refactoring: description for input handler functions

src/inputHandler.c

@@ -22,6 +22,7 @@ int getOperationId(char symbol) {
     return id;
 }
 
+// returns operation symbol for a specific operation id
 char getOperationSymbol(int id) {
     char symbol = ' ';
     switch (id) {
@@ -43,6 +44,7 @@ char getOperationSymbol(int id) {
     return symbol;
 }
 
+// Checking if operation id is available
 int isOperationValid(int id) {
     if(id < 0 || id > 7) return 0;
     return 1;