Mac to Mainframe
Volume Number: 6
Issue Number: 6
Column Tag: C Workshop
Mac to Mainframe With HyperCard 
By John R. Powers, III, Monte Sereno, CA
Note: Source code files accompanying article are located on MacTech CD-ROM orsource code disks.
[John Powers designs and programs computer software tools for people who are
not computer experts. In his 23 years of software development experience, Mr.
Powers has developed products ranging from portable computers for business
executives to educational games for children. Mr. Powers has been employed by
Battelle-Columbus Laboratories, the Authorship Resource Inc., Atari, Convergent, and
the Learning Company. In 1988, he formed Easy Street Software. His most recent
projects have been developing software for the Mac-to-NonMac connection using C and
HyperTalk.]
Trapping the Wild XFCN
Little did I know that the phone call would lead me on an adventure with the
biggest and wildest XFCN’s I’ve ever done. It all started when Tri-Data Systems wanted
to do something special with their Mac-to-Mainframe connection.
The Mac-to-Mainframe Connection
Mac communications with IBM mainframes has become one of the “hot” market
areas for the Macintosh. Large corporate users of IBM mainframes have discovered the
Macintosh and want to use the Macintosh with their mainframes. They try the
terminal emulators on their Macintosh for the mainframe tasks that they have always
done, but they become frustrated that they can’t enjoy the full power and flexibility of
the Macintosh interface. They enjoy using HyperCard for their other tasks and want to
use HyperCard for their mainframe communication as well. Mainframe users are
e specially frustrated when they want to customize their interaction with the
mainframe and can’t use the capability of HyperCard. They were asking major
communication hardware and software suppliers like Tri-Data Systems why they
couldn’t use HyperCard.
The HyperCard-to-Mainframe Connection
Tri-Data Systems had completed a Mac-based programmatic interface to IBM
mainframes and wanted to extend that capability to HyperCard. Using a HyperCard
stack, a user should be able to use or write handlers through which a stack could
communicate with an IBM mainframe. Traditional communication methods require a
dedicated terminal emulator or a custom application program, but Tri-Data Systems
wanted more: a HyperCard interface that would greatly simplify the development of
custom interfaces by giving the user a powerful set of HyperCard tools combined with
extensions for IBM mainframe communication. Handlers could be written that provide
a one-button “logon” and use HyperCard fields to store and retrieve mainframe data.
Complete transactions could be automated using HyperCard.
The HyperCard XCMD/XFCN capability was the logical way to extend HyperCard
into the arena of IBM mainframe communication. The XCMD/XFCN interface would be
the linkage between HyperCard and Tri-Data’s driver. This relationship is shown in
figure 1, “The HyperCard-to-Mainframe Connection”.
Figure 1.
Referenced by (2):