In article <199604070321.TAA02171@myriad>, Matthew Ghio <ghio@myriad.alias.net> wrote:
Despite this, the Apple II never became a popular virus-writing platform. There are several possible reasons for this, but one of the main ones is that few Apple II users had hard disks. On the IBM PC, it was easy for a virus to get on the hard disk, then systematically infect every floppy disk put into the system. Apple II users, in contrast, often booted from floppies, and often rebooted when switching to a different software package, thus purging the virus from memory. (Pressing control-reset on the Apple II keyboard would always pull the reset line on the CPU, so it wasn't possible to trap the interrupt like it is possible to trap ctrl-alt-del on the PC.)
Not true. Pressing ctrl-reset jumped to the interrupt routine pointed to by the vector at (I think) 1010/1011, if the contents of that vector checksummed correctly with the contents of the next byte (1012), and otherwise reset the computer. It certainly was possible (and useful) to trap ctrl-reset. Also, even when a reset occurred, not all of the memory was cleared, so you could in fact keep code in memory across a reset, if you could arrange to have it run on the other side of the boot. As you pointed out, it was very easy to write viruses for the Apple ][. The "slave" disk layout contained two blank sectors (.5 K) within the DOS image that get loaded into memory. The designers may as well have labelled it "put virus here". - Ian "Been there; done that..."