PCM and RAW
The PCM is simply a result of uncompressed audio data, which is usually stored as .WAV on Windows or .Aiff on Mac OS. WAV and AIFF are flexible audio file formats designed to store more or less any combination of sampling rates or bitrates.
These are the appropriate file formats for storage and execution of original recordings.
RAW (Real Audio Wrapper) is an audio format used to represent data in the pulse coded without header or metadata modulation. The RAW file is unusable without information about coding, which must be sent elsewhere.
CDA (Compact Disc Audio) is a specific Microsoft Windows format, audio CD tracks, as they appear when inserted into the CD-ROM drive. The sampling used for the CD technique is pulse coded (PCM for Pulse Coded Modulation). The file suffix is created .Cda.
Audio codec with lossless compression
The lossless audio compression like any other computer file identifies redundancies in audio files. With reference to the information theory of Claude Shannon, it is described as entropy coding.
Lossless compression entails using an algorithm such that we can always recover the original data.
This file contains no useful information neither discernible frequency or level variation or rhythm, all the elements that make the difference between the signal and noise are based on repetition.
Typically, lossless compression is used to divide the file size by two or three. It is relatively little used, because the gain is very low compared to those allowed by the lossy compression (which is a big handicap for the exchange of files), and entails time-consuming calculation for coding.
No standard has thus sufficiently become universally readable.
FLAC (Free Lossless Audio Codec) format is an open format for lossless audio compression. Maintained by the Xiph.org foundation, it is treasured to maintain quality of the original sound files in alternative formats MP3 lossy compression category.
ALAC (Apple Lossless Audio Codec) format is a lossless coding created in 2004 by Apple.