The command line is a way to let the user call specific pieces of software to perform specialized tasks by typing simple commands on the keyboard. All computers that support a command line have program which presents the user with what is called a prompt. It is called a prompt because it prompts the user for input from the keyboard. In the picture below, the prompt is the part that looks like this:
c:\Documents and Settings\inetdaemon>
Windows XP uses a program called cmd.exe to produce the command prompt. Like most termal applications, the cmd.exe program understands a few commands that are completely internal to the program. Any command it does not understand it assumes is the name of another program located somewhere on the computer. The command line program will search a pre-defined set of paths through the computer's filesystem to find files located on the computer.
Microsoft Disk Operating System Command Line (MS-DOS prompt)
Windows NT, 2000, 2003, 95, 98, ME and XP systems:
Windows Vista, Windows 7 systems:
MS-DOS Prompt Window in Windows 7