<Tr> <Td> Cohen and Feldmann </Td> <Td> </Td> <Td> DEC PDP - 10 computer, Adage display, push buttons, keyboard, knobs </Td> <Td> Prototype large - molecule crystallographic structure solution system . </Td> </Tr> <Tr> <Td> Stellman </Td> <Td> </Td> <Td> Princeton: PDP - 10 computer, LDS - 1 display, knobs </Td> <Td> Prototype large - molecule crystallographic structure solution system . Electron density map not shown; instead an "H Factor" figure of merit is updated as the molecular structure is manipulated . </Td> </Tr> <Tr> <Td> Collins, Cotton, Hazen, Meyer, Morimoto </Td> <Td> </Td> <Td> CRYSNET, Texas A&M Univ . DEC PDP - 11 / 40 computer, Vector General Series 3 display, knobs, keyboard . Stereo . </Td> <Td> Prototype large - molecule crystallographic structure solution system . Variety of viewing modes: rocking, spinning, and several stereo display modes . </Td> </Tr> <Tr> <Td> Cornelius and Kraut </Td> <Td> 1976 (approx .) </Td> <Td> Univ, of Calif. at San Diego: DEC PDP - 11 / 40 emulator (CalData 135), Evans and Sutherland Picture System display, keyboard, 6 knobs . Stereo . </Td> <Td> Prototype large - molecule crystallographic structure solution system . </Td> </Tr>

Atoms are often drawn as spheres. comment on the use of this representation as a model