RTFM =)

What is RTFM? I the beginning programmer and I know only one language... It is Pascal

RTFM = Read The F...ing Manuals =)
Read the FAQ - there you'll find out how to learn that an input stream has ended (in pascal these are the functions eof/eoln/seekeof/seekeoln)

I know this functions. All of them are intended for work with files! But my program should not use files, and should read from the keyboard and show on display... Or for this problem there is an exception?

Read in the FAQS :
How to write Pascal solutions

You are not right. These functions are intended to work not with files, but with input/output streams instead, which you can connect with keyboard/monitor. RTFM =)

while not eof do begin ... end;