Flavour Changing Neutral Current Processes and CKM Phenomenology

Some selected topics in flavour changing neutral current processes in $B$ decays are discussed in the context of the Standard Model. The emphasis here is on the determination of the CKM matrix elements from the ongoing and forthcoming experiments. The topics discussed include: (i) CKM-allowed radiative decays $B\to X_s+\gamma$, (ii) CKM-suppressed radiative decays $B \to X_d + \gamma$,$B^\pm \to \rho^\pm + \gamma$and$B^0 \to (\rho^0,\omega) + \gamma$,(iii)$B^0 - \bar{B^0}$-mixings, and (iv) the Fleischer-Mannel bound in $B\to K\pi$ decays.