                              HYDRA 5R4 
SPACE 18
CENTER HYDRA
SPACE   
CENTER Terminal Sharing Optimiser   
CENTER Level 5R4
0                           Written by  John Walker   March 1975
0                           Modified by Mike Darnell  January 1980  
1Purpose.   
0      This program provides a facility by which many users may 
0      share a single terminal, or a single terminal may be used
0      by a hydra-headed systems programmer to control a
0      multitude of runs.  The program uses RSI$ to pass images 
0      to and receive images from, the various subsidiary runs. 
0      If you have any problems, contact Michael Darnell at 
0         Unisys Corporation
0         2290 Science Parkway  
0         Okemos, MI 48864  
0      or Mike.Darnell@usa.net  
1Use.   
0      The terminal sharing optimiser is activated by:  
0   
0      @HYDRA   
0   
0      HYDRA will then accept input from the terminal.  CLIST mode  
0      is entered to register a list of control statements  
0      processed by HYDRA.  These statements are as follows:
2@LOGIN CHAR
0      This statement activates a site code and defines the single  
0      ASCII character CHAR as the terminal identifier for that 
0      site.  Input may then be typed in for that terminal by   
0      prefixing each input line with the specified CHAR.  All  
0      output for that site will be typed out prefixed by CHAR  
0      and a space. 
2@LOGOUT CHAR   
0      This statement deactivates the site code defined by the  
0      ASCII character CHAR as the terminal identifier for that 
0      site.  All connections between the run and the specified 
0      site are destroyed.  
2@ASSUME<,L>   CHAR<,@ replacement> 
0      This statement dedicates the input to the terminal   
0      identified by CHAR.  Once the @ASSUME statement has been 
0      entered, all input typed to the terminal which does not  
0      begin with an at-sign (@) will be directed to the specified  
0      terminal.  Input beginning with an at-sign will continue to  
0      interpreted as HYDRA commands.   
0         To enter a control statement to the @ASSUME'd terminal,   
0      it is necessary to have a character which will substitute
0      an at-sign in column 1.  The <@ replacement> serves this 
0      purpose.  The default <@ replacement> is a colon (:).  If a  
0      colon is not wanted, an alternative <@ replacement> may be   
0      specified in the <@ replacement> field of the @ASSUME
0      command. 
0         The 'L' option will cause an automatic @ECHO of the newly 
0      @ASSUME'd terminal to be done.  If the 'L' option is not 
0      specified, no @ECHO will be done.
0         @ASSUME mode may be terminated and HYDRA reverted to the  
0      use of leading terminal identifiers by the command : 
0   
0      @ASSUME,N
2@STATUS
0      The @status statement will type the identification   
0      characters and site codes for all active terminals.  
2@ECHO CHAR 
0      The @ECHO statement will retype the last inputs and outputs  
0      of the terminal identified by CHAR.  
2@ENDX  
0      The @ENDX statement will cause an exit from HYDRA.   
0      To reenter HYDRA, use the statement :
0   
0      @HYDRA   
0   
0      This will cause HYDRA to be reactivated, and all 
0      previously defined terminals to be accessable.   
0      HYDRA uses a temporary file named HYDRA$runid to 
0      save its environment in.  If this file is @FREEd,
0      no recovery is possible. 
