Have you noticed the tiny coloured stripes on the resistors in the interiors of electronic gadgets? These coloured stripes known as the Electronic Color Code indicate the resistor’s resistance value. To a layman, the band system might seem strange, but to a serious hobbyist or to a professional in electricity and electronics the bands help to know the values of the resistors easily.
The colour code system was developed in the 1920s by the Radio Manufacturers Association (an organization now known as the Electronic Industries Alliance). This system of colour-coded bands has prevailed for the better part of a century now and will likely continue to do so.
In the above standard 4-band resistor the colour and order of the bands serve to indicate the significant figures of the resistor’s value (the first two bands), as well as the decimal multiplier (the third band), and the tolerance of the resistor (the fourth band).
In the above standard 5-band resistor the first three bands show the resistor’s value, the fourth band indicates the decimal multiplier and the fifth band the tolerance of the resistor.
Now with the advent of tiny surface-mount resistors that are often hardly bigger than a grain of rice, has led to an increase in alpha-numeric coding in lieu of the banding method.