Using ANSI Escape Sequences to Clear the Screen (67195)

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In real mode, the ANSI.SYS device driver is used to support ANSI escape sequences. It is installed in the CONFIG.SYS file with the following command:

   DEVICE=[drive:][path]ANSI.SYS
				

In protected mode, support for ANSI escape sequences come from an OS/2 AVIO ("advanced video input/output") function.

An ANSI escape sequence is a sequence of ASCII characters, the first two of which must be the escape character (char(27)) and the left-bracket character ([). The characters following the escape and left-bracket characters vary with the type of control function being performed.

An escape sequence cannot be entered directly at the system prompt because each ANSI escape sequence must begin with an escape character. If you press the ESC key, MS-DOS cancels the command line.

The following program uses the ANSI escape sequence (ESC[2J) to clear the screen:

      character*1 clrstr(4)
      data clrstr /' ','[','2','J'/ 
      clrstr(1) = char(27)            ! Escape character (ASCII 27).
      write (*,'(1x,4a1\)') clrstr    ! You must use a 1x as the first
      end                             ! part of the format specifier
                                      ! to ensure output of escape
                                      ! character.
				

The CHAR(int) intrinsic function is used to form either printing or nonprinting characters using the corresponding integer from the ASCII table.