OPEN -- open input file

IO_UNIT = $\langle{\tt integer:1}\rangle$	21	IO unit for file operations
OBJECTS_FILE = $\langle{\tt string:1}\rangle$	'top.out'	filename
FILE_ACCESS = $\langle{\tt string:1}\rangle$	'SEQUENTIAL'	file access: 'SEQUENTIAL' | 'APPEND'
FILE_STATUS = $\langle{\tt string:1}\rangle$	'UNKNOWN'	file status: 'UNKNOWN' | 'OLD' | 'NEW'
NUMBER_LINES = $\langle{\tt integer:1}\rangle$	0	number of lines in the newly opened file

Description:

This command opens a specified file on the specified I/O stream for formatted access. FORTRAN conventions apply to FILE_ACCESS and FILE_STATUS. NUMBER_LINES will contain the number of lines in the file (if opened for reading).