  Shocks of supernova remnants (SNRs) accelerate charged particles up to 100
TeV range via diffusive shock acceleration (DSA) mechanism. It is believed that
shocks of SNRs are the main contributors to the pool of Galactic cosmic rays,
although it is still under debate whether they can accelerate particles up to
the "knee" energy (10^15.5 eV) or not. In this chapter, we start with
introducing SNRs as likely sources of cosmic rays and the radiation mechanisms
associated with cosmic rays (section 3). In the section 4, we summarize the
mechanism for particle acceleration, including basic diffusive shock
acceleration and nonlinear effects, as well as discussing the injection
problem. Section 5 is devoted to the X-ray and gamma-ray observations of
nonthermal emission from SNRs, and what these reveal about the cosmic-ray
acceleration properties of SNRs.
