This document discusses causality and stability in digital signal processing. It covers impulse response, how response is determined through convolution sums, the concepts of causality and stability, and provides two example problems. Causality means the response of a system depends only on current and past inputs, not future inputs. Stability refers to a system where the response remains bounded for any bounded input signal. The document serves as lecture material from the Department of Electrical and Electronics Engineering at National Engineering College.