(1) The directory tree cannot exceed 8 levels.
(2) Non-long file name: the file name (including its extension) must be less than 30 characters. However, for its use in MS-DOS, it has more restrictions: the file name is 8 characters at most and the extension is 3 characters at most.
(3) There is no extension in the directory name.
(4) Only capital letters are allowed.
(5) Special characters such as% or @ are not allowed.
CD burning software will help you create ISO9660 image files before formally transferring data to CD burner for recording. It is easy to use and helps to eliminate recording errors during operation, such as underloading in the buffer. When you look at the surface of a CD or soap bubbles, or a thin layer of oil floating on still water, you usually see rainbow patterns. These three effects are caused by constructive interference and destructive interference of light on film.
Take a thin layer of oil floating on the water as an example. When white light shines on the film, most of the white light will pass through the film, but some will be reflected at the top and bottom of the film. Similarly, when you stand in front of the window of the house, you can see the reflection in the window. Most of the light goes out through the window, but some of it is reflected back to you. As shown in the figure, the light reflected by the top layer of the film travels a little shorter than that reflected by the bottom layer.
In this figure, the incident light enters from the upper left corner. Part of the light directly passes through the film (a); Part of the light is reflected at the top layer of the film (b); Another part of the light is reflected at the bottom layer of the film (c).
If the film thickness is in the optical wavelength series, interference will occur. The wavelength of violet light is about 4000 angstroms (one hundredth of a centimeter), and the wavelength of red light is about 7600 angstroms, so we are talking about extremely thin films. From how the rainbow is formed, we can know that white light is composed of all other colors.
If the thickness of the film is appropriate, the red light wave (sine wave) will be reflected into a straight line on the upper and lower layers, and the two sine waves will be combined into one, so that the brightness of the red light will be doubled. Otherwise, they may reflect out of phase and the red light will disappear.
Because the CD surface is like a mirror, the rainbow color will be much stronger. For a description of the structure of the CD, please refer to the working principle of the CD. For CDs, the angle at which the CD is placed determines the color you see-because the angle determines the distance.
Extended standard
From 65438 to 0989, Japan Sun Yudian Company developed an organic soda ash CD medium with a thin layer of gold on its surface. This new medium not only provides the same physical characteristics and capacity as the silver compact disc, but also has better reflection characteristics than the commercial copy disc. This medium can be recorded by a special device that can write information on the optical disc, and the written optical disc can be read by any optical drive in turn. A device that records information on a medium is called a CD- recorder, and the medium is called a CD-R (recordable CD). The invention of CD-R technology has brought many benefits, such as:
(1) You can make your own CD at low cost on a desktop PC;
(2) information recorded in any suitable CD format can be selected;
(3) Avoid expensive training expenses and copying facilities related to business training. Because the typical CD-R medium has a lifetime of 70- 100 years, it is an ideal choice for long-term data preservation. This is a significant improvement for magnetic media with much shorter life. CD-R technology is a breakthrough, which will introduce the next revolution of data storage technology, because in this era of information explosion, the demand for large capacity is increasing.
Extended ISO9660
ISO9660 has some restrictions, such as character setting restrictions, file name length restrictions and directory tree depth restrictions. These regulations prevent users from copying data to optical disks that can be read by different computer platforms. Therefore, some operating system vendors have extended ISO9660 in various ways.
Joliet file system is one of the extended file systems proposed and implemented by Microsoft. It is based on ISO9660( 1988) standard. If you use Joliet file system to create a CD, you can only read it under window 9x and window NT4.0 or later, but not on any other platform. Under Joliet file system, the maximum number of characters allowed for long file names is 64, and the maximum number of characters allowed for long directories is 64. However, the total characters of the file name and its full path cannot exceed 120.
Romeo is only defined as the long file name of window9x, with a maximum of 128 characters. Before storing information on an optical disc, some method must be used to compress the data. In order to unify the compression method, various manufacturers have formulated many standards so that the burned discs can be used on different machines. These standards were formulated in different years and expressed in different colors of packaging. Common specifications are as follows:
(1) little red book
It was made by Philips and Sony in 1980. This is a CD-DA optical disc standard for storing audio tracks. This specification contains only tracks of audio sectors. Because CD-ROM comes from audio CD, a large amount of information stored on CD can be measured by minutes, seconds and frames, among which:
1 =60 seconds;
1 sec =75 frames;
1 frame =2048 bytes (2 kilobytes) pattern 1 user data.
Please note that the actual space occupied by a file on a CD is usually larger than its original size due to the extra consumption of sector boundaries. The disc capacity is calculated at a single speed (150KB/ s). A CD can store 74 minutes of music or 650 MB of data, and the conversion method is 74 (minutes) * 60 (seconds) * 150(KB)=666000KB=650MB, and the recording time of two-speed music CD is 74.
The capacity of 8cm CD-R disc is between 180-220MB, and the standard capacity is 2 100 MB.
(2) Yellow Book
It is a CD-ROM data disc standard formulated by Philips and Sony in 1983. This specification contains only data sectors and is divided into two modes.
Mode 1
Error checking and correcting check is added to the CD, and each sector can store 2048 bytes of data, which is suitable for storing conventional data.
Mode 2
The removal of ECC check increases the file storage space, and each sector can store 2336 bytes, which is suitable for storing graphics and music materials.
Defining a unit of 2352 bytes in the Yellow Book is called a block.
(3) Green Paper
Formulated in 1986, it is the standard of CD-I interactive CD.
(4) Yellow Book+(Yellow Book Advanced)
1989, which supplements the CD-ROM/XA (optical disc expansion architecture) standard. Added specification of mode 2:
Form 1: ECC(Error Checking and Correction) check is added, and each sector can store 2048 bytes, which can be used as Mode 1 format.
Form 2 removes ECC checking and increases file storage space. Each sector can store 2328 bytes, which is as suitable for storing graphics and music materials as mode 2.
The greatest use of the enhanced yellow book is that it can alternately store data or audio and video to avoid the intermittent phenomenon when audio and video are transmitted at the same time.
(5) Orange Book
It contains the standard of CD-R recordable discs. The physical structure of CD is defined as: sectors are contained in tracks, tracks are contained in data areas, and data areas are contained in optical disks.
(6) White paper
It defines the standard of VCD (Video Disc).
(7) Blue Book
The standard defines an extra mode optical disc (CD-Extra), and stipulates that the first track is a CD-DA music segment and the second track is a CD-ROM data segment.