prog.cs(4,14): error CS0234: The type or namespace name `Data' does not exist in the namespace `System'. Are you missing an assembly reference?
prog.cs(5,14): error CS0234: The type or namespace name `Drawing' does not exist in the namespace `System'. Are you missing an assembly reference?
prog.cs(8,14): error CS0234: The type or namespace name `Windows' does not exist in the namespace `System'. Are you missing an assembly reference?
Compilation failed: 3 error(s), 0 warnings