This type can be divided into two categories: Standard readable discs only. o Read-only digital discs: this type comes from ROM-CD ORAM 2 The most periodic and complete texts are available on them. 3-3-2-3-2 Disks with write memory once: we can conclude by calling them It is a disk that allows to write on it, and once written, it can be changed, which makes it an advantage There is a larger capacity of read-only discs and these discs are called WORM and there is another type of disc. Single-write discs are called DRAW and allow you to check the data inside. 3 or more groups to ensure that the writing process is correct This type can be divided into: o Unique analog writing discs, specially used by disc manufacturers For the purpose of experimentation and choice o Writing discs unique, widely used in library applications Information centers and archives because they store digital data, regardless of the type of this data. It is designated by: OD3 ODDD. 3-3-2-3-3 Disks with erasable memory: it allows to record information on them Modify it and erase it to write it a second or several times, and this type came to realize the recorded deficiency At the level of the two previous types, this type is called: record 1 compact disc - Ibn al-Sabti, Abd al-Malik. Information technology conferences. Previous reference. 27. Dr Ibn Al-Sabti and Abdul-Malik. Information technology: its types and its role in supporting documentation and scientific research University of Mentouri Constantine 3. - Mujbel, Muslim Maliki, previous reference 148.2. A model: Message from MA Magister in Library and Information Sciences, June 2002 38. R-CD, presented for the first time in March 1997 in Hanover. 1 northern Canada 3-3-2-4 depending on the nature of the storage: the storage is carried out by laser beams in one of the two Analog or digital systems, the optical discs can therefore be divided into two types: 3 -3-2-2-3 Standard optical (analog) discs, which use the method Analog storage, floppy disks belong to this category and are used to store images Cards, shapes, films and TV shows. : Used to record all types of data, 2-3-3-2-2-4 DVD optical Text, images, geometric shapes, sound. It is commonly used in libraries Information centers are characterized by high recovery accuracy and optical discs include several types Are: o ROM - CD - ROM Interactive interactive discs I.CD DRAW direct reading discs o Discs with several readable memories and WORM-CD (ODDD) -OD3: Digital discs o O DVD: read only memory: O