Multiply 2 million-digit numbers using files I/O

MultiplyMilion-File.c

//
//  simple.c
//  MultiplyX
//
//  Created by Pratik Anand on 02/12/13.
//  Copyright (c) 2013 Pratik Anand. All rights reserved.
//

#include <stdio.h>
#include <stdlib.h>

int main(int argc, const char * argv[])
{
    FILE *fp,*fp2,*fp3,*fp4;
    
    
    
    fp=fopen("/Users/pratikone/Code/number", "w");
    fp2=fopen("/Users/pratikone/Code/multiplier", "w");
    fp4=fopen("/Users/pratikone/Code/result", "w");
    
    
    int temp=0;
    for (int i=0; i<3000; i++) {
        temp=rand()%10;
        fputc(temp+'0', fp);
    }
    
    
    
    for (int i=0; i<600; i++) {
        temp=rand()%10;
        fputc(temp+'0', fp2);
    }
    
   
    
    
    struct timeval tv_start,tv_end;
    
    // insert code here...
    printf("Hello, World!\n");
    
    
    int lookup[10][10];
    //lookup table
    for(int l1=0;l1<=9;l1++)
        for (int l2=0; l2<=9; l2++) {
            lookup[l1][l2]=l1*l2;
        }
    
    //padding
    for (int dd=0; dd<10000; dd++) {
        //dSum[dd]='0';
        fputc('0', fp4);
    }
    
    
    fclose(fp);
    fclose(fp2);
    fclose(fp4);
    
    
    
    
    
    int nsize=3000;
    
    
    int msize=600;
    
    
    
    int ctrResJ=0;
    
    char c,d;
    
    
    
    int carry=0;
    int res=0;
    
    int d1=0,d2=0;
    
    int dCarry=0;
    int digit=0;
    
    int dTemp=0;
    int dRes=0;
    int realCtr=0;
    
    int real1=0,real2=0;
    
    
    gettimeofday(&tv_start,NULL);
    //tv_start.tv_sec ;// seconds
    //tv_start.tv_usec; // microseconds
    
    fp=fopen("/Users/pratikone/Code/number", "r");
    fp2=fopen("/Users/pratikone/Code/multiplier", "r");
    
    for (int ctr=0; ctr<=msize-1; ctr++) {
        
        fp3=fopen("/Users/pratikone/Code/temp", "w");
        
        for (int ctrNum=0;ctrNum<=nsize-1 ; ctrNum++) {
            
            
            fseeko(fp, (-1*ctrNum)-1, SEEK_END);
            fseeko(fp2, (-1*ctr)-1, SEEK_END);
            
            real1=fgetc(fp)-'0';
            real2=fgetc(fp2)-'0';
            res=real1*real2;
            
            //printf("%d*%d = %d\n",real1,real2,res);
            //res=lookup[number[ctrNum]-'0'][multiplier[ctr]-'0'];
            
            //adding the carry
            res=res+carry;
            
            carry=res/10;
            res=res%10;
            
            //printf("RESULT %c * %c = %d CARRY=%d\n",number[ctrNum],multiplier[ctr],res,carry );
            
            //result[ctrResJ++]=res+'0';
            fputc(res+'0', fp3);
            
            //printf("\n in file: %c\n",res+'0');
            
            res=0;
            
        }
        
        if(carry>0){
            //printf("\ncarry: %c\n",carry+'0');
            fputc(carry+'0', fp3);
            //result[ctrResJ++]=carry+'0';  //last carry
            carry=0;
        }
        
        //result[ctrResJ++]='\0';
        fclose(fp3);
        
        
        ctrResJ=0;
        
        
        //add
        
        d2=0;
        fp3=fopen("/Users/pratikone/Code/temp", "r");
        fp4=fopen("/Users/pratikone/Code/result", "r+");
        while ((c=fgetc(fp3))!=EOF) {
            //printf("\nRead from fp3 %c \n",c);
            digit=c-'0';

           
            fseeko(fp4, d2+realCtr, SEEK_SET);
            //printf("\nLocation:%ld\n",ftell(fp4));
            d=fgetc(fp4);
            //fclose(fp4);
            
            
            dTemp=d-'0';
            
            //printf("\ndTemp %d \n",dTemp);
            //dTemp=dSum[d2+realCtr]-'0';
            
            dRes=(dTemp+digit+dCarry);
            //printf("\ndRes %c \n",(dRes%10)+'0');
            
            //fp4=fopen("/Users/pratikone/Code/result", "w");
            fseeko(fp4, d2+realCtr, SEEK_SET);
            fputc((dRes%10)+'0', fp4);
            //fclose(fp4);
            
            
            

            //dSum[d2+realCtr]=(dRes%10)+'0';
            dCarry=dRes/10;
            d2++;
        }
        
        
        
        if(dCarry>0){
            //fp4=fopen("/Users/pratikone/Code/result", "w");
            fseeko(fp4, d2+realCtr, SEEK_SET);
            fputc(dCarry+'0', fp4);
            //fclose(fp4);

            
            //dSum[d2+realCtr]=dCarry+'0';  //last carry
            dCarry=0;
            d2++;
        }
        //copying for knowing the final end
        d1=d2+realCtr;
        
        d2=0;
        
        //printf("Result is %s\n",dSum);
        
        
        realCtr=realCtr+1;

        fclose(fp3);
        if (ctr==msize-1) {
            fputc(EOF, fp4);
        }
        
        fclose(fp4);
    }
    
    
    fclose(fp);
    fclose(fp2);
   
    
    
    
    gettimeofday(&tv_end,NULL);
    printf("\nTime taken :%ld sec\n",tv_end.tv_sec-tv_start.tv_sec);
    printf("\nTime taken :%d us\n",tv_end.tv_usec-tv_start.tv_usec);
    
  
    
    
   
    
    return 0;
}