. . 2.
{A; B} N (N ). :
- ;
- ;
- 1- .
2, 3 4 . .
|
2
7.1 .
7.2 .
7.3 .
7.4 . 5.2...5.4 (, ).
7.5 , .
7.6 , , 100- .
2.3
LZW
1.1 LZW.
1.2 LZW.
2.1 , , , . ai bi, n :
(1)
M A; , M 2.
. -2, ASCII . , .. , , n.
, :
(2)
: H (A) , ..;
.
.
(2) , , . , , . , .. , , .
2.2 , , ( ) . :
|
|
- , ;
- , ;
- , , .
-. , -: LZ77, LZ78, LZW . , , .. , .
-: RAR, ZIP . , .. . LZ77 . . .
V.42bis, V.42 . LZW LZ78, . . , V.42 , , , , .
2.3 LZ77, LZ78 LZW. , .., , , . ( ) , , , , . , , .
2.4 LZW. LZW :
- , ;
- ;
- , .
, , .. . , , ASCII. , , 256 , . , 0 255. . 1.
1
"NULL" | 00 0000 0000 | |
... | ... | ... |
"" | 00 0100 0001 | |
"" | 00 0100 0010 | |
"" | 00 0100 0011 | |
"D" | 00 0100 0100 | |
... | ... | ... |
"ٱ" | 00 1111 1111 | |
... | ... | ... |
. 1 , , . , , .. . . 1 1024 . , :
|
|
(3)
.
:
1) , , , , ;
2) , , ;
3) ( ) , .
. 2 : "ABABCABCABCA".
112 :
1. A, "A", . , . "A".
2. B, "AB", . "AB" 256, , .. "A" 65. "B".
3. , "", . "" 257, , .. "B" 66. "A".
4. , "AB", . , . "AB".
5. C, "ABC", . "ABC" 258, , .. "AB" 256. "".
2 LZW
? | |||||||
A | "A" | - | - | - | "A" | ||
B | "AB" | "AB" | "B" | ||||
"" | "" | "A" | |||||
B | "AB" | - | - | - | "AB" | ||
C | "ABC" | "ABC" | "C" | ||||
A | "CA" | "CA" | "A" | ||||
B | "AB" | - | - | - | "AB" | ||
C | "ABC" | - | - | - | "ABC" | ||
A | "ABCA" | "ABCA" | "A" | ||||
B | "AB" | - | - | - | "AB" | ||
C | "ABC" | - | - | - | "ABC" | ||
A | "ABCA" | - | - | "" |
6. , "CA", . "CA" 259, , .. "" 67. "".
7. , "A", . , . "A".
|
|
8. , "A", . , . "A".
9. , "CA", . "CA" 260, , .. "" 258. "".
10. , "A", . , . "A".
11. , "A", . , . "A".
12. , "A", . . , , .. "A" 260.
, "ABABCABCABCA" : 65 66 256 67 258 260.
2.5 , LZW, :
- h;
- ;
- , .
, , .
:
, (4)
: N , ;
N , .
2.6 , "ABABCABCABCA", : . , : . , "ABABCABCABCA" 1,6 .
"ABA". : 65 66 65. , : . , , , .
. , , , , , .
2.7 LZW . LZW, , , , .
, , . , , .
LZ78 . . , . .
|
|
. , M , , .. . , V.42bis , .
. . , , , .. . , , . , , .
2.8 , . , , . , NC. .., , NC, , , . V.42bis , 6 250 .
2.9 LZW , . :
1) , ;
2) ;
3) ;
4) , .
LZW "65 66 256 67 258 260" . 3. , , . : .
3 LZW
? | ||||||
"" | "" | - | - | "" | ||
"" | "" | "" | "" | |||
"" | "" | "" | "" | |||
"" | "" | "" | "" | |||
"" | "" | "" | "" | |||
"" | "" | "" | "" |
2.10 , , . , "193" "65", , . , V.42bis, . , . , "65 66 256 66 258 260". "". , , .. . , .
3.1 ?
3.2 ?
3.3 .
3.4 ?
3.5 ?
3.6 .
3.7 LZW.
3.8 LZW.
4.1 " ". [2, . 16...27; 5, . 876...887].
|
|
4.2 LZW , . 4. . 2.
4.3 . 4.2 . . 3.
4.4 .
4
AAABCD | |
DAAABC | |
CDAAAB | |
BCDAAA | |
ABCDAA | |
AABCDA |
5.1 . 2.3 LZW, , 2. , . 6. .
5.2 . . " ". , " " . " ". " ". " ". . . 4.2 . "".
, , " ". , " ". " ". . , . "".
5.3 . , . . 2, . 3. "aaaaaaaaaaaaaaaaaaaaaaaaaaaa". . 2 . 3 . , NC.
5.4 . " " " ". : N = 1000 ; = 512 ; NC = 6 . "" . , " " " Word". .
5.5 . " ". : = 512 ; NC = 6 . N: 1, 5, 10, 25, 50, 100, 200. η(N). .
5.6 . " " N = 5000 , NC = 6. M: 512, 1024, 2048, 4096. η(). .
5.7 . NC = 50 . 5.6. η(). .