The block size can range from 512 upwards as long as the block size is a power of 2. Some systems put the upper limit of 131072 bytes. The original author might just wanted to set some reasonable default block size, not too low and not too high. If you really ask why s/he chose that number, heck I don't know. Perhaps, if you're studying the whole context of the program you'll find out. Or, you may want to ask the author of
. Oracle for example, by some references, uses this number as the default value for data buffering.