A computer software developer designs, tests, and develops software to meet user needs. They write code in various languages, like Java or C++, and work on both system and application software. Developers often collaborate with other professionals to determine software requirements, ensuring functionality aligns with client expectations. They conduct testing to identify and fix bugs, ensuring optimal performance. They also document every aspect of an application or system as a reference for future maintenance and upgrades. Additionally, they can create models and diagrams that instruct programmers how to write software code, thus playing a pivotal role in software production.