  We report a study of final states containing a W boson and hadronic jets,
produced in proton-proton collisions at a center-of-mass energy of 7 TeV. The
data were collected with the ATLAS detector at the CERN LHC and comprise the
full 2010 data sample of 36 pb^-1. Cross sections are determined using both the
electron and muon decay modes of the W boson and are presented as a function of
inclusive jet multiplicity, N_jet, for up to five jets. At each multiplicity,
cross sections are presented as a function of jet transverse momentum, the
scalar sum of the transverse momenta of the charged lepton, missing transverse
momentum, and all jets, the invariant mass spectra of jets, and the rapidity
distributions of various combinations of leptons and final-state jets. The
results, corrected for all detector effects and for all backgrounds such as
diboson and top quark pair production, are compared with particle-level
predictions from perturbative QCD. Leading-order multiparton event generators,
normalized to the NNLO total cross section for inclusive W-boson production,
describe the data reasonably well for all measured inclusive jet
multiplicities. Next-to-leading-order calculations from MCFM, studied here for
N_jet >= 2, and BlackHat-Sherpa, studied here for N_jet >= 4, are found to be
mostly in good agreement with the data.
