A software engineer designs, develops, and tests software systems. They use mathematical analysis and computer science principles to create and improve software applications. They often work in a team, collaborating with other engineers, programmers, and designers. They may develop various types of software, including computer games, business applications, operating systems, network control systems, and middleware. They are involved in all stages of software creation, from initial planning and design, through coding, testing, and maintenance. They ensure the software is efficient and reliable, meeting both technical and consumer needs. They may also fix bugs and adapt the software to new hardware.