Write a program entab that replaces strings by the minimum number of tabs and blanks to achieve the same spacing.Use the same tab stops as for detab.When either a tab or a single blank would suffice to reach a tab stop, which should be given preference?

#include <stdio.h>

#define TABINC       8    /*tab increment size */

/* replace strings of blanks with tabs and blanks    */
int main(){
      int c, nb, nt, pos;

      nb = 0;                 /* # of blanks necessary */
      nl =0;                 /* # of tabs necessary    */
      for (pos = 1; (c =getchar()) != EOF; ++pos)
           if (c == ' '){
              if (pos % TABINC != 0)
                    ++nb;                /* increment # of blanks */
              else{
                  nb = 0;       /*reset # of blanks */
                  ++nt;         /* one more tab     */
              }
           } else {
                 for(; nt > 0; --nt)
                      putchar('\t');   /*output tab(s)  */
                 if(c == '\t')    /* forget the blank(s)  */
                       nb = 0;
                 else            /* output blank(s) */
                     for (; nb > 0 ; --nb)
                           putchar(' ');
                putchar(c);
                if(c == '\n')
                     pos = 0;
                else if (c == '\t')
                      pos = pos +  (TABINC - (pos -1) % TABINC) - 1;
           }
}