Software Defined Radio (SDR) is a transformative technology that uses software to control radio frequency functions, allowing for flexibility and reconfigurability in wireless communications. Developed in the 1970s and 1980s, SDR offers cost-effectiveness and adaptability compared to traditional radios, with applications in wireless communication, radio astronomy, security, and medical imaging. The future of SDR includes integration with 5G, IoT, AI, and dynamic spectrum sharing.