Conjugate Gradient and preconditioned CG method.

Help for solving a linear system of Ku=f for given tol=10^-8 and maxiter =1000. I have to find CG and PCG and compare it with matlab pcg and linsolve and visualize the norm of the difference of the solution in every iteration with the final solution to see the convergence. I am new to MATLAB and it would be helpful if anyone can help me with code