help me trace this code

[sick]

 #include<stdio.h>
 #include<string.h>
 char r[6];
 unsigned result[156];
 unsigned temp[156];
 int len()
 {
 	int i;
 	for(i=0;i<=156;i++)
 	{
 		if(result[i]!=0)
 			break;
 	}
 	return 156-i;
 }
 void multiplication()
 {
 	int i,j;
 
 	memset(temp,0,sizeof(temp));
 
 	for(i=5;i>=1;i--)
 	{
 		for(j=155;j>155-len();j--)
 		{
 			temp[j+i-5]+=r[i]*result[j];
 		}
 	}
 	
 	for(i=155;i>=0;i--)
 	{
 		if(temp[i]>=10)
 		{
 			temp[i-1]+=temp[i]/10;
 			temp[i]%=10;
 		}
 	}
 
 	for(i=0;i<156;i++)
 	{
 		result[i]=temp[i];
 	}
  }
int main()
 {
 	int n;
 	int m;
 	int j;
 	int i;
 	int endPoint=156;
 
 	while(scanf("%s%d",r,&n)==2)
 	{
 		int bStartOutput=0;
 		int bInteger=1;
 		for(j=2;j>0;j--)
 		{
 			if(r[j]=='.')
 				break;
 		}
 		m=5-j;
 		m=m*n;
 
 		for(i=(j-1);i>=0;i--)
 		{
 			r[i+1]=r[i];
 		}
 		r[0]='0';

 		for(i=0;i<6;i++)
 		{
 			r[i]-='0';
 		}
        
 		memset(result,0,sizeof(result));
 
 		n--;
 		for(i=1;i<6;i++)
 		{
 			result[i+150]=r[i];
 		}
		
 		while(n--)
 		{
 			multiplication();
 		}
 
 		for(i=1;i<156-m;i++)
 		{
 			result[i-1]=result[i];
 		}

 		result[156-m-1]=100;

 		for(i=156-m;i<156;i++)
 		{
 			if(result[i])
 			{
 				bInteger=0;
 				break;
 			}
 		}

 		if(bInteger)
 		{
 			for(i=0;i<156;i++)
 			{
 				if(bStartOutput)
 				{
 					if(result[i]==100)
 						break;
 					else 
 						printf("%d",result[i]);
 				}
 				else if(result[i])
 				{
 					printf("%d",result[i]);
 					bStartOutput=1;
 				}
 			}
 		}
 		else
 		{
 			for(i=155;i>=0;i--)
 			{
 				if(result[i]==0)
 					endPoint=i;
 				else
 					break;
 			}
 			for(i=0;i<endPoint;i++)
 			{
 				if(bStartOutput)
 				{
 					if(result[i]!=100)
 						printf("%d",result[i]);
 					else
 						printf(".");
 				}
 				else if(result[i])
 				{
 					bStartOutput=1;
 					if(result[i]!=100)
 						printf("%d",result[i]);
 					else
 						printf(".");
 				}
 			}
 		}
 		
 	}
 }

my question in this program is in the function multiplication()
the line:

temp[j+i-5]+=r[i]*result[j];

how did that happen that the string array become integer without any conversion
and how that string of characters involved in multiplication with correct value....

[Zlatko]

Each character in the character array is really a one byte number. It will be treated as a one byte integer for the multiplication even though that's probably not what you want the program to do. What do you want the program to do?

[airhiphop]

 int len()
 {
 	int i;
 	for(i=0;i<=156;i++)
 	{
 		if(result[i]!=0)
 			break;
 	}
 	return 156-i;
 }

i < 156

[tabstop]

I have no idea what your point is. Does the following help illustrate the difference?

#include <stdio.h>

int main() {
    char number[10] = "123456789";

    printf("%c %c %c\n", number[2], number[5], number[8]); /*print the characters as characters*/
    printf("%d %d %d\n", number[2], number[5], number[8]); /*print the value of each character*/

    return 0;
}

[sick]

1 void multiplication()
2  {
3 	int i,j;
4 
5 	memset(temp,0,sizeof(temp));
6 
7 	for(i=5;i>=1;i--)
8 	{
9 		for(j=155;j>155-len();j--)
10 		{
11 			temp[j+i-5]+=r[i]*result[j];
12 		}
13 	}
14 	
15 	for(i=155;i>=0;i--)
16 	{
17 		if(temp[i]>=10)
18 		{
19 			temp[i-1]+=temp[i]/10;
20 			temp[i]%=10;
21 		}
22 	}
23 
24 	for(i=0;i<156;i++)
25 	{
26 		result[i]=temp[i];
27 	}
28 }

if you would scan that function multiplication... you would notice in line
11 temp[j+i-5]+=r[i]*result[j]; // the r[i] is use if you would scan the entire program
that is a character array and you would not get the right value because even if you
enter a character '1' in the array the value would be different because the equivalent
value of in ascii is 49...but if you trace that program...it is correct you check that
difference by putting this code after line 11 printf("%d",r[i]); //this would print the exact
character you enter...if you enter '1' then if you use that conversion (%d) it would print
1 instead of 49....umm pls. run the code so that you could understand me....

[Zlatko]

The digits of 'r' are converted from their ascii representation to the actual number of the digit in the main program at

        for(i=0;i<6;i++)
        {
            r[i]-='0';
        }

I don't understand why the first digit is always reset to '0' just before the conversion. See the line r[0]='0'; just before the conversion loop.

Does that answer your question?

[sick]

thanks zlatko...i missed that part