Vietnamese Quoted-Readable

Vietnamese Quoted-Readable (usually abbreviated VIQR), also known as Vietnet, is a convention devised in 1992 for writing Vietnamese using ASCII characters encoded in only seven bits, making it possible for computing and communication systems of the time to support Vietnamese text. Because the Vietnamese alphabet contains a complex system of diacritical marks, VIQR requires the user to type in a base letter, followed by one or two characters that represent the diacritical marks.

Source: Wikipedia — Vietnamese Quoted-Readable (CC BY-SA 4.0)