Two big numbers to multiply

Description：

Input two numbers (A and B) which are overflow, then output answer (A * B).
My code is as follows:

// bigNumberToMultiply.cpp#include <stdio.h>#include <stdlib.h>#include <string.h>#include <conio.h>#include <time.h>#include <math.h>#define MAX_BIT 100 // The most bits is changed by changing MAX_BIT#define subtract48(a) a -= 48#define plus48(a) a += 48int main(){    // Initial arraies to store big number.    char num1[MAX_BIT], num2[MAX_BIT], numTemp[MAX_BIT][MAX_BIT], numFinal[2 * MAX_BIT + 2];    memset(num1, 0, sizeof(num1));    memset(num2, 0, sizeof(num2));    memset(*numTemp, 0, sizeof(numTemp));    memset(numFinal, 0, sizeof(numFinal));    int i = 0, j = 0, k = 0;    gets(num1);    gets(num2);    while (num1[i++]){        subtract48(num1[i - 1]);    }    while (num2[j++]){        subtract48(num2[j - 1]);    }    int bit1 = i - 2, bit2 = j - 2;    // Multiply by each bit    int more = 0;    for (i = bit2; i >= 0; i--){        for (j = bit1; j >= 0; j--){            numTemp[bit2 - i][bit1 - j] = (num1[j] * num2[i] + more) % 10;            more = (num1[j] * num2[i] + more) / 10;        }        numTemp[bit2 - i][bit1 - j] = more;        more = 0;    }    // To get final answer to numFinal    int maxBit, currentBit; //currentBit is for numFinal    for (i = 0; i <= bit2; i++){        j = MAX_BIT;        while (!numTemp[i][--j] && j >= 0);        maxBit = j;        if (maxBit != 0){            for (j = 0; j <= maxBit; j++){                currentBit = j + i;                numFinal[currentBit] += numTemp[i][j];                while (numFinal[currentBit++] > 9){                    numFinal[currentBit] += numFinal[currentBit - 1] / 10;                    numFinal[currentBit - 1] %= 10;                }            }        }    }    i = 2 * MAX_BIT + 2;    while (!numFinal[--i]);    for (i; i >= 0; i--){        plus48(numFinal[i]);        printf ("%c", numFinal[i]);    }    putchar ('\n');    system("pause");    return 0;}

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