A static dictionary is a fixed dictionary that is produced before the coding process and used at both the transmitting and receiving ends. It has the advantage of simplicity but the drawbacks of relatively lower coding efficiency and less flexibility compared to adaptive dictionary techniques. A static dictionary can be used for languages like Java and C# and stored in non-static classes, sometimes for performance optimization. Common static dictionary coding involves encoding pairs of symbols using a dictionary containing all source symbols and frequently used pairs. If a pair is in the dictionary, its index is used to encode it; otherwise, the first symbol's index and a new pair with the next symbol are encoded.

1. Prepared by- Prince Paneliya (150120116047)
Guided by-
Prof. Alpa Oza
SUBJECT-DCDR (2161603)
Static Dictionary
Gandhinagar Institute of Technology

2. Static Dictionary
 A fixed dictionary,
 Produced before the coding process
 Used at both the transmitting and receiving ends
 It is possible when the knowledge about the source alphabet and the
related strings of symbols, also known as phrases is sufficient.
 Merit of the static approach: its simplicity.
 Its drawbacks lie on
 Relatively lower coding efficiency
 Less flexibility compared with adaptive dictionary techniques

3. Continue
 A static dictionary can be use to the java , C sharp
etc.
 The static Dictionary is encapsulated in a static
class.
 A static Dictionary can be stored in a non-static
class. In this case, it will still be tied to the type, not
the instance. Sometimes, using a static Dictionary is
a good performance optimization.

4. Continue
 diagram coding is the common form of static dictionary coding.
 The dictionary contains:
 all source symbols and
 some frequently used pairs of symbols.
 In encoding, two symbols are checked at once to see if they are in the
dictionary.
 If so, they are replaced by the index of the two symbols in the dictionary,
and the next pair of symbols is encoded in the next step.
 If not, then the index of the first symbol is used to encode the first
symbol. The second symbol is combined with the third symbol to form a
new pair, which is encoded in the next step.

5. Example
● Suppose we are having the source:
A = {u,v,w,x,y,z}

6. ● Suppose we wish to encode the sequence
uvzuxuyuvzu
● The output string for the given input sequence is
101100110111101100000
● Refer fig.

7. Advantages
● A simple and fast coding technique.
● It is a predefined dictionary.
● It does not change during execution.
● It used reference for comparison of decompressor.
● Adds extra overhead to the encoding procedure.
● Size id of fixed type.
● Dictionary does not grow during the compression of decompression.
● Problem occurs in passing dictionary from encoder to decoder.
● This problem can be issues in small file as it act as added overhead for
the very same.

8. Static Dictionary
● It contains new collection of
unmatched string.
● It is permanent.
● In this sometimes additions are
allowed.
● Deletion is not allowed.
Adaptive dictionary
● It holds the stream previously
found in input stream.
● It is adaptive keep changing.
● Additions of the new string are
allowed.
● Deletion is allowed.

9. References
● people.cs.nctu.edu.tw/~cjtsai/courses/imc/classnotes
/imc14_05_Dictionary_Codes.pdf
● users.ece.utexas.edu/~ryerraballi/MSB/pdfs/M2L3.p
df
● ieeexplore.ieee.org/document/6633967
● https://en.wikibooks.org/wiki/Data_Compression/Di
ctionary_compression

10. Thank You