refactoring: implemented descriptions for methods in arithmetic addition

src/arithmeticAddition.c

@@ -3,6 +3,7 @@
 #include <limits.h>
 #include <stdlib.h>
 
+// addition for two integer inputs (no decimal number)
 int* addition_integer(int num1, int num2) {
     if ((num2 > 0 && num1 > INT_MAX - num2) || (num2 < 0 && num1 < INT_MIN - num2)) {
         return NULL;
@@ -12,18 +13,21 @@ int* addition_integer(int num1, int num2) {
     return result;
 }
 
+// addition for two double inputs (decimal number)
 double* addition_double(double num1, double num2) {
     double* result = malloc(sizeof(double));
     *result = num1+num2;
     return result;
 }
 
+// addition for two float inputs (decimal number)
 float* addition_float(float num1, float num2) {
     float* result = malloc(sizeof(float));
     *result = num1+num2;
     return result;
 }
 
+// addition for two long inputs (no decimal number)
 long* addition_long(long num1, long num2) {
     long* result = malloc(sizeof(long));
     *result = num1+num2;