start point data type modification

src/main/c/Calculator/calculator.c

@@ -2,10 +2,10 @@
 
 // Function prototypes
 void displayMenu();
-int add(int num1, int num2);
-int subtract(int num1, int num2);
-int multiply(int num1, int num2);
-int divide(int num1, int num2);
+double add(int num1, int num2);
+double subtract(int num1, int num2);
+double multiply(int num1, int num2);
+double divide(int num1, int num2);
 double exponent(double base, double exponent);
 double modulus(double num1, double num2);
 double logarithm(double num);
@@ -16,9 +16,8 @@ double sine(double angle);
 double cosine(double angle);
 double tangent(double angle);
 
-
 int main() {
-    int choice, num1, num2, result;
+    double choice, num1, num2, result, angle;
 
     do {
         displayMenu();