"We had written our [compiler] in STAR 0, the only assembler that Burroughs supported on the 205. Our compiler took one hour and 45 minutes to assemble. The first week of don's project he spent in writing his own assembler. He could assemble his compiler in 45 minutes. We were green with envy."

That's practical, right? He had limited computer time, and since every change meant a re-assembly, the obvious answer to quicker turnaround was to write a faster assembler...