front panel switches DEC PDP-8 TI 980 1960’s The internal architecture of the machine is exposed in the controls. You can see that the PDP-8 is an octal computer, with its switches in three-bit configurations (it takes three bits to count from 0 to 7, for a total of 8 numbers. Base 8. Octal. Get it?). The TI 980 is a hexadecimal machine, with switches in groups of four. Using the switches, you program the machine one word at a time (a word being, say, two hexadecimal bytes for the TI).