For the given task of storing linguistic data the upper limit is set to 255 bytes for key field and 255 bytes for information one. The size of each record, therefore, varies from 0 to 510 bytes. The concept of binary tree implies several levels of pages with the search starting with the single top-level page and continuing down until the lowest level is reached. Data are stored in such a way as to allow sorted access. Within the framework of the considered model the actual data are stored only at the lowest level of pages while the upper-level pages contain the reference data needed to perform ordered searches.
Upper levels contain the control pages and the lowest levels store the information pages.
The first control page that starts the search in the binary tree is called the root page. Each database consists of several levels of control pages and a single level of information pages. Each page contains records storing sizes of its key and information fields in the first two bytes followed by the values of these fields. The key fields are placed in an increasing order throughout the page and the whole index while information fields could contain any data. Thus the size of each field in the record varies from 0 to 255 bytes and the page is filled without loss of space until it overflows during appending.