Wolfram Language & System 10.4 (2016)|Legacy Documentation
The Wolfram Language automatically handles hundreds of data formats and subformats—all coherently integrated through the Wolfram Language's uniform use of symbolic expressions. For each particular format, the correspondence between representations inside and outside the Wolfram Language can be specified at any level of detail using the Wolfram Language's general data elements mechanism.
Import — import from files and URLs
Export — export data, graphics, and expressions to files
NotebookImport — import specified elements from a notebook
Missing — symbolic representation of missing data
DeleteMissing — delete all missing data