Question

Assume a program has the following variable definitions \\[ \begin{array}{l} \text { Int a, b = 2: } \\ \text { double } c=4.3: \end{array} \\] and the following statement: \\[ a=b \cdot c: \\] What value will be stored in a?

Short answer

Answer: The value of 'a' will be 8.

Step-by-step solution

Identify given values

In the exercise, we have variable definitions, where 'b' is an integer with a value of 2, and 'c' is a double with the value of 4.3.

Analyze the statement

The statement given is: \\[ a = b \cdot c \\] This means we have to find the product of 'b' and 'c' and assign this value to the 'a' variable.

Perform the calculation

As per the given statement, we need to multiply the values of 'b' and 'c': \\[ a = 2 \cdot 4.3 = 8.6 \\]

Assign the result to 'a'

Since 'a' is an integer type variable, it cannot store decimal values. Therefore, the value 8.6 will be truncated to 8: \\[ a = 8 \\] Now, after executing the statement, the value of 'a' will be 8.

Key concepts

Data Types

In C++ programming, data types define the type of data a variable can hold. It helps the compiler understand how the programmer intends to use the data. The primary data types are:

• Integer (int): Used for whole numbers without any fractional component. Examples include -3, 0, 42.
• Floating Point (double, float): These hold numbers with fractions. "double" offers more precision than "float". An example of a floating-point number is 4.3, as seen in the exercise.
• Character (char): Used to store individual characters, like 'a' or 'Z'.
• Boolean (bool): Represents 'true' or 'false'.

Choosing the correct data type is crucial. For example, in our exercise, 'b' is an integer due to its whole number nature, while 'c' is a double to accommodate its fractional part of 4.3.

Variable Assignment

Variable assignment in C++ is a crucial operation that allows you to initialize or update the value of a variable. In the exercise, we see the assignment in action with two statements. Initially:

• b = 2: Here, we're assigning the integer value 2 to the variable 'b'.
• c = 4.3: This assigns the floating-point value 4.3 to 'c'.

Later, when you see a = b * c, the expression on the right side of the equals sign is first evaluated. The result is then assigned to 'a'. If 'a' was not able to hold the type of value resulting from this expression (like a fractional number), additional considerations like type conversion might come into play, which we'll discuss next.

Type Conversion

Type conversion, or type casting, is converting one data type into another. This can happen automatically or be explicitly defined by the programmer. In our original problem, as C++ evaluates the expression a = b * c, there is an implicit type conversion. This means the compiler converts the types in an expression to a common type automatically.

• Implicit Conversion: Also known as type promotion, it occurs when variables are automatically converted. Here, the integer 'b' is converted to double to match 'c' when computing b * c resulting in 8.6.
• Explicit Conversion: Also called type casting, it's explicitly handled by programmers using methods like static_cast.<DataType>(variable).

After the multiplication, the result should be stored in 'a', an integer. Therefore, 8.6 is truncated to 8. This loss of the fractional component occurs because 'a' can only hold integer values.