HLPWWW (Version 8.7d) JESS copyright (C) 1985-2018 Licensee : Webmaster, Murdoch University, Australia Welcome. Tuesday, 19-Mar-19 14:09 To adapt to different sizes of VDU screen and printed page, JESS stores the number of lines applicable in each case in two places. The first of these applies by default to all JESS users at your site; the information comes from a file called SYSDFT.BAT that is usually located in the JESS directory called ZIP/. Under certain computer operating systems, these default values can be changed by users, the new ones then applying (to themselves only) for the duration of their session on the computer (i.e. per login). The standard JESS environment commands to change the number of lines of output are "VDULIN nn" and "PRNLIN nn" which are typed at the operating system prompt (without quotes), where "nn" is an appropriate number of lines, generally between 20 and 80. These commands are not implemented under the DOS operating system. In this case you may be able to change the SYSDFT.BAT file but this is not recommended by us. Alternatively, you may be able to set the environment variable "JPAG" in your AUTOEXEC.BAT file. The latter action is better than the former but still undesirable!
More than one version of JESS may be present on some computer systems. In such cases, one of these versions will be established as the default; this will be the one relevant to most users and it will be accessed automatically. It is possible to switch between different versions of JESS (if available) using the 'JTD' command (for 'JESS top directory'). You must know the (site-specific) location of the directory holding the version of JESS you want to access. This directory name is given as an argument on the JTD command. For example, > JTD \Jess\V60
Using so-called 'environment variables', the computer operating system passes various items of data to JESS programs immediately following their execution. This provides the programs with site-specific information such as user authorisation codes, default parameters and non-standard settings. The relevant variables are as follows: JESS - top directory specification (used by the JTD command) JUSR - Licensee identifier JCHK - authorisation check-sum JBLD - database builder identification JBOS - home/remote site identifiers and boss initials; Greenwich offset JPAG - default lines per page (VDU and printer) JSPC - non-standard JESS special characters (four of them) ISSU - issue specification of current JESS software package These environment variables are usually set at the commencement of the computer session by an automatically-executed command script (in AUTOEXEC.BAT with DOS or .login with Unix).