英和和英

The H tree (so called because its first two steps resemble the letter "H") is a family of fractal sets whose Hausdorff dimension is equal to 2. They can be constructed by starting with a line segment of arbitrary length, drawing two shorter segments at right angles to the first through its endpoints, and continuing in the same vein, reducing (dividing) the length of the line segments drawn at each stage by √2. Surprisingly, continuing this process will eventually come arbitrarily close to every point in a rectangle, or in other words, the H-fractal is a space-filling curve. It is also an example of a fractal canopy, in which the angle between neighboring line segments is always 180 degrees.

An HTree is a specialized tree data structure for directory indexing, similar to a B-tree. They are constant depth of either one or two levels, have a high fanout factor, use a hash table of the filename, and do not require balancing. Htree indexes are used in the ext3 and ext4 Linux filesystems, and were incorporated into the Linux kernel around 2.5.40.