course) but, more seriously, it
   requires sufficient understanding of the implementation to be
   sure that the change will not introduce inconsistency and
   cause the program to fail.

   For example, "The line terminator is hard-coded as newline;
   who in their right mind would use anything else?"

   See magic number.

   [Jargon File]

   (1999-10-18)