SCAN: In SCAN algorithm the disk arm moves into a particular direction and services the requests coming in its path and after reaching the end of disk, it reverses its direction and again services the request arriving in its path. So, this algorithm works like an elevator and hence also known as elevator algorithm. As a result, the requests at the midrange are serviced more and those arriving behind the disk arm will have to wait.
Advantages:
High throughput
Low variance of response time
Average response time
Disadvantages:
Long waiting time for requests for locations just visited by disk arm
CSCAN: In SCAN algorithm, the disk arm again scans the path that has been scanned, after reversing its direction. So, it may be possible that too many requests are waiting at the other end or there may be zero or few requests pending at the scanned area.
These situations are avoided in CSAN algorithm in which the disk arm instead of reversing its direction goes to the other end of the disk and starts servicing the requests from there. So, the disk arm moves in a circular fashion and this algorithm is also similar to SCAN algorithm and hence it is known as C-SCAN (Circular SCAN).
Advantages:
Provides more uniform wait time compared to SCAN
Reference : http://geeksquiz.com/disk-scheduling-algorithms/
** I don't know what kind of different implementation you have found. Can you please mention that also?
Any way the above explanation for both the algorithms are good and its same as in Galvin so you can follow this.