Common form of transferring analog information into digital signals by representing analog waveforms with a stream of digital bits forming words that relate the amplitude of a signal at a certain point (the sample). The word length used, the number of bits used to represent the amplitude of a sample (known as quantisation), is a determinant in the quality of reproduction along with the sampling rate (the number of samples taken per second). he word length used for standard CDs is 16 bits meaning that each amplitude is represented by a string of 16 ones and zeroes. Higher quality formats use 20 bit and 24 bit word lengths. A 20 bit word breaks up the height into 1,048,576 pieces, about 16 times more resolution that a 16 bit word (with 65,553 pieces). A 24-bit word breaks the amplitude up into 16,777,216 pieces, about 256 times the information of a 16-bit word. he word size in bits is similar to the measurements on a ruler. A 16-bit signal may only use inches to measure a line (resulting in some error when the line length is not exactly one inch or a multiple of one inch). A 20-bit signal may use half-inch markings, and a 24-bit word may use one-sixteenth inch markings. Of course, the scale of the example is incorrect, but the concept is the same (if a 16 bit word used one inch markings, a 20 bit word would use about one sixteenth of an inch markings and a 24 bit word would use one two-hundred fifty-sixth of an inch markings). The more markings used to measure something, the closer you can get to the actual measure. he digital words stream out in a series of ones and zeroes under pulse code modulation. The digital-to-analog converter is set to the corresponding sampling rate (44.1 kHz for a standard CD representing how many samples are taken each second) and word length (16 bits for standard CDs). This generates 44,100 samples for a CD with each sample containing 16 bits resulting in 705,600 bits of information passing by each second. he digital-to-analog converter uses a clock tuned to the proper frequency to read words 44,100 times per second. The DAC knows the proper length of the words (16 bits in this case for CD), and so it can look for sixteen bits of information as the CD spins by. The ones and zeroes are denoted by the transition from a pit to a land or from a land to a pit (a pit being an indentation and a land being the space between pits). he words give the height of the signal’s amplitude at each sample. The heights are all added together as the samples pass by to recreate the signal. The stair-step digital signal is smoothed into an analog wave that closely resembles the original signal. The more bits used and the higher the sampling frequency used, the closer the decoded signal coincides with the original analog signal prior to being digitally encoded. Pulse code modulation is common and found in almost all digital audio.