C-Store is a read-optimized relational DBMS that contrasts sharply with most current systems, which are write-optimized. Among the many differences in its design are: + storage of data by column rather than by row, + careful coding and packing of objects into storage including main memory during query processing, + storing an overlapping collection of column-oriented projections, rather than the current fare of tables and indexes, + a non-traditional implementation of transactions which includes high availability and snapshot isolation for read-only transactions, + and the extensive use of bitmap indexes to complement B-tree structures.