x120.c

/* Exercise 1-20.
 * Write a program detab that replaces tabs in the input with the proper number
 * of blanks to space to the next tab stop. Assume a fixed set of tab stops,
 * say every n columns. Should n be a variable or a symbolic parameter?
 */

#include<stdio.h>
#define n 4

main()
{
    int c,i = 0;

    while ((c=getchar())!=EOF)
    {
        if (c == '\t')
        {
            /* every tab must be replaced by at least one space */
            putchar(0x20);
            /* additional spaces put until tab stop is reached */
            while(++i%n) putchar(0x20);
        }
        else
        {
            /* normal char piping */
            putchar(c);
            i++;
        }
        if (c == '\n') i=0;
    }
}

			/* This line starts with 3 tabs */