Epson FX-185 User Manual - Page 153

Since computers use the binary numbering system (OS and 1s only), it is most efficient for each pin to correspond to the decimal equivalent of one bit in an &bit binary number: 1, 2, 4, 8, 16, etc. (see Figure 10-3). Figure 10-3. Pins labelled uniquely The hardware makes this the most practical labelling system. Each pin corresponds to one of the eight data lines from the computer, and each data line corresponds to one bit in a binary number. The place values in a binary number are nothing more than the series made up of powers of two. Figure 10-4 shows how you use a decimal sum--74-to fire a particular pattern of pins. If you try adding several sets of pins together, you'll see that with this system you get no duplicates. The number 6 represents pins 2 and 4 (since 2 + 4 = 6) and there is no other way to get 6 by adding powers of two. This means that any combination of the eight pins adds up to a unique decimal number which falls within the range 0 to 255. 136