... since they first met in 1998. Their first book, Applied Software Project Management, was published by O’Reilly in 2005. They published their first book in the Head First series, Head First PMP, ... variables before you use themTry putting these statements into a C# program: int z; MessageBox.Show(“The answer is ” + z);Go ahead, give it a shot. You’ll get an error, and the IDE will refuse ... useful typesEvery variable has a type that tells C# what kind of data it can hold. We’ll go into a lot of detail about the many different types in C# in Chapter 4. In the meantime, we’ll concentrate...