Import,
Export — import and export in hundreds of formats
ReadList — read unstructured data from a file
FilePrint — display the raw contents of a file
FindList — find strings in lists of files
Read,
Write,
WriteString — read and write individual data elements
Get (
<<) — get
Mathematica expressions from a file (.m file)
Put (
>>),
PutAppend (
>>>) — put
Mathematica expressions into a file (.m file)