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diff --git a/sag-0.6.1-www/Invisible/sag-0.6/node32.html b/sag-0.6.1-www/Invisible/sag-0.6/node32.html new file mode 100644 index 0000000..906fe80 --- /dev/null +++ b/sag-0.6.1-www/Invisible/sag-0.6/node32.html @@ -0,0 +1,81 @@ +<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> +<!--Converted with LaTeX2HTML 96.1-h (September 30, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds --> +<HTML> +<HEAD> +<TITLE>CD-ROM's</TITLE> +<META NAME="description" CONTENT="CD-ROM's"> +<META NAME="keywords" CONTENT="sag"> +<META NAME="resource-type" CONTENT="document"> +<META NAME="distribution" CONTENT="global"> +<LINK REL=STYLESHEET HREF="sag.css"> +</HEAD> +<BODY LANG="EN" > + <A NAME="tex2html716" HREF="node33.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html714" HREF="node28.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html708" HREF="node31.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html718" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html719" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html717" HREF="node33.html">Tapes</A> +<B>Up:</B> <A NAME="tex2html715" HREF="node28.html">Using Disks and Other </A> +<B> Previous:</B> <A NAME="tex2html709" HREF="node31.html">Floppies</A> +<BR> <P> +<H1><A NAME="SECTION00540000000000000000">CD-ROM's</A></H1> +<P> + A CD-ROM drive uses an optically read, plastic coated disk. + The information is recorded on the surface of the + disk<A NAME="tex2html14" HREF="footnode.html#1067"><IMG ALIGN=BOTTOM ALT="gif" SRC="./foot_motif.gif"></A> in small `holes' + aligned along a spiral from the center to the edge. The + drive directs a laser beam along the spiral to read the disk. + When the laser hits a hole, the laser is reflected in one way; + when it hits smooth surface, it is reflected in another way. + This makes it easy to code bits, and therefore information. + The rest is easy, mere mechanics. +<P> + CD-ROM drives are slow compared to hard disks. Whereas a + typical hard disk will have an average seek time less than + 15 milliseconds, a fast CD-ROM drive can use tenths of a second + for seeks. The actual data transfer rate is fairly high at + hundreds of kilobytes per second. The slowness means that + CD-ROM drives are not as pleasant to use instead of hard disks + (some Linux distributions provide `live' filesystems on CD-ROM's, + making it unnecessary to copy the files to the hard disk, making + installation easier and saving a lot of hard disk space), although + it is still possible. For installing new software, CD-ROM's are + very good, since it maximum speed is not essential during + installation. +<P> + There are several ways to arrange data on a CD-ROM. The most + popular one is specified by the international standard ISO 9660. + This standard specifies a very minimal filesystem, which is + even more crude than the one MS-DOS uses. On the other hand, + it is so minimal that every operating system should be able to + map it to its native system. +<P> + For normal UNIX use, the ISO 9660 filesystem is not usable, so + an extension to the standard has been developed, called + the Rock Ridge extension. Rock Ridge allows longer filenames, + symbolic links, and a lot of other goodies, making a CD-ROM + look more or less like any contemporary UNIX filesystem. + Even better, a Rock Ridge filesystem is still a valid ISO 9660 + filesystem, making it usable by non-UNIX systems as well. + Linux supports both ISO 9660 and the Rock Ridge extensions; + the extensions are recognized and used automatically. +<P> + The filesystem is only half the battle, however. Most CD-ROM's + contain data that requires a special program to access, and + most of these programs do not run under Linux (except, possibly, + under dosemu, the Linux MS-DOS emulator). +<P> + A CD-ROM drive is accessed via the corresponding device file. + There are several ways to connect a CD-ROM drive to the computer: + via SCSI, via a sound card, or via EIDE. The hardware hacking + needed to do this is outside the scope of this book, but the + type of connection decides the device file. See [<A HREF="node113.html#device-list">Anv</A>] + for enlightment. +<P> +<HR><A NAME="tex2html716" HREF="node33.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html714" HREF="node28.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html708" HREF="node31.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html718" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html719" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html717" HREF="node33.html">Tapes</A> +<B>Up:</B> <A NAME="tex2html715" HREF="node28.html">Using Disks and Other </A> +<B> Previous:</B> <A NAME="tex2html709" HREF="node31.html">Floppies</A> +<P><ADDRESS> +<I>Lars Wirzenius <BR> +Sat Nov 15 02:32:11 EET 1997</I> +</ADDRESS> +</BODY> +</HTML> |