The classroom is also a social institution, a value and norm-laden contextual milieu, that assigns role obligation, expectations, and differential status to the human participant. When organizational practices like classroom teaching are deeply institutionalized, and combine both material and symbolic features, they are immune to transformation. Historically the centralized power and influence of the professor, the classroom instructor is hardly extinct. However, the role like that in many other fields, is changing dramatically. While the CD and DVD disks look physically the same, they are dramatically different.
CDs are more prevalent today than DVDs.
DVDs are new technology. Most computers purchased since 1996 have CD players. Computers purchased since 1999 have DVD players. The new DVD players can also play CDs, but CD players won t play DVD s. Because of this storage capacity, a DVD can play a 120 minute digital feature movie full screen at great quality, and thus are being promoted as a replacement for VHS tape.