A: As we know input to 
a program can come from a file, from the
console, or from a pipe or redirection. Examples of the latter are
     type text.dat | program
     program < text.dat
A Turbo Pascal program can be made to detect the redirections 
using
Interrupt 21Hex, function 44Hex, subfunction 00Hex. See PC 
Magazine
April 16, 1991, p. 374 for the code, and Duncan (1988), Advanced
MS-DOS Programming, pp. 412-413 for more information. 
Alternatively,
you can utilize the preprogrammed routines
  PIPEDIFN Is the standard input from redirection
  PIPEDNFN Is the standard output redirected to nul
  PIPEDOFN Is the standard output redirected
from my ftp://garbo.uwasa.fi/pc/ts/tspa3470.zip units.