  The ARGO-YBJ detector, located at high altitude in the Cosmic Ray Observatory
of Yangbajing in Tibet (4300 m asl, about 600 g/cm2 of atmospheric depth)
provides the opportunity to study, with unprecedented resolution, the cosmic
ray physics in the primary energy region between 10^{12} and 10^{16} eV. The
preliminary results of the measurement of all-particle and light-component
(i.e. protons and helium) energy spectra between approximately 5 TeV and 5 PeV
are reported and discussed. The study of such energy region is particularly
interesting because not only it allows a better understanding of the so called
'knee' of the energy spectrum and of its origin, but also provides a powerful
cross-check among very different experimental techniques. The comparison
between direct measurements by balloons/satellites and the results by surface
detectors, implying the knowledge of shower development in the atmosphere, also
allows to test the hadronic interaction models currently used for understanding
particle and cosmic ray physics up the highest energies.
