Something

#include <stdio.h>
#include <string.h>

int getline(char *);
void replace(char *, char *, int );

int main()
{
	char old_line[100];
	char new_line[200]="";
	int len;
	
	len = getline(old_line);
	replace(old_line, new_line, len);
	
	printf("%s\n", new_line);
	
	return 0;
}

int getline(char line[])
{
	int i, c;
	
	i = 0;
	while((c = getchar()) != 'q')
	{
	   line[i++] = c;
	}	    
	line[i]='\0';
	
	return i;
}

void replace(char old_line[], char new_line[], int len)
{
	int i, j;
	
	j = 0;
	for (i = 0; i < len; i++) {
	   if (old_line[i] == '\t') {
	       strcat(new_line, "  ");
	       j += 2;
        }
	    else {
            new_line[j++] = old_line[i];
        }
    }
}