A Live CD is a CD Rom that is bootable, i.e. that can start up a computer by loading into the memory of the computer a basic operating system. Here is the Wikipedia’s definition of a Live CD :
A LiveCD is an operating system (usually containing other software as well) stored on a bootable CD-ROM or DVD-ROM that can be executed from it, without installation on a hard drive. The system returns to its previous OS when the LiveCD is ejected and the computer is rebooted. It does this by placing the files which typically would be stored on a hard drive, onto a ram disk. This however does cut down on the RAM available to applications, reducing performance somewhat.
You can read more about Live CD on Wikipedia.
Live CDs have been particularly used to allow users to boot a computer with a Linux operating system, along with a set of applications, without touching the hard disk and the existing operating system. This is most practical to test Linux and hardware recognition, as well as accessing to information on the hard disk when the original operating system is out of order. If the computer has enough RAM (at least 128 MB), it can be used with a Linux Live CD, even in the case of a hard disk crash/failure.
The most famous Live CD may be Knoppix, so-called from his author, a German informatician whose name is Klaus Knopper. Knoppix is a Debian-based live CD of which the first version (3.1) has been launched on 19th January 2003. The latest version is now 4.0 and has been handed out on the 22nd of June, 2005. You can read more about Knoppix on the Wikipedia here.
You can lean more about live CDs at http://www.livecdnews.com/ and http://www.livedistro.org/.
Nếu bạn muốn thử một Linux Live CD (sẽ không ảnh hưởng gì hết đến đĩa cứng và hệ điều hành đang dùng của máy tính), bạn có thể liên hệ với tôi (ông Vũ Đỗ Quỳnh, CAI-AUF, inside IFI, Nhà D, Ngõ 42 Tạ Quang Bửu (Quận Hai Bà Trưng), Hanoi - Tel: 868.48.85 ; e-mail : vu.do.quynh (at) auf.org) để sao chép một bản CD trong danh sách dưới đây (miễn phí nếu bạn đem theo đĩa CD trắng hoặc CD-RW, nếu không là 3-5 ngàn đồng tùy thuộc vào loại đĩa CD-R đang dùng). Nên gọi điện thoại trước khi đến !
If you are interested in trying Linux, or if you are in need of a Live CD for your own purpose, you may contact M. Quynh VU DO, at the Centre d’accès à l’information (CAI-AUF, inside IFI, Nhà D, Ngõ 42 Tạ Quang Bửu, Hanoi - Tel: 868.48.85 ) to obtain a copy (free if you bring your own blank CD-R or CD-RW, otherwise at the cost of a blank CD-R, between 3,000 and 5,000 Vietnam dongs, depending on the type of supply).
Please take RV (or phone first) if you intend to get several copies, as burning one CD takes some time (around 15 mn). Anyway calling before going to the CAI-AUF is a good idea because I may be absent or on leave, occasionally.