Enhance comments and variable initialization in factorial.c

Added comments for clarity and improved code readability.

Author: swahathi

math/factorial.c

@@ -1,30 +1,36 @@
-#include <stdio.h>
+/*
+ Program to compute factorial of large numbers using array storage.
+ Handles values beyond standard integer limits.
+*/
+#include <stdio.h> //for basic functions like printf,scanf etc
 int main()
 {
-    int a[200], n, counter, temp, i;
-    a[0] = 1;
-    counter = 0;
+    int a[200], n, counter, temp, i;      //initialize variables and arrays
+    a[0] = 1;    //first element of the array to be 1
+    counter = 0;    //to track number of digits in result
     printf("Enter a whole number to Find its Factorial: ");
-    scanf("%d", &n);
-    if (n < 0)
+    scanf("%d", &n);    //take input number and store to variable n
+    if (n < 0)    //factorial not defined for negatives
         printf("Cannot Calculate factorials for negative numbers.");
     else
     {
         for (; n >= 2; n--)
         {
-            temp = 0;
+            temp = 0;    //for carry during multiplication
             for (i = 0; i <= counter; i++)
             {
-                temp = (a[i] * n) + temp;
-                a[i] = temp % 10;
-                temp = temp / 10;
+                temp = (a[i] * n) + temp;    //multiply digit and add previous carry
+                a[i] = temp % 10;    //store last digit of result
+                temp = temp / 10;    //update carry 
             }
+            //store remaining carry digits in array
             while (temp > 0)
             {
                 a[++counter] = temp % 10;
                 temp = temp / 10;
             }
         }
+        //print factorial in msd order 
         for (i = counter; i >= 0; i--) printf("%d", a[i]);
     }
     return 0;