File compressor
US4672539A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 17, 1985 |
| Grant date | Jun 9, 1987 |
| Priority date | — |
| Expiry date | Apr 17, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M7/4006
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An adaptive method of file compression is based on the recognition that language can be thought of as a stream of alternating words and separators. Empty dictionaries are created for the words and separators. For each event in the data stream, a determination is made whether the word is in the dictionary for words compiled from the previously encountered words or whether the word is a new word. If the event is a separator, a similar determination is made using the dictionary for separators. If the event is a new word or a new separator, the event is encoded with a predetermined new word or new separator symbol followed by encoding the characters of the word or separator. A count is maintained of all word events and a count is maintained of all separator events as those events are encoded. In addition, individual counts for each occurence of a word and each occurence of a separator are maintained. The ratio of the number of times a word has been encountered to the total number of words encountered is used to estimate the probability of the word. Similarly, the ratio of the number of times a separator has been encountered is used to estimate the probability of the separator. These pr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.