(a) Convective core for nonrotating single stars with different convective criteria as a function of evolutionary ages. (b) Convective core for single stars with different various metallicities and rotational velocities as a function of evolutionary ages. (c) Convective core for the donor star (solid lines) and the accreting star (dashed lines) in the binary system with differential orbital period as a function of evolutionary ages. (d) Convective core for two components in the binary system with different metallicities and stellar mass as a function of evolutionary ages.