Defining Characteristics of Cross-Sectional Studies. Think of a cross-sectional study as a snapshot of a particular group of people at a given point in time. Unlike longitudinal studies that look at a group of people over an extended period, cross-sectional studies are used to describe what is happening at the present moment.
Dec. 3, 1992: The first text message Papworth, a former developer at Sema Group Telecoms, sends the world's first SMS greeting to his friend Richard Jarvis, who at the time worked at U.K. service Vodafone. Jarvis couldn't say Merry Christmas back, because his brick-sized Orbitel 901 phone had no way of inputting text.
Optical keyboard technology was introduced in 1962 by Harley E. Kelchner for use in a typewriter machine with the purpose of reducing the noise generating by actuating the typewriter keys.