max_size is defined as 50732. It is the size of the accumulator array.
int power : power = max number of digits allowed in one element of accumulator array.
int base : base = 10^power , it is the base in which the final and intermediate factorial results are represented.
int acc[max_size] : It contains the final and intermediate results of the factorials.
If we have to store a number x in the accumulator array , then we first represent it in the base defined above. That is x = base^n * an + base^(n-1) * a(n-1) ..... base^0 * a0
Then the accumulator value at index i is simply ai from the above expression. Doing this helps reduce the max_size of the accumulator array by 9 times (because each element now contains 9 times more digits).
void mult(int n) : Multiplies the number n with the acc array digit by digit. Takes the carry to the next digit. And stores the new product in the acc array only.
void fact(int n) : This function has a loop running from i = 1 to n , in each iteration it calls mult(i) which multiplies i to the accumulator array.
void set() : This function fills all the positions of the acc array by 0 and sets a[0]=1.This configuration is means that the acc array contains the number 1.And now on the mult() function can be used to multiply numbers in this array.
void display() : This function stores the values of the acc array from the index max_size-1 to 0 in a file fact.txt. This is the exact value of the factorial.
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acc set : It means that the main accumulator is initialised.
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fact calculated : It means that the value of the factorial is calculated and stored in the accumulator array.
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total units x : Here x means the number of elements of the accumulator array of size max_size which are actually used.
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saved in file : It means the factorial value is saved in fact.txt
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done : All steps completed and program ends successfully.
This function is tested to be able to calculate the exact values of factorials of n, where n can be upto 100,000. To calculate the factorial of 100,000 and store all its digits in the file fact.txt it takes about a minute.