bit 10: representing digital information


bit 10: representing digital information

converting analog and digital signals and how computers use binary numbers to interpret information

Computers are digital processors which represent information in discrete chunks and discrete values, or numbers. These numbers are represented in a unit called a bit which is a binary digit, or a number which is either 0 or 1. The traditional decimal system is base-10 using numbers 0-9, but binary numbers are base-2, so only 0 and 1 are used before requiring another decimal place. Groups of bits represent parts of a larger whole - numbers, letters, sounds, images, movies, etc. The reason there are only two values is because a bit is a digital signal, meaning it has only two discrete values. In order to understand how bits function using binary digits, we must first analyze the difference between analog and digital signals.

analog vs. digital signals

Many signals we encounter in the real world are analog, meaning the signal varies smoothly and consistently in proportion to the amount of change in the value. There are an unlimited amount of variables to one signal which can be represented. For example, turning the steering wheel in a car is an analog signal because the car will only turn in proportion to how much you turn the wheel.

Digital systems, however, deal strictly with discrete values, meaning there are only a fixed number of possible values or outcomes. This is much like flipping a switch - it is either on or off, there is no in between. To compare analog and digital signals, think of the speedometer in a car. If your car has an analog speedometer using a needle, it will move slightly depending on your change in speed, but it can represent any value between 0 to 160 mph. A digital speedometer represents the value to the nearest mph, and would simply display 66 for any value from 65.5 to 66.5 mph. This is because the signal can only be interpreted two ways - it is either 66 mph or it is another number.

signal conversion

Analog data from the external world such as sound, temperature, and movement is converted as soon as possible to a digital signal on the input side, and then converted back to an analog signal as late as possible on the output side. This is because digital data is easier for computers to work with, since it does not have to interpret the value. Let’s look at this process through the conversion of images to digital form:

An analog camera uses light signals and creates an image by exposing a light-sensitive area of plastic film to the light from the object being photographed. Different areas of the photos receive different amounts of light respectively, which affects the amount of dye used when the film is being developed. The amount of light has no fixed number of variables, it only depends on how exposed a particular aspect of the image is.

In comparison, a digital camera lens focuses the image onto a rectangular array of tiny light-sensitive detectors which lie between red, green, and blue filters. Each detector stores a certain amount of electric charge proportional to the amount of light exposed to it, which is then converted into a numeric value. The digital image becomes a sequence of these numeric values, representing varying light intensities. This is also why digital art is created in RGB format, because the screen display uses tiny pixels of each color to create corresponding color values.

RGB pixels

When converting an analog file to a digital image, the computer uses combinations of red, green, and blue color values to create the color for a single pixel. Each value can range from 0 which is black, to 255, which is the brightest form of any RGB color.

This video by the creator of Instagram further describes how RGB pixels are used to create a color resolution on screens:

More info on the digital world coming soon….