If a program is no longer needed, it can be deleted from OpenGL memory by calling glDeleteProgram, providing the program handle as the only argument. This invalidates the handle and frees the memory used by the program. Note that if the program object is currently in use, it will not be immediately deleted, but will be flagged for deletion when it is no longer in use.
Also, the deletion of a shader program detaches the shader objects that were attached to the program but does not delete them unless those shader objects have already been flagged for deletion by a previous call to glDeleteShader. Therefore, as mentioned before, it is a good idea to detach and delete them immediately, as soon as the program is linked, ...
