Lexmark C752 Technical Reference page 225

Note: Some printer models released in the year 2000 or later designated as Energy
Star printers cannot have Power Saver disabled.
This operator is equivalent to executing the following PostScript emulation
sequence:
currentpagedevice /PowerSave get
Error: stackoverflow
ramsize
queries the current setting of the RamSize system parameter. An integer is
returned on the stack showing total RAM in bytes.
This operator is equivalent to executing the following PostScript emulation
sequence:
currentsystemparams /RamSize get
Error: stackoverflow
realformat
returns a boolean with the same value as the RealFormat system parameter. It
indicates the printer microprocessor native real number representation. A query
determines if the printer real number representation matches the application real
number representation and compensates if necessary.
Error: stackoverflow
renamefile
renames the oldfilename to the newfilename. This operator is in systemdict.
Errors: invalidfileaccess, ioerror, stackunderflow, typecheck,
undefinedfilename
Note: An undefinedfilename error occurs if the file does not exist.
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PostScript