====Welcome to Bignum!====

So the semester's winding down and Bignum is done. I don't think my solution was very intuitive; the two numbers are character arrays. There program works however and was a brilliant testing of pointer and array manipulation with a small amount of struct fun I threw in at the end for practice. The struct does nothing(the program works without it), but served as a quaint tutorial for what's to come later. Overall, I'm pleased with the result. bignum location is @ /home/asowers/src/cprog/new_bignum BONUS: check out option 5
====Code====

bignum.c
<code c>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "add.h"
#include "multiply.h"
#include "sub.h"
#include "divide.h"

struct {
        char *first;
        char *second;
        int length;
        int count;
        int div;
}n;

int main()
{

	int select=1;

	printf("Welcome to BigNum!\n");
	printf("select a length for your array size: ");
	scanf("%u", &n.length);
	n.length = n.length-1;
        n.first = (char*)malloc(sizeof(char)*n.length);

        printf("\nFirst number: ");

        fgetc(stdin);
        for(n.count = n.length; n.count >= 0; -- n.count)
        {
                n.first[n.count] = fgetc(stdin);
                n.first[n.count] = n.first[n.count] - 48;
        }


 	n.second = (char*)malloc(sizeof(char)*n.length);

        printf("\nSecond number: ");

        fgetc(stdin);
        for(n.count = n.length; n.count >= 0; -- n.count)
        {
                n.second[n.count] = fgetc(stdin);
                n.second[n.count] = n.second[n.count] - 48;
        }

	while(select != 0 ){
		printf("_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_\n");
                printf("|Please choose an Option(1-5): |\n");
                printf("|Option 1: Add                 |\n");
                printf("|Option 2: Subtract            |\n");
                printf("|Option 3: Multiply            |\n");
                printf("|Option 4: Divide              |\n");
		printf("|Option 5: Exit                |\n");
                printf("-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-\n");
		scanf("%d", &select);
                if (select == 1){
			printf("\nYou selected addition.\nThe answer is: ");
			n.first = add(n.first, n.second, n.length);
			for (n.length; n.length>=0; --n.length)
		        {
        	        	printf("%hhu", n.first[n.length]);
        		}
			printf("\n");
			break;}
		else if (select == 2){
			printf("\nYou selected subtraction.\nThe answer is: ");
			n.first = sub(n.first, n.second, n.length);
			for (n.length; n.length>=0; --n.length)
        		{
	                	printf("%hhu", n.first[n.length]);
        		}
			printf("\n");
                        break;}
		else if (select == 3){
			printf("\nYou selected multiplication.\nThe answer is: ");
			multiply(n.first, n.second, n.length);
			for (n.length; n.length>=0; --n.length)
                        {
	                        printf("%hhu", n.first[n.length]);
                        }
			printf("\n");
                        break;}
		else if (select == 4){
			printf("\nYou selected division.\nThe answer is: ");
			divide(n.first, n.second, n.length, &n.div);
			printf("%hhu", n.div);
			printf("\n");
			break;}
		else if (select == 5){
			printf("\nYou selected to exit.\nThe answer is: Tom's mom");
			break;}
		else{
                        printf("Incorrect in.\n");
		}
	}
	printf("\nGoodbye!\n");
        return(0);
}
</code>

add.h
<code c>

#ifndef _ADDITION_H
#define _ADDITION_H
char * add(char * first, char * second, int length)
{
        int count = 0;
	char carry = 0;

        for(count; count <= length; ++count)
        {
                int holder = (first[count] + second[count])+carry;
                if (holder > 9)
                {
                first[count] = holder-10;
                carry=1;
                }
                else
                {
                first[count] = holder;
                carry=0;
                }
        }

        return first;
}

#endif
</code>

sub.h
<code c>
#ifndef _SUB_H
#define _SUB_H

char * sub(char *first, char *second, int length)
{

        char count = 0;

        for(count; count <= length; ++count)
        {
                if (first[count] < second[count])
                {
                        first[count+1] = first[count+1] - 1;
                        first[count] = first[count] + 10;
                }

                first[count] = first[count] - second[count];
        }

        return first;
}
#endif
</code>

multiply.h
<code c>
#ifndef _MULTIPLY_H
#define _MULTIPLY_H
#include <math.h>
#include "sub.h"

void multiply(char * first, char * second, int length)
{
        int count = 0;
        int holder = 0;
        char *third;
	third = (char*)malloc(sizeof(char)*length);

        for (count; count <= length; ++count)
        {
                third[count] = first[count];
        }
        for(count=0; count <= length; ++count)
        {
                holder = (second[count]*pow(10, count));
                for(holder; holder > 0; --holder)
                {
                        first = add(first, third, length);
                }
        }

        first = sub(first, third, length);

}

#endif
</code>

divide.h
<code c>
#ifndef _DIVIDE_H
#define _DIVIDE_H

void divide(char * first, char * second, int length, int *div)
{
        int count = 0;
        char *fourth;

	 fourth = (char*)malloc(sizeof(char)*length);

        for (count; count <= length; ++count)
        {
                fourth[count] = first[count];
        }

        for(count=length; count>=0; --count)
        {
                while(first[count] > 0)
                {
                        ++*div;
                        first = sub(first, second, length);
	        }
         }
}

#endif
</code>

compiling and implementation
<cli>
lab46:~/src/cprog/new_bignum$ gcc bignum.c -o bignum -lm
lab46:~/src/cprog/new_bignum$ ./bignum
Welcome to BigNum!
select a length for your array size: 4

First number: 1234

Second number: 0100
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
|Please choose an Option(1-5): |
|Option 1: Add                 |
|Option 2: Subtract            |
|Option 3: Multiply            |
|Option 4: Divide              |
|Option 5: Exit                |
-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
1

You selected addition.
The answer is: 1334

Goodbye!
lab46:~/src/cprog/new_bignum$ ./bignum
Welcome to BigNum!
select a length for your array size: 5

First number: 09999

Second number: 00001
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
|Please choose an Option(1-5): |
|Option 1: Add                 |
|Option 2: Subtract            |
|Option 3: Multiply            |
|Option 4: Divide              |
|Option 5: Exit                |
-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
1

You selected addition.
The answer is: 10000

Goodbye!
Welcome to BigNum!
select a length for your array size: 5

First number: 00400

Second number: 00050
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
|Please choose an Option(1-5): |
|Option 1: Add                 |
|Option 2: Subtract            |
|Option 3: Multiply            |
|Option 4: Divide              |
|Option 5: Exit                |
-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
3

You selected multiplication.
The answer is: 20000

Goodbye!
lab46:~/src/cprog/new_bignum$ ./bignum
Welcome to BigNum!
select a length for your array size: 4

First number: 5250

Second number: 0050
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
|Please choose an Option(1-5): |
|Option 1: Add                 |
|Option 2: Subtract            |
|Option 3: Multiply            |
|Option 4: Divide              |
|Option 5: Exit                |
-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
4

You selected division.
The answer is: 105

Goodbye!
lab46:~/src/cprog/new_bignum$ ./bignum
Welcome to BigNum!
select a length for your array size: 1

First number: 1

Second number: 1
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
|Please choose an Option(1-5): |
|Option 1: Add                 |
|Option 2: Subtract            |
|Option 3: Multiply            |
|Option 4: Divide              |
|Option 5: Exit                |
-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
5

You selected to exit.
The answer is: Tom's mom
Goodbye!
lab46:~/src/cprog/new_bignum$ 

</cli>