The personal computer market was in its early stages in the 1970s. Computers were mainly mainframes and minicomputers used by professionals. The invention of the microcomputer in the late 1970s helped expand the market. Early marketing strategies involved informative advertising to educate customers. Personal computers were marketed as productivity tools for home and office. Distribution was selective through stores like Radio Shack. Pricing used a cost-plus approach to attract early buyers as the industry grew slowly. Celebrities helped promote the new technology through various advertising channels.