calibre is free and open source e-book computer software that organizes, saves and manages e-books, supporting a variety of formats. It also supports e-book syncing with a variety of popular e-book readers and will, within DRM restrictions, convert e-books between differing formats.

Kovid Goyal started developing libprs500 on October 31st 2006, when the Sony PRS-500 was introduced. The main idea was to enable the use of the PRS-500 on Linux. Kovid Goyal, with support from the MobileRead forum, reverse-engineered the proprietary file format LRF. During 2008, the name was changed to calibre.

e-books can be imported into the calibre library, either by adding files manually, or by syncing an e-book reading device.

calibre supports all the currently commercially relevant file formats and reading devices. Most of these e-book formats can be edited, for example, by changing the font or the font size and by adding a auto-generated table of contents. As well as editing, printing is also supported.

calibre helps to organize the personal e-book library by allowing the user to sort and group e-books by metadata fields. Metadata can be pulled from many different sources (ISBNdb.com, Google Books, Amazon, LibraryThing). Full-text search, including the whole library, is possible.

In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it.

In a rifled barrel, the distance is measured between opposing lands or grooves; groove measurements are common in cartridge designations originating in the United States, while land measurements are more common elsewhere. It is important to performance that a bullet should closely match the groove diameter of a barrel to ensure a good seal. When the barrel diameter is given in inches, the abbreviation "cal" is used in place of "inches." For example, a small bore rifle with a diameter of 0.22 inch is a .22 cal; however, the decimal point is generally dropped when spoken, making it "twenty-two caliber" or a "two-two caliber". Calibers of firearms can be referred to in millimeters, as in a "caliber of eighty-eight millimeters" (88 mm) or "a hundred and five-millimeter caliber gun" (often abbreviated as "105 mm gun").

While modern cartridges and cartridge firearms are generally referred to by the cartridge name, they are still lumped together based on bore diameter. For example, a firearm might be described as a ".30 caliber rifle", which could be any of a wide range of cartridges using a roughly .30 inch projectile; or a ".22 rimfire", referring to any rimfire cartridge using a .22 caliber projectile.

Computer software, or just software, is a collection of computer programs and related data that provides the instructions for telling a computer what to do and how to do it. Software refers to one or more computer programs and data held in the storage of the computer for some purposes. In other words, software is a set of programs, procedures, algorithms and its documentation concerned with the operation of a data processing system. Program software performs the function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software. The term was coined to contrast to the old term hardware (meaning physical devices). In contrast to hardware, software "cannot be touched". Software is also sometimes used in a more narrow sense, meaning application software only. Sometimes the term includes data that has not traditionally been associated with computers, such as film, tapes, and records.