Difference between pages "Zip" and "Unix"

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'''Unix''' or '''UNIX''' is a general-purpose multi-user [[operating system]] developed mostly by [[Ken Thompson]] and [[Dennis Ritchie]] during 1969 at [[Bell Labs]]. About one year later during the early 1970s UNIX was unveiled to the general public. The original goal as it is today was to create a stable, secure, and powerful operating system that is portable to many different hardware platforms.
  
.ZIP is an archive file format that supports lossless data compression.
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Today UNIX has evolved into three main categories which all flavors of UNIX derive from: [[BSD]] (Berkley Software Distribution), [[System V]] Release 4, and hybrid. Some of the most poplar flavors of UNIX are: [[IBM]]’s [[AIX]], [[Sun Microsystems]]' [[Solaris]], [[SGI]]’s [[IRIX]], [[Linux]], [[OpenBSD]], and [[FreeBSD]].
 
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<b>TODO</b> describe ZIP64
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== File format ==
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+
{| class="wikitable"
+
! align="left"| Characteristics
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! Description
+
|-
+
| Byte order
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| little-endian
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|-
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| Date and time values
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|
+
|-
+
| Character strings
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|
+
|}
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=== Central directory (archived) file header ===
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The central directory (archived) file header is variable of size and consists of:
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{| class="wikitable"
+
! align="left"| Offset
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! Size
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! Value
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! Description
+
|-
+
| 0
+
| 4
+
| "PK\x01\x02"
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| Signature
+
|-
+
| 4
+
| 2
+
|
+
| Creator version
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|-
+
| 6
+
| 2
+
|
+
| Extractor version
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|-
+
| 8
+
| 2
+
|
+
| Flags
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|-
+
| 10
+
| 2
+
|
+
| Last modification time
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|-
+
| 12
+
| 2
+
|
+
| Last modification date
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|-
+
| 14
+
| 4
+
|
+
| Checksum (CRC-32)
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|-
+
| 18
+
| 4
+
|
+
| Uncompressed data size
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|-
+
| 22
+
| 4
+
|
+
| Compressed data size
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|-
+
| 26
+
| 2
+
|
+
| File name size
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|-
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| 28
+
| 2
+
|
+
| Extra field size
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|-
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| 30
+
| 2
+
|
+
| File comment size
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|-
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| 32
+
| 2
+
|
+
| Segment file (disk) number
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|-
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| 34
+
| 2
+
|
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| internal file attributes
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|-
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| 36
+
| 4
+
|
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| external file attributes
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|-
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| 40
+
| 4
+
|
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| local header offset <br> The offset of the local header relative to the start of the segment file it is stored in.
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|-
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| 44
+
| ...
+
|
+
| File name
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|-
+
| ...
+
| ...
+
|
+
| Extra field
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|-
+
| ...
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| ...
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|
+
| File comment
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|}
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==== Creator version ====
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The creator (or version made by) is 2 bytes of size and consists of:
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{| class="wikitable"
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! align="left"| Offset
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! Size
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! Value
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! Description
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|-
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| 0
+
| 1
+
|
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| ZIP format version <br> The value is stored as: ( major number x 10 ) + minor number
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|-
+
| 1
+
| 1
+
|
+
| Creator system indicator
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|}
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===== Creator system indicator =====
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{| class="wikitable"
+
! align="left"| Value
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! Identifier
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! Description
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|-
+
| 0
+
|
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| MS-DOS and OS/2 (FAT / VFAT / FAT32 file systems) or compatible systems
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|-
+
| 1
+
|
+
| Amiga
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|-
+
| 2
+
|
+
| OpenVMS
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|-
+
| 3
+
|
+
| UNIX
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|-
+
| 4
+
|
+
| VM/CMS
+
|-
+
| 5
+
|
+
| Atari ST
+
|-
+
| 6
+
|
+
| OS/2 H.P.F.S.
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|-
+
| 7
+
|
+
| Macintosh
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|-
+
| 8
+
|
+
| Z-System
+
|-
+
| 9
+
|
+
| CP/M
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|-
+
| 10
+
|
+
| Windows NTFS
+
|-
+
| 11
+
|
+
| MVS (OS/390 - Z/OS)
+
|-
+
| 12
+
|
+
| VSE
+
|-
+
| 13
+
|
+
| Acorn Risc
+
|-
+
| 14
+
|
+
| VFAT
+
|-
+
| 15
+
|
+
| alternate MVS
+
|-
+
| 16
+
|
+
| BeOS
+
|-
+
| 17
+
|
+
| Tandem
+
|-
+
| 18
+
|
+
| OS/400
+
|-
+
| 19
+
|
+
| OS X (Darwin)
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|-
+
| 20 - 255
+
|
+
| unused
+
|}
+
 
+
==== Internal file attributes ====
+
{| class="wikitable"
+
! align="left"| Value
+
! Identifier
+
! Description
+
|-
+
| 0x01
+
|
+
| If set the uncompressed data needs to be treated as text instead of binary data. <br> This flag hints end-of-line conversion for cross-platform text files but does not enforce it.
+
|-
+
| 0x02
+
|
+
| If set the file contains control fields for mainframe data transfer support.
+
|}
+
 
+
==== External file attributes ====
+
The external attributes are creator system dependent.
+
 
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The external attributes MS-DOS (0) is 4 bytes of size and consists of:
+
{| class="wikitable"
+
! align="left"| Offset
+
! Size
+
! Value
+
! Description
+
|-
+
| 0
+
| 1
+
|
+
| FAT (MS-DOS) file attributes.
+
|-
+
| 1
+
| 3
+
|
+
| Unknown
+
|}
+
 
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The external attributes UNIX (3) is 4 bytes of size and consists of:
+
{| class="wikitable"
+
! align="left"| Offset
+
! Size
+
! Value
+
! Description
+
|-
+
| 0
+
| 1
+
|
+
| FAT (MS-DOS) file attributes.
+
|-
+
| 1
+
| 1
+
|
+
| Unknown
+
|-
+
| 2
+
| 12 bits
+
|
+
| The UNIX mode (or permission).
+
|-
+
| 3.4
+
| 4 bits
+
|
+
| Unknown
+
|}
+
  
 
== External Links ==
 
== External Links ==
  
* [http://www.pkware.com/documents/casestudies/APPNOTE.TXT .ZIP File Format Specification], PKWARE Inc., September 1, 2012
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* [http://upload.wikimedia.org/wikipedia/commons/5/50/Unix_history-simple.png Wikipedia: Time Line of UNIX]
* [http://en.wikipedia.org/wiki/Zip_(file_format) Wikipedia: Zip (file format)]
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* [http://blog.eukhost.com/2006/11/30/linux-flavors: Unix Flavours]
 +
* [http://www.unix.org/version4/ The Single UNIX Specification, Version 4]
  
[[Category:File Formats]]
+
=== File permissions ===
 +
* [http://content.hccfl.edu/pollock/aunix1/filepermissions.htm Unix File and Directory Permissions and Modes], by Wayne Pollock, 2001

Revision as of 02:44, 1 December 2013

Unix or UNIX is a general-purpose multi-user operating system developed mostly by Ken Thompson and Dennis Ritchie during 1969 at Bell Labs. About one year later during the early 1970s UNIX was unveiled to the general public. The original goal as it is today was to create a stable, secure, and powerful operating system that is portable to many different hardware platforms.

Today UNIX has evolved into three main categories which all flavors of UNIX derive from: BSD (Berkley Software Distribution), System V Release 4, and hybrid. Some of the most poplar flavors of UNIX are: IBM’s AIX, Sun Microsystems' Solaris, SGI’s IRIX, Linux, OpenBSD, and FreeBSD.

External Links

File permissions