Image source: http://d3thflcq1yqzn0.cloudfront.net/009928588_prevstill.jpeg
The number system was the earliest code developed by man. Once it went through about five stages of development, it became powerful enough to represent real-life phenomena in terms of mathematics. Such a representation can be called codes because the process of representation is not straight like a symbol, and the process of understanding that representation requires considerable decoding.
The number system became a powerful way of coding numbers after about five stages of development, but technology soon helped coding to be applied to higher levels of thought. The earliest use of technology was in the form of Abacus. Several millennia after that came Slide Rules that took mathematical coding through a very large leap. Here numbers are converted to logarithms (which can be called a type of numerical code) which was then converted to proportional length. Once numbers were coded into logs and then logs into length, representing very large numbers into lengths, then solving large computations became easy. Coding took advantage of technology to make age-old problems easy to handle.
Coding took another leap when analog counting machines based mostly on interlocking teeth were invented. Thanks to Charles Babbage, very advanced computing machines were conceived and some were made. These were based on systems of wheels and gears. This was another level to which technology helped numerical coding. The next stage was small relay-based computers that paved the way for binary-coded decimal computations. Meanwhile the arrival of Analog Computers did for computation what the Slide Rule had done for engineers. However, all of this was only preparing the ground for ENIAC, the first machine that opened the way for modern computers.
While a computer looks like a simple computing-machines, the actual working is heavily dependent upon coding. At a very early stage they realized that computers cannot "represent" numbers the way symbols like 3, 5, or 7 represent on paper. Thus binary numbers, which have only two digits were the stuff of computers, and continue to be so. Since on/off positive-pulse/negative-pulse type of information is the only thing where there is mathematical certainty of what the signal is, in spite of random corruption, the decimal system that we are used to was coded into binary. Then the 0 and 1 (the only numerals in binary) were coded into the two allowed states of vacuum tube valves or (eventually) transistors.
In effect, the two clear-cut states of a signal (say, on/off) were used to represent (code for) binary numbers, which were used to represent decimal numbers, and so on. Thus eventually, the processing of digital electronic signals was used to represent decimal numbers, through several levels of coding. This was the ultimate in technological help in coding for numbers. This in turn gave rise to the next stage of coding, which has now brought computers into everyday life.
