Mac Plus Clock

News

After reading David Cantrell's page on his Mac Plus Clock I decided to make my own with an old Mac Plus that a friend gave me some years ago. It has previously been used to hold up shelves and as a door-stop. Truly it is a multi functional device. There were however, a few problems.

First off I didn't have an operating system for the Plus. It has no HDD so must boot off a floppy disk. An 800K floppy disk. You can't write one of those in a PC floppy disk drive. Fortuantly, I had recently aquired several older Macs from an ebay auction, I got them for a song :) After much shouting at them I managed to get an old LC475 with 20Megs of RAM and an 80 Meg HDD going. It also had a 10 base-T NIC in it which also worked. I was cooking with gas. I formatted my only DoubleDensity floppy disk to Mac format, downloaded System Software 6.0.3 worte it to the disk and crossed my fingers. Of course the sturdy Mac Plus booted 1st time, the problem was that with SSW 6.0.3 I only had 33k left on my floppy disk. The O'Clock software that David had used was bigger than this, and it also required System 7 or above. There was no way I was going to be able to get System 7 onto an 800K floppy, and no way I was going to be able to use a ZIP drive as David had, since I only have a 250Mb SCSI ZIP drive, and after many hours of screaming and abusing the MacOS I knew that was a non starter.

So, how to proceed? I decided that since all I wanted was a program to display the time on the screen, how hard could it be? I downloaded the Macintosh Programmers Workshop from apple onto my LC475 and began in earnest. Working in C it wasn't actually that hard to get the date appearing, and I managed to edit one of the example programs to do something like what I wanted in a few hours. Strings are a bit funny on MacOS, they store their length in the first byte, a bit like Pascal, which confused me a little bit initially. So after a few bug fixes and long compiles on the LC I copied my executable to the 800K floppy I had 6.0.3 on, it was 33K so I had just enough space. I booted the Plus and opened my program. It crashed, horribly.

After much searching and investigation it appeared that I was making some calls that required a colour quickdraw version, which the Plus doesn't have, since it can only do two colours. Once I replaced the calls with their mono varients the program ran fine on the plus, after some minor bug fixes to fix the screen blanking I was finished.

You can see some pictures of the Plus here