This computer exercise is given to expose signals and systems (S&S) students to select applications of discrete- time signals and systems. We provide two groups of exercises; one on digital filters and one on spectral analysis using the FFT. We use the NSF funded Java-DSP environment to perform the computer exercises. First, general information on J-DSP is given to enable students to establish and run simple J-DSP simulations. It is important for the students to read this section carefully and go through the initial steps so as to become familiar with the software. The development of the exercises and their assessment are part of an effort to enhance the educational experience of S&S students by exposing them to simple DSP applications. It is also within the objectives of an NSF joint Curriculum and Research Development and Educational Innovation project (NSF CRCD-EI) that aims to introduce junior-level undergraduate students to DSP algorithms and research.