  The theoretical fundamentals of formation of the supernova remnant (SNR)
continuum radio spectra are presented in this review. Mainly based on the Fermi
1 theory - also known as diffuse shock acceleration (DSA) - the different
shapes (linear or curved in log-log scale) of SNR radio spectra are predicted
for both young and evolved SNRs. On the other hand, some particular forms of
spectra of older SNRs can be predicted by including the additional processes
such as Fermi 2 acceleration mechanism or thermal bremsstrahlung radiation.
Also, all of these theoretically predicted forms of radio spectra are compared
with real spectra obtained from observations. Finally this review can represent
some kind of "atlas" with initial patterns for the different kinds of SNR radio
spectra - it should be helpful for radio astronomers in their interpretation of
the observed radio spectra.
