As shown in Figure 3, the recording tracks (grooves) "wobble" at a fixed frequency, and address pits called Land Pre-Pits are positioned between the recording tracks. (The details of this structure will be explained later.) These two types of addressing are used during recording to control disc rotation and generate the recording clock, as well as providing information such as recording address, which is necessary in the recording process.
After recording, the disc Information Area, the playback region, has exactly the same structure as that of a DVD-ROM disc, and the data format is also exactly the same. Closer to the center of the disc than the Information Area is another region, called the R-Information Area, which is peculiar to DVD-R and DVD-RW discs. This area contains an area called the PCA (Power Calibration Area), which is used for laser power calibration, and an area called the RMA (Recording Management Area), which contains recording management information necessary for the recording device. This information is provided to prevent problems in playing these writable discs in ordinary players and drives.

6.3.1 Preformat and addressing

DVD-R and DVD-RW discs use groove wobble and land pre-pits as a means for providing pre-format. As shown in Figure 3, the disc substrate contains grooves which are used to guide the laser beam, and the data is recorded in these grooves. The areas between adjacent grooves are called lands. Groove wobbling means that the grooves wander back and forth with a fixed amplitude and spacial frequency. Land pre-pits are isolated pits formed on the lands in a fixed pattern. The major uses of these two features are as follows:

		Groove wobbling
	-	generation of a spindle motor control signal
	-	generation of a gate signal used in detection of the land pre-pits Land pre-pits
	-	high-precision positioning when writing data
	-	acquisition of recording address and other information necessary for recording