A software-defined radio consists of a programmable communication system where functional changes can be made by merely updating software. In this paper, a software-defined radio 4-QAM (Quadrature Amplitude Modulation) modem system is implemented in LabVIEW. LabVIEW is a widely used graphical programming environment which allows designing systems in an intuitive block-based manner in shorter times as compared to the commonly used text-based programming languages. Basically, this paper demonstrates the ease with which a software-defined radio system can be built and analyzed via the LabVIEW graphical programming environment. Examples are provided to demonstrate the phase and frequency tracking capability of the system.