Computers have evolved greatly over time, starting as simple mechanical aids like the abacus and advancing to modern electronic digital computers. Some key developments include Charles Babbage designing plans for the first general-purpose computer in the 1830s; the creation of the first functional computer called the Mark I by Howard Aiken in 1944; the invention of the transistor in 1948, which made computers smaller and more reliable; the development of programming languages like BASIC in the 1960s; and the creation of early personal computers like the Altair in 1975 and the Apple I in 1976, which helped usher in the personal computer revolution.