This chapter briefly introduces the readers to the preliminary ideas on design and analysis of computer-controlled systems and then sliding mode control (SMC). In general, computer-controlled systems consist of both continuous and discrete-time systems that interact among themselves through the feedback channel to achieve certain objectives. Different available classical techniques, namely emulation, discrete-time and hybrid approaches, are summarized here with their own advantages and disadvantages. In almost all these techniques, the periodic sampling interval is often used to design and analyse the sampled-data systems for its simplicity and easier in design. On the other hand, aperiodic control implementation is desired in sampled-data systems to reduce the periodic computational burden and cost associated with the implementation. However, this introduces few difficulties in analysing closed loop system stability. © Springer International Publishing AG, part of Springer Nature 2018.