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Some pencil cases have a hard and rigid shell encasing the pens inside, while others use a softer material such as plastic, leather or cotton. Soft versions are typically fastened with a zipper. Early pencil cases were round or cylindrical in shape. Some early pencil cases were decorated with jasper (one from 1860) or platinum (from 1874). [1]
A pencil (/ ˈ p ɛ n s ə l / ⓘ) is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage and keeps it from marking the user's hand. Pencils create marks by physical abrasion, leaving a trail of solid core material that adheres to a sheet of paper or other surface.
A mechanical pencil or clutch pencil is a pencil with a replaceable and mechanically extendable solid pigment core called a "lead" / ˈ l ɛ d /. The lead , often made of graphite , is not bonded to the outer casing, and the user can mechanically extend it as its point is worn away from use.
LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 [1] and 1978. [2] They are also known as Lempel-Ziv 1 (LZ1) and Lempel-Ziv 2 (LZ2) respectively. [3]