The device used to read information written on a CD-ROM is called a CD-ROM drive. When CD drives were introduced , its data transfer rate was 150 kilobits per second ( KB / S) . This power is expressed by X. Two types of CD-ROM drives are commonly used in microcomputers. Namely - 1. Internal CD ROM Drive: It is installed inside the system unit. 2. External CD ROM Drive: Removal This drive is attached via a port on the motherboard. Drive speed: This drive can be divided into different parts depending on the speed or the ability to transfer data. For example: Single Speed Drive - It can transfer 150 kilobytes of data per second. This power is expressed by X. Double Speed Drive - These types of drives can transfer 2X or 300 kilobytes of data per second. Currently a numeric number is provided with the CD drive. The number is basically a calculation of kilobytes. For example , if a drive has 4X , its data transfer capacity will be 1200 kilobytes / second. Again, if 1800 is written on a drive , then the value of that drive will be (1800 ÷ 150 = 12) 12 X. Data stored in CD ROM such as text , pictures , videos , words , computer games , programs etc. are stored. These CDs are read by ROM drive. That's why the speed of a CD drive is so important. Because reading a large amount of data from a CD requires a fast CD drive , without a fast CD drive the task of reading can become extremely tedious.