Evolution tracks in the Hertzsprung–Russell diagram of the stars with a different initial mass and rotational velocities in panel (a). Each curve with different colours refers to a different mass. Panel (b) shows the evolutionary curves in the log T_eff − log g diagram. Point A denotes the zero age main sequence and point B represents the turn-off point of the MS. Point C is the stage of the first dredge-up. Points D, E, and F are the beginning (i.e. the tip of red giant star), midpoint, and end of lithium enrichment. Point G is the local maximal luminosity next to an RC star and point H is the core-helium exhaustion.