Today, most keyboards use one of three different mechanical layouts, usually referred to as simply ISO, ANSI, and JIS.
Keyboard layout in this sense may refer either to this broad categorization or to finer distinctions within these categories.The extended keyboards have 110, 109, and 112 keys (ISO, ANSI, and JIS, respectively), and the compact models have 79, 78, and 80.
Keyboard layout is based on user preference, but the 60% has been the most popular in the custom scene, especially for parts avaliability. The compact layouts such as 60%, 75% and TKL (Ten Keyless) do not have a number pad.
75% ANSI Layout