C++ Primer Plus

C++’s basic types fall into two groups. One group consists of values that are stored as integers. The second group consists of values that are stored in floating-point format. The integer types differ from each other in the amount of memory used to store values and in whether they are signed or unsigned. From smallest to largest, the integer types are bool, char, signed char, unsigned char, short, unsigned short, int, unsigned int, long, unsigned long, and, with C++11, long long, and unsigned long long. There is also a wchar_t type whose placement in this sequence of size depends on the implementation. C++11 adds the char16_t and char32_t types, which are wide enough to hold 16-bit and 32-bit character codes, respectively. C++ guarantees that char is large enough to hold any member of the system’s basic character set, wchar_t can hold any member of the system’s extended character set, short is at least 16 bits, int is at least as big as short, and long is at least 32 bits and at least as large as int. The exact sizes depend on the implementation.

Characters are represented by their numeric codes. The I/O system determines whether a code is interpreted as a character or as a number.

The floating-point types can represent fractional values and values much larger than integers can represent. The three floating-point types are float, double, and long double. C++ guarantees that float is no larger than double and that double is no larger than long double. Typically, float uses 32 bits of memory, double uses 64 bits, and long double uses 80 to 128 bits.

By providing a variety of types in different sizes and in both signed and unsigned varieties, C++ lets you match the type to particular data requirements.

C++ uses operators to provide the usual arithmetical support for numeric types: addition, subtraction, multiplication, division, and taking the modulus. When two operators seek to operate on the same value, C++’s precedence and associativity rules determine which operation takes place first.

C++ converts values from one type to another when you assign values to a variable, mix types in arithmetic, and use type casts to force type conversions. Many type conversions are “safe,” meaning you can make them with no loss or alteration of data. For example, you can convert an int value to a long value with no problems. Others, such as conversions of floating-point types to integer types, require more care.

At first, you might find the large number of basic C++ types a little excessive, particularly when you take into account the various conversion rules. But most likely you will eventually find occasions when one of the types is just what you need at the time, and you’ll thank C++ for having it.

Chapter Review

1. Why does C++ have more than one integer type?

2. Declare variables matching the following descriptions:

a. A short integer with the value 80

b. An unsigned int integer with the value 42,110

c. An integer with the value 3,000,000,000

3. What safeguards does C++ provide to keep you from exceeding the limits of an integer type?

4. What is the distinction between 33L and 33?

5. Consider the two C++ statements that follow:

char grade = 65;

char grade = 'A';

Are they equivalent?

6. How could you use C++ to find out which character the code 88 represents? Come up with at least two ways.

7. Assigning a long value to a float can result in a rounding error. What about assigning long to double? long long to double?

8. Evaluate the following expressions as C++ would:

a. 8 * 9 + 2

b. 6 * 3 / 4

c. 3 / 4 * 6

d. 6.0 * 3 / 4

e. 15 % 4

9. Suppose x1 and x2 are two type double variables that you want to add as integers and assign to an integer variable. Construct a C++ statement for doing so. What if you want to add them as type double and then convert to int?

10. What is the variable type for each of the following declarations?

a. auto cars = 15;

b. auto iou = 150.37f;

c. auto level = 'B';

d. auto crat = U'/U00002155';

e. auto fract = 8.25f/2.5;

Programming Exercises

1. Write a short program that asks for your height in integer inches and then converts your height to feet and inches. Have the program use the underscore character to indicate where to type the response. Also use a const symbolic constant to represent the conversion factor.

2. Write a short program that asks for your height in feet and inches and your weight in pounds. (Use three variables to store the information.) Have the program report your body mass index (BMI). To calculate the BMI, first convert your height in feet and inches to your height in inches (1 foot = 12 inches). Then convert your height in inches to your height in meters by multiplying by 0.0254. Then convert your weight in pounds into your mass in kilograms by dividing by 2.2. Finally, compute your BMI by dividing your mass in kilograms by the square of your height in meters. Use symbolic constants to represent the various conversion factors.