We consider several issues in the analysis and design of turbo coded systems for (O, /spl kappa/) input-constrained channels. These constraints commonly arise in magnetic recording channels. This system is characterized by a high-rate turbo code driving a high-rate (n-1)/n, small-length (O, /spl kappa/) block code. We discuss the properties of the (O, /spl kappa/) code that affect its performance on both an additive white Gaussian noise (AWGN) and a precoded dicode channel. We address soft-in soft-out (SISO) decoding of linear and nonlinear (O, /spl kappa/) codes and show that good (O, /spl kappa/) codes exist even when d/sub min/=1. For the (O, /spl kappa/) constrained AWGN channel, we present several rate (n-1)/n block codes that optimally tradeoff bit-error-rate performance with /spl kappa/. For the precoded dicode channel, we show that the systematic (O, n-1) modulation codes are superior to most other rate (n-1)/n block codes in terms of error-rate performance, and their attractiveness is increased by the fact that they do not contribute any significant complexity to the overall system.