Inputs are mandatory in any system. In computer-based systems, we receive inputs from various sources, including flat files, database tables, keyboards, CD/DVDs, another computer, the Internet, another program on the same computer, another machine, and so on. These inputs come in various formats and forms. One common phenomenon we encounter while receiving inputs from any source is the “garbage in garbage out” (GIGO) factor. We need to validate every piece of data item and only then should we allow it into our application. We need to perform a range of checks on numeric data and logical checks on numeric and alphanumeric data. When we receive input from users, it is usually through a screen on which we prompt the user to input the right data into our system. We need to design a screen aesthetically and functionally. While graphics designers ensure the aesthetic aspects, we software designers need to ensure functional and ease-of-use aspects. We need to place the data controls logically on the screen and minimize the typing effort by presenting opportunities for selecting from presented choices. We need to make choices about the right type of data control for each of the data inputs. In these days of globalization, we need to provide the prompts in multiple languages. All these aspects and others are discussed in this chapter.