WAV
Microsoft and IBM's 1991 audio file format — in practice a thin envelope around raw PCM, which is exactly why every program can read it.
WAV arrived with the multimedia extensions to Windows 3.x and is built on RIFF, a little-endian take on Electronic Arts' IFF. A file is a series of chunks: fmt describes channels, sample rate and bit depth, data holds the audio. The format can technically carry compressed audio, but nearly always it's uncompressed PCM, which makes it dull, large and almost impossible to misinterpret.
The size field is 32 bits, so a WAV file runs out at 4 GB — about six and a half hours of 48 kHz/24-bit stereo, and a good deal less for a multitrack recording. Broadcast and film answered with Broadcast Wave (an extra chunk for timecode and metadata) and RF64 for larger files. Apple's counterpart is AIFF.