CD-writeover

The traditional aluminum CD is thought to be perhaps the best example of a "write once" medium - to my best knowledge, no one has ever written on such a disk after it came out of the stamping press. However, the aluminum layer is very thin, and there is no reason why a sufficiently powerful laser could not write on the disk. It may even be that existing CD-R drives could do it, at their sustained maximum power level. However, the hardware aspect of this idea is not the most interesting one. Given the desire, one *could* design a CD-R drive which could pit an aluminum disk. The most interesting problem is a software riddle - how does one write to a disk with a relatively chaotic mixture of ones and zeros already present? I propose two solutions. Both involve creating new formats of compact disk data storage. The first, simplest one is to utilize the unused space present on most disks (AOL CDs come to mind.) As a marker for the machine to recognize the file system, record a large block of consecutive one's at the beginning of the disk. (remember, in this system we can make a Zero into a One, but not vice versa.) Then, a second format is utilized - the chaotic data found on the disk is written over in such a way that each logical "one" is converted into a huge sequence of consecutive physical "ones", and the same for 0's. The small block of data written in this way serves as a pointer to the beginning of the free space left over from the unwanted conventional recording. The *second* method, one which is appropriate for disks with no unused space, is to use the consecutive block format for the entire disk. This would result in a capacity perhaps one tenth of what is normal; however, it is arguably better to store 65 meg. on an AOL CD-R than to microwave it, etc. *** For those who are confused, the best analogy for understanding the software aspect of this idea is the fact that one can indeed write legibly on a sheet of paper covered 50% with black dots, if one uses a very thick marker.