When viewing a very large computer file (text file, spreadsheet, or database table), one is usually interested in the data at the beginning and the end of the file, but rarely needs to view any particular record in the middle of the huge file. The thorough user will examine the last few records to make sure all the records are present and verify that there is no truncation or junk at the end of the file.

Most file viewers/editors will display the beginning of the file very quickly, even if it’s a tremendous file size. But when you enter the command to jump to the bottom, you have to wait a long time; this is because the file is stored sequentially on disk or tape and the computer must scroll through the whole thing internally before it can be displayed. Even a keyed index is insufficient because rarely do you know what key you are looking for.

The Ends-First Access Method (or EFAM) is an improvement to pure sequential access, wherein the first records and the last records (a system parameter, such as 1000 or a percentage of the file) are stored on disk/tape at the “front” of the file, and all the middle records come after.

This method could be used for physical storage, too; for example, card catalogs or even books on a shelf in a bookstore. Although each drawer or shelf is labeled, such as Aa - Fr, it would provide an additional, physical reinforcement to see books beginning with Aa, Ab, and then Fq, Fr sitting on the shelf at top left, followed by the rank-and-file Ac, Ad, Ae, etc. For physical things like books, a plastic marker labeled Fq or Fr could stand in for those books if the out-of-order system bothers people.

Thank you.
-- phundug, Dec 30 2010

Unix has the following commands:

head
tail

with various modifiers allowing you to specify how much of the top or bottom of a file you want to look at.

If you want to use these sort of commands, you can use a variety of operating systems that support them (Unix, Linux, Mac OS, and various others) or, you can download and install Cygwin onto your windows machine for a sort of unix-style experience that is almost very nearly reasonably good.
-- zen_tom, Dec 30 2010


Whoa phundug.
-- rcarty, Dec 31 2010


A book (codex or scroll) is organised like this.
-- pocmloc, Dec 31 2010



random, halfbakery