page_title: 4
section_title: In technology
hierarchical_section_title: 4 / In technology
context_page_description: 4 is a number, numeral, and glyph. It is the natural number following 3 and preceding 5. It is the smallest composite number, and is considered unlucky in many East Asian cultures.
context_section_description: The resin identification code used in recycling to identify low-density polyethylene.
  Most furniture has four legs – tables, chairs, etc.
  The four color process (CMYK) is used for printing.
  Wide use of rectangles (with four angles and four sides) because they have effective form and capability for close adjacency to each other (houses, rooms, tables, bricks, sheets of paper, screens, film frames).
  In the Rich Text Format specification, language code 4 is for the Chinese language. Codes for regional variants of Chinese are congruent to 4 mod 256.
  Credit card machines have four-twelve function keys.
  On most phones, the 4 key is associated with the letters G, H, and I, but on the BlackBerry cellular phone, it is the key for D and F.
  On many computer keyboards, the "4" key may also be used to type the dollar sign ($) if the shift key is held down.
  It is the number of bits in a nibble, equivalent to half a byte
  In internet slang, "4" can replace the word "for" (as "four" and "for" are pronounced similarly). For example, typing "4u" instead of "for you".
  In Leetspeak, "4" may be used to replace the letter "A".
  The TCP/IP stack consists of four layers.
caption: 4 as a resin identification code, used in recycling.