Will ubuntu run on an 18 bit system?

18 bit doesn't exists, bits com in powers of 2. If the system ran windows 98, it will be a 32bit system. 16bit CPUs are circa 1975 and systems around that time are not powerful enough to run windows 3.1, let alone 98

Thanks Ian Ace, that solved my question.

While I am sure your answer is correct wrt. Ubuntu Linux, your assertion that #bits come in powers of 2 is incorrect, if you go back in history in computing. Just FYI, back in the day, there were several DEC (Digital Equipment Corporation) computers that had register/accumulator and word sizes that were multiples of 2, but not powers of 2. The PDP-7 and PDP-9 computers had 18 bit words and accumulator registers. The PDP-8 had 12 bit words and a single accumulator that was 12 bits wide. The PDP-10 (and derivative DEC-20) had 36 bit words and registers. Weird, but true. Don't even ask how they represented ASCII strings (:-)). We used to call those machines octal machines, as opposed to hex machines (like the IBM ones), because you could represent the contents of 12 or 18 or 36 bit words with an integral number of octal digits (4, 6, or 12). Ancient history, of course. Speaking as someone who remembers when you would enter those octal digits via the front panel of your refrigerator sized 8K word computers to boot them.