A welcoming environment is one where there is an authentic sense of connection; students feel respected and valued in the classroom. Computing, unfortunately, has become associated with a very specific niche that can often lead to stereotype threat. This can be mitigated by providing your students with a welcoming environment that builds confidence and by showing them relatable role models working in the CS field. Developing a sense of belonging in a CS classroom/career will help boost motivation. A welcoming environment is a key pillar, if they don't feel like they belong, students are less motivated in the course and less likely to take future CS courses.
"Independent of other factors, a sense of belonging in the field of computing was a significant predictor of working or majoring in computer science or computer engineering in our sample" -- NCWIT, Learning from Young Women