If we're talking about errors in the Sinclair Spectrum's ROM, there are lots of little ones which do not warrant mention here, some mysterious, never-executed code left over from the development process, and a few larger anomalies which merit further discussion. The feature whereone one could hold down a keyword key and rapidly fill the screen with RANDOMIZE RANDOMIZE RANDOMIZE RANDOMIZE etc was a bug, although a mesmerising one.

Firstly, there was the famous '-65536' bug, in which a muddle over the treatment of 8-bit numbers resulted in 'PRINT INT -65536' returning '-1' on all models of Spectrum.

Secondly, at the 'Scroll?' prompt, if you typed'Caps Lock', 'True Video' and some of the other function keys, the screen would quickly fill with random nonsense dragged from the memory addresses of the character set onwards, followed by an 'Invalid Colour' error.

Thirdly, on a 128k or later machine, typing 'FLASH 1' into Sinclair 128K BASIC caused the text to flash - which is expected - but it also caused the Spectrum's menu system to flash, as well. Yes, long before BLINK came and went, there was FLASH. FLASH was better.

Most amusing of all, however, was the suicidal 'Invalid Device Expression, 1000:1' error - an error message which could appear under certain circumstances when using a 128k machine with an Interface 1. It's one character longer than a single line, and when it is displayed it overflows the screen and causes the machine to crash; thus it is an error message which itself causes an error.

Bloody all of the bastards:
http://www.nonowt.com/magfold/articfol/bugs_in.html