Version Number Ordering Systems
Version numbers very quickly evolve from simple integers (1, 2, ...) to rational numbers (2.08, 2.09, 2.10) and then to non-numeric "numbers" such as 4:3.4.3-2. These complex version numbers are therefore better treated as character strings. Operating systems that include package management facilities (such as all non-trivial Linux or BSD distributions) will use a distribution-specific algorithm for comparing version numbers of different software packages. For example, the ordering algorithms of Red Hat and derived distributions differ to those of the Debian-like distributions.
As an example of surprising version number ordering implementation behavior, in Debian, leading zeroes are ignored in chunks, so that 5.0005 and 5.5 are considered as equal, and 5.5<5.0006. This can confuse users; string-matching tools may fail to find a given version number; and this can cause subtle bugs in package management if the programmers use string-indexed data structures such as version-number indexed hash tables.
In order to ease sorting, some software packages will represent each component of the major.minor.release scheme with a fixed width. Perl represents its version numbers as a floating-point number, for example, Perl's 5.8.7 release can also be represented as 5.008007. This allows a theoretical version of 5.8.10 to be represented as 5.008010. Other software packages will pack each segment into a fixed bit width, for example, 5.8.7 could be represented in 24 bits: ( 5 << 16 | 8 << 8 | 7; hexadecimal: 050807; for version 12.34.56 in hexadecimal: 0C2238). The floating-point scheme will break down if any segment of the version number exceeds 1,000; a packed-binary scheme employing 8 bits apiece after 256.
Read more about this topic: Software Versioning
Famous quotes containing the words version, number, ordering and/or systems:
“It is never the thing but the version of the thing:
The fragrance of the woman not her self,
Her self in her manner not the solid block,
The day in its color not perpending time,
Time in its weather, our most sovereign lord,
The weather in words and words in sounds of sound.”
—Wallace Stevens (1879–1955)
“In the multitude of middle-aged men who go about their vocations in a daily course determined for them much in the same way as the tie of their cravats, there is always a good number who once meant to shape their own deeds and alter the world a little.”
—George Eliot [Mary Ann (or Marian)
“Make gracious attempts at sanctifying Jenny,
Supply cosmetics for the ordering of her frame,
Think of her as Leda, as a goddess,
Emptying a smile on Redkey, Indiana.”
—Allen Tate (1899–1979)
“No civilization ... would ever have been possible without a framework of stability, to provide the wherein for the flux of change. Foremost among the stabilizing factors, more enduring than customs, manners and traditions, are the legal systems that regulate our life in the world and our daily affairs with each other.”
—Hannah Arendt (1906–1975)