Hi there and thank you for stopping by Hendro’s Workshop!
My name is Robertus Suhendro and in the place where I live, people are used to call me Hendro.
In 1984, I graduated with a major in applied physics. My thesis was building an instrumentation microcomputer for use in labs. IBM PC was available since 1981 but with the price tag of US$ 3.000, it was still pricey for most university labs to afford. My microcomputer was based on Z-80 microprocessor with BASIC interpreter and A/DC module that could be built with a fraction of the cost.
Fresh graduated, I joined an international computer company as a system programmer supporting their in-country data center. In mid 80, mainframe computers still ruled the world and they are connected with IBM SNA network protocol. The SNA network on mainframe that run VM (Virtual Machine) operating system was VNET (Virtual Network). One function of VNET was file transfer and emails.
The mainframe I supported was connected to mainframe in other country through an international leased line with the speed of 19.2 kbps (don’t laugh please: ). To conserve electric power, the mainframe was only in operation between 07:00 am and 22:00 pm, during week days only. This eventually created emails and files transfer queue backlog in our neighbor node who operated 24 hours. My manager asked me to find solution, other than the obvious 24 hours operation or the international bandwidth upgrade for this problem.
At that time, IBM VM operating system comes with its source code (S/370 assembler) so I could learn in detail the logic of its file transfer. I also happened to have a PC communication adapter that was originally bought for PC terminal emulator. My idea was to write a x’86 assembler program that controls the PC communication adapter and emulated what mainframe did when doing the file transfer. At night when mainframe was shutdown, the international leased line was switched to the PC so that file transfer could continue. It was switched back to mainframe in the morning so the normal mainframe to mainframe file transfer could resume while the PC also uploading the files it received during night time when the local mainframe was off. It was named VNET-PC.
Those were some that I did enjoy in early days. But then of course, corporate business life is totally different from life in a workshop. Career advancement, business requirements and management responsibilities drifted me away from my early passion.
Fast forward 30 years, I now look forward to retire from the corporate life. At the same time, the advent of maker movement, crowdsourcing, gig economy and tech startups fueled by proliferation of opensource culture is perfect sign that there is no better time to return back to my workshop life. With that in mind, I started Hendro’s Workshop to revive my youth’s passion, chronicle its activities and along the way to get acquainted with any of you who have the same passion and/or are taking the same journey.
Hope you have fun and learn something while browsing this pages!