All CADO systems up to that point had the system and CADOL interpreter reside in EPROM, so as soon as power was applied it read track 0 sector 0 of the diskette and began executing CADOL code. The IL codes for the interpreter written by Jim Ferguson looked similar to Tannenbaum's optimized IL codes from his empirical study. The language was extended by Richard Sexton, who added Pascal/C like syntax and 65 KB instead of 256 byte program overlay sizes. Previous to that, CADOL worked in programs no longer than 256 bytes of IL code long and when the programmers had code that hit about the 200-byte mark they would have to issue a LOAD statement to load the next 256 bytes of CADOL IL codes. At some point when a fair number of applications had been written, the loading of overlays was made transparent by Sexton's modifications to the interpreter up to an apparent program of 65 KB. Dan Lanham rewrote the compiler. This was all done in Intel 8085 assembly.
