The upper-left pane in the following screenshot contains a simple C function that adds 2 to the number specified as a parameter. The lower-left pane contains the corresponding Wat:

If this looks familiar, it's because this same code was used for the explanation of Wat's s-expressions in the beginning of this chapter. Digging a little deeper, you can see how the C code corresponds to the Wat output. The addTwo() function is exported from the module as a string on line 5. Line 5 also contains (func $addTwo), which references the $addTwo function on line 6. Line 6 specifies that a single parameter of type i32 (an integer) can be passed in and the result returned is also an i32. Pressing the Build button in the upper-right corner (or above the C/C++ editor) will compile the C code into a Wasm file. The Wasm will be available for download or interaction with JavaScript once the build is completed.