Question

Assume a program has the following variable definitions int \(a, b=2\) double \(c=4.3\) and the following statement: \(a=b * c\) What value will be stored in a?

Short answer

A) 8.6 B) 9 C) 8 D) 7

Step-by-step solution

Analyze data types and their initial values

Here we have three variables. First, \(a\) is an integer without an initial value. Second, \(b\) is an integer with an initial value of \(2\). Third, \(c\) is a double, which is a floating-point number with an initial value of \(4.3\). So, we have: - int \(a\) - int \(b = 2\) - double \(c = 4.3\)

Perform the arithmetic operation

The arithmetic operation to perform is: \(a = b * c\). We have \(b = 2\) and \(c = 4.3\). When we multiply \(b * c\), we get \(2 * 4.3 = 8.6\). But, we need to store this result in an integer variable \(a\).

Understand type casting and store the result

Since \(a\) is an integer, it cannot store a floating-point value like \(8.6\). Hence, an implicit type cast will be done to convert the result into an integer. This is done by truncating the decimal part. So, \(8.6\) becomes \(8\). Thus, the value of \(a\) after the operation will be 8. In conclusion, after performing the arithmetic operation \(a = b * c\), the value stored in the integer variable \(a\) will be 8.

Key concepts

Implicit Type Conversion

When programming in C++, variables can sometimes change their data type unexpectedly. This phenomenon is known as implicit type conversion, or 'type coercion'. It occurs during operations between different data types, for instance, between an integer and a double. In the provided exercise, when the integer variable b multiplies with the double variable c, the result would naturally be a floating-point number.

To store the result in an integer variable a, C++ automatically modifies the data type of the result to match the data type of a, which means the decimal part of the number is truncated, not rounded. It's critical to be aware of implicit type conversion as it can lead to loss of information, as illustrated when the actual operation result of 8.6 is stored as 8 in an integer type.

Arithmetic Operations in C++

Working with arithmetic in C++ involves operators such as addition (+), subtraction (-), multiplication (*), and division (/) among others. These operations can be used on variables and constants to perform calculations.

In the exercise, the multiplication operator (*) is used to calculate the product of b and c. The rules of arithmetic operations in C++ state that operands of differing data types will cause an implicit conversion to the higher precision data type before the operation is performed. However, in storing the result, if the target variable (in this case a) has a lower precision (it's an integer), the value is adjusted accordingly, leading to truncation for floating-point to integer assignment.

Variable Initialization in C++

In C++, you can declare a variable without immediately giving it a value, also known as 'initializing' it. However, it's often a good practice to initialize variables as you declare them to avoid unexpected behavior.

In this problem, b is initialized with the value 2, and c with 4.3 upon declaration. This ensures that when they are used in subsequent operations, the values are known and predictable. Not initializing a right away is acceptable because it’s assigned a value—based on the result of multiplying b * c—before it’s used.

Integer and Double Data Types

Data types are crucial in determining what kind of data a variable can hold in C++. The int data type is used for variables that store whole numbers without any fractional or decimal part, while double can store large floating-point numbers, with significant digits after the decimal.

Understanding this is important because when mathematical operations involve both integers and doubles, as in the exercise, the result must conform to the variable type in which it's being stored. If an operation involves an int and a double, expecting an integer result requires caution due to the implicit type conversion that may lead to data loss.