The user interface part of an application program can be easily and compactly constructed by combining the parallel execution primitive Linda and the state transition description language Flex with a general purpose programming language. With this approach, a wide range of interfaces can be constructed without using languages or systems specific to user interface design. Using these tools, parallel execution, separation/communication between the application and the interface part, and complicated dialogs can easily be specified. In our implementation, the specification is compiled into C and runs efficiently without any runtime system.