The C horizon is below the A and B horizons of most soils. It consists of materials that were little altered by the soil-forming processes, though the materials may be modified by weathering. Below the C horizon in some soils is an R horizon of consolidated bedrock, such as limestone, shale, or sandstone.
Ultrabooks Guide. If you want one of the most portable computers on the market, consider getting an Ultrabook, a new kind of super-thin, ultra-light laptop that wakes from sleep quickly and offers a compelling Windows 8 experience.
Hardware, software and performances. The latest Macbook Air and ultrabook generations are motorized by fairly similar Intel Broadwell hardware platforms, with options for Intel Core i5 and i7 processors for the MBA, and also some entry-level Core i3s on ultrabooks.