A brief overview of the results of the study of the red giant Arcturus is given. One-dimensional LTE modeling of the atmospheres of Arcturus and the Sun as a star is carried out on the basis of calculation of the extended wings of the H and K Ca II lines. It is found that the local continuum in this spectral region is underestimated by an average of 12% in the atlases of Arcturus. The average deficit in UV absorption amounts to 43% (Arcturus) and 9% (the Sun). The correction factor to the opacity in continuum for the wavelengths of 390.0, 392.5, 395.0, 398.0, and 400.0 nm equals 2.20, 1.90, 1.70, 1.55, and 1.45 (Arcturus) and 1.20, 1.20, 1.20, 1.17, and 1.15 (the Sun), respectively. Model calculations agree completely with the estimates of the parameters of the Arcturus atmosphere ( T = 4286 K and log g = 1.66) and the elemental abundances that were presented by Ramirez and Allende Prieto [56]. The obtained model of the atmosphere of Arcturus is presented in tabular form. [ABSTRACT FROM AUTHOR]