IndiceBRTableOfContents(2) |
What is a package?
Software is a very broad term, and is generally taken to mean a program which you can run on your computer. However, such programs often need other resources to work. When you install software, thousands of files may be required just to let the program start! When you think that they all have to be put in exactly the right location, and some of those files may need to be changed depending on what type of computer you have, it can all get very complicated. Luckily, Ubuntu can look after this complexity.
Ubuntu uses packages to store everything that a particular program needs to run. A 'package', then, is essentially a collection of files bundled into a single file, which can be handled much more easily. As well as the files required for the program to run, there will be special files called installation scripts, which copy the files to where they are needed (amongst other things).
Source or Binary?
Normally, when someone makes a package for a program, they put all of the source code for the program into that package. Source code is written by programmers and is essentially a list of instructions to a computer which humans are able to read and write. Computers can only understand this code if it is interpreted for them into a form that they can use directly. One such way of interpreting source code for a computer is by translating or compiling it into binary, which computers can understand.
So why don't the people who make the package (called packagers) just convert it into binary from the start? Well, different computers use different types of binary, so if you make a binary package for one type (like an Intel PC), it won't work on another (like an Apple Macintosh).
Source packages are simply packages which just include source code, and can generally be used on any type of machine if the code is compiled in the right way. BR Binary packages are ones which have been made specifically for one type of computer, or architecture. Ubuntu supports the x86 (i386 or i686), AMD64 and PPC architectures. The correct binary packages will be used automatically, so you don't have to worry about picking the right ones. To find out which one you are using, open Applications → Accessories → Terminal, type arch then hit the enter key.
Package Dependencies
Programs often use some of the same files as each other. Rather than putting these files into each package, a separate package can be installed to provide them for all of the programs that need them. So, to install a program which needs one of these files, the package containing those files must also be installed. When a package depends on another in this way, it is known as a package dependency. By specifying dependencies, packages can be made smaller and simpler, and duplicates of files and programs are mostly removed.
When you install a program, its dependencies must be installed at the same time. Usually, most of the required dependencies will already be installed, but a few extras may be needed, too. So, when you install a package, don't be surprised if several other packages are installed too - these are just dependencies which are needed for your chosen package to function properly.
