Redirection and Piping

This section covers redirection and piping.  You can use these features to 
change how CMD.EXE and some application programs handle input and output. 

Internal commands and many external programs get their input from the 
computer's standard input device and send their output to the standard 
output device.  Some programs also send special messages to the standard 
error device.  Normally, the keyboard is used for standard input and the 
video screen for both standard output and standard error. 

Redirection and piping allow you to change these assignments temporarily. 

Redirection changes the standard input, standard output, or standard error 
device for a program or command from the default device (the keyboard or 
screen), to another device or to a file. 

Piping changes the standard output and / or standard error device so that 
the output of one command becomes the standard input for another program 
or command.