Sams Teach Yourself C in 21 Days

The C++ Programming Language 653

BD2

The C++ Data Types ..........................................................................................

In Day 3, “Storing Information: Variables and Constants,” you learned about the C data

types. The same data types are all available in C++. In addition to the data types pre-

sented in Day 3, there are two additional data types commonly used in C++. The first is

thebooldata type. A boolis a Boolean number that is stored in a single byte. The value

of a boolis either TrueorFalse.

Remember that Falseis considered 0 andTrueis considered any other

Note number.

In addition, C++ adds the capability to package data in a format called a class. Classes

define objects in C++. Classes will be covered in detail in tomorrow’s lesson.

Declaring Variables in C++ ................................................................................

Another difference you’ll find in C++ is tied to the declaration of variables. In C, you are

only allowed to declare a variable at the beginning of any block. The most common

place to declare a variable in C is at the beginning of a function; however, it is also pos-

sible to declare a variable in other locations as long as it is at the start of a block.

In C++, you can declare a variable at any time. This means that you can wait to declare a

variable until you are ready to use it. After they are declared, basic variables will stay in

scope until the current block ends. Listing B2.4 illustrates this capability to declare a

variable at any point.

LISTINGB2.4 vars.cpp. Declaring variables in locations other than the beginning of a

block

1: //Showing variable declarations the C++ way

2: #include <iostream.h>

3:

4: int main(int argc, char* argv[])

5: {

6: char a_char = ‘x’;

7:

8: for (int ctr = 1; ctr < 10; ctr++ )

9: {

10: cout << “\nLine: “ << ctr << “ - printing the char: “ << a_char;

11: }

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