data structures - How to implement retrieve and update in a C struct -

Suppose we have the following structure in C:

  ; Four names [50]; Four nickname [50]; Four courses [50]; };   
 Any person can retrieve  (R, C, S)  and  updates (R, C, S) .  
 
  Retrieve ()   R  a 
 Structure student ,  s  An indicator for this would be the value of this field in the area of ​​ struct  and  C .  
  Update ()    then  Structure student , an indication for  s   Struct is a field of  and finally the value of  c  in the field  struct . Since you are limited to using C, your options are limited.  
 In fact, there are two different options (assuming you do not want to dive into memory / pointers magic):  
 
 Your data on the basis of the actual type Create alternate functions to set / retrieve  
 Create your own "version" datatype as a  struct .   
 
 Using the Dispute Hire Function, you can do something like this:  
  Recover vowel intent (Constant Student Student Dataset, Const char * Field, int * value) {ifet! (! Dataet ||! Field ||! Value) // some minor error checking return; If (! Strcmp (field, "AM")) {* value = dataet-> AM; Return; } Printf ("tried to recover unknown integer field '% s'! \ N", field); }   
 Receiving stars or setting integers will work in the same way by using their jobs.  
 Using custom version datatype:  
  structure type {char type; Union {four strings [50]; Integer integer; }; }; Recover empty (Constructor Student * Dataset, Constant * Field, Straight Variient * Value) (If (! Dataset ||! Field ||! Value) // Some minor error check returns; If (! Strcmp (field, "AM" ); {Value-> gt; 0; // Suppose it represents an integer value value-> integer = dataset-> gt; return;} printf ("Unknown integer field '% s' Tried to recover! \ N ", field);} int varToInt (in struct version * Not) {if (value- & gt; type == 0) return Value- & gt; integer; Else // 0 not an integer value return;}