trees and external storage assume block size of , bytes ( thusour phone book database will require , , bytes divided by , bytes per blockwhich is , blocks your software is most efficient when it specifies read or write operation that' multiple of the block size if you ask to read bytesthe system will read one block , bytesand throw away all but or if you ask to read , bytesit will read two blocksor , bytesand throw away almost half of them by organizing your software so that it works with block of data at timeyou can optimize its performance assuming our phone book record size of bytesyou can store records in block ( , divided by )as shown in figure thusfor maximum efficiency it' important to read records at time (or multiples of this numberfile , , bytes block block block block block , , , bytes record record record record last name last name last name last name first name first name first name first name address address address address phone phone phone phone etc etc etc etc bytes figure blocks and records notice that it' also useful to make your record size multiple of that wayan integral number of them will always fit in block of coursethe sizes shown in our phone book example for recordsblocksand so on are only illustrativethey will vary widely depending on the number and size of records and other software and hardware constraints blocks containing hundreds of records are commonand records may be much larger or smaller than bytes