By default, the input file has an extension of .sqb, but if you use the TARGET precompile option (TARGET ANSI_COBOL, TARGET IBMCOB, TARGET MFCOB or TARGET MFCOB16), the input file can have any extension you prefer.
By default, the output file has an extension of .cbl, but you can use the OUTPUT precompile option to specify a new name and path for the output modified source file.