For this experiment, we will play around with the integer declarations in the original program.
The integer data type in C++ is denoted with the int
keyword. This is the type used in the declaration of integer
variables.
From the first experiment, you know that you can change the initial
values of i and j by changing the initialization
expression. What happens though, if the initialization expression is
not an integer?
Change the initialization expression of i to be a literal
string instead of an integer. A string begins and ends with double
quotes:
"this is a string"
Consider: if someone told you they were going to give you a hug, but
then kicked you, you'd complain, right? Well, the compiler probably
doesn't have the same emotional connection to an int that you
might have to a hug, but it's still going to complain.
Compile the program.
Question #2.2.1: What is the first error message that the compiler gives you?
Seems like the compiler will save you from making an initialization mistake. The problem here is that a string of characters cannot be turned into an integer very easily. Ask yourself: what is the best integer to represent "this is a string"?
But what if the data types were very similar and could be converted easily?
Change the initialization expression of i to be a literal
character. A character is a single character surrounded by single
quotes: 'f'.
Compile the program.
Question #2.2.2: What is the first error message that the compiler gives you?
You might be very confused at this point because your compiler didn't give you an error message. Some don't. (Answer the previous
question appropriately: "I didn't get an error message.") The int and char data types in C++ are very closely related, and
you probably won't get an error for initializing an int with
a char. This is because a single char is represented
in the computer's memory as an integer. So it's very easy for the
compiler to switch between the two.
Some compilers will issue a warning for this initialization since
often this is a programming mistake; either i should be
declared as a char, or the initialization is wrong. Either
way, it's a warning you should watch out for, just like any compiler
error.
What about a real number, something with a decimal point in it?
Change the initialization of i to be 3.14159 (the
most overused real-number literal in programming examples), and
compile the program.
Question #2.2.3: What is the first error message or warning that the compiler gives you?
Again, you probably don't get a error message, but you might have gotten a warning.
Let's try something really daring: cin. Initialize i
to be equal to cin. It's a completely ridiculous thing to do,
but let's see what the compiler does. Compile the program.
Question #2.2.4: What is the first error message or warning that the compiler gives you?
This time you should get an actual error message.
Restore your program so that i is initialized to a proper
integer.