What is the code to account for a user's erroneous input of the 'enter' key when the 'enter' key is not a menu item?

I'm certain this is a very simple programming question. I have awarded it the high number of points because it is somewhat urgent to me.  During a search on this site for another problem solution, I encountered the answer to this question.  But, unfortunately I cannot now retrace my steps to retrieve the necessary information to solve this problem.

Problem: User chooses to depress the 'Enter' key when presented with a menu list that does not include pressing the 'Enter' key w/o first selecting a menu choice.  
              In a section of the code during an 'else if' portion of a 'while' statement, I have accounted for incorrect non-menu item choices.  I simply do not see how  
              to allow for the 'Enter' key as an error in the program code.  

Program:

while (1)
//several if statements...              
program snipped for brevity...
else if //menu choice is not from the menu list accounted for here in program such as a zero input when zero is not a legitimate menu choice
                                                                                                                                                               (this portion answered/solved)
       if //the illegitimate menu choice is the 'Enter' key only
               what is the specific code to account for that error input? (here is the crux of this question)

As I did a Google search I thought I read that '\r' are the characters that C language recognizes as the 'Enter' key.  However, this code incorporated in the above 'else if' statement gives my Miracle C compiler a compilation error.

My environment: MS Windows XP Pro Multimedia Editionwith Service Pack 2 w/plenty of speed, memory & space.  As mentioned above, I am using the Miracle C Worbench.  I thank you in advance for your assistance.