Understanding History of electronic digital systems

Although,  digital  signals  are  generally  associated  with  the  binary electronic  digital  systems  used  in  modern  electronics  and  computing, digital systems are actually ancient, and need not be binary or electronic. Below are some examples of digital signals that  are neither binary nor electronic. Written text in books (due to the limited character set and the use of discrete symbols - the alphabet in most cases) An abacus  was created sometime between 1000 BC  and  500 BC; it later became a form of calculation
frequency. Nowadays it can be used as a very advanced, yet, basic digital calculator that uses beads on rows to represent numbers. Beads only have meaning in discrete up and down states, not in analog in-between states. A  beacon  is  perhaps  the  simplest  non-electronic  digital  signal, with just two states (on and off). In particular,  smoke signals  are one  of  the  oldest  examples  of  a  digital  signal,  where  an  analog "carrier" (smoke) is modulated with a blanket to generate a digital signal (puffs) that conveys information. Morse code  uses six digital states—dot, dash, intra-character gap (between  each  dot  or  dash),  short  gap  (between  each  letter), medium  gap  (between  words),  and  long  gap  (between
sentences)—to  send  messages  via  a  variety  of  potential  carriers such  as  electricity  or  light,  for  example  using  an  electrical telegraph or a flashing light. The  Braille  system  was  the  first  binary  format  for  character encoding, using a six-bit code rendered as dot patterns. Flag semaphore  uses rods or flags held in particular positions to send  messages  to  the  receiver  watching  them  some  distance away. International maritime signal flags  have distinctive markings that represent letters of the alphabet to allow ships to send messages to each other. More recently invented, a  modem  modulates an analog "carrier"
signal  (such  as  sound)  to  encode  binary  electrical  digital information, as a series of binary digital sound pulses. A slightly earlier, surprisingly reliable  version of the same concept was to bundle  a  sequence  of  audio  digital  "signal"  and  "no  signal" information (i.e. "sound" and "silence") on  magnetic cassette tape
for use with early home computers.