Question

Suppose x and y are int variables and ch is a char variable. Consider the following input: 5 28 36 What value (if any) is assigned to x, y, and ch after each of the following statements executes? (Use the same input for each statement.) a. cin >> x >> y >> ch; b. cin >> ch >> x >> y; c. cin >> x >> ch >> y; d. cin >> x >> y; cin.get(ch);

Short answer

a. x = 5, y = 28, ch = '3'; b. ch = '5', x = 28, y = 36; c. x = 5, ch = '2', y = 36; d. x = 5, y = 28, ch = ' '.

Step-by-step solution

Input Description

The input provided is: "5 28 36". This will be used for testing each statement sequentially.

Statement A Analysis

The statement is `cin >> x >> y >> ch;`. This attempts to assign the first integer from the input to `x`, the second integer to `y`, and the remaining character to `ch`. 1. `x` is assigned 5. 2. `y` is assigned 28. 3. `ch` is assigned '3' from the number 36, capturing the first character of what's left in the stream.

Statement B Analysis

The statement is `cin >> ch >> x >> y;`. This assigns the first character from the input to `ch`, followed by any integers. 1. `ch` is assigned '5'. 2. `x` is assigned 28. 3. `y` is assigned 36. This happens because the first character '5' is taken as `ch`, leaving `x` to take the next available integer, which is 28.

Statement C Analysis

The statement is `cin >> x >> ch >> y;`. This means `x` is assigned the first integer, `ch` the next character, and `y` the following integer. 1. `x` is assigned 5. 2. `ch` is assigned '2' from the number 28. 3. `y` is assigned 36. The character '2' is read as `ch` because it is the first character after reading 5 and before reaching the next integer.

Statement D Analysis

The statement is two parts: `cin >> x >> y; cin.get(ch);`. The first part assigns the first two integers, and `cin.get(ch)` reads the next character. 1. `x` is assigned 5. 2. `y` is assigned 28. 3. `cin.get(ch);` reads the space after '28', so `ch` is assigned ' ' (a space character). After reading two integers, the next available character is a space, which is then assigned to `ch`.

Key concepts

cin

In C++, `cin` is an object of class `istream` that represents the standard input stream. It is primarily used to read input from the user, commonly from the keyboard. When you want to collect data from the user, you use `cin` paired with the extraction operator `>>`.

Here’s how `cin` is typically used:

• Each `>>` operator reads data from the input stream, interpreting it according to the type of the variable it directs input into.
• Multiple variables can be listed sequentially with `cin`, separated by the extraction operator.
• The input is generally read from the standard input buffer, which stores input from the user until it's extracted.
• If the expected data type is not met, `cin` will fail, and you will need error handling to clear the state and empty the input buffer.

The role of `cin` is crucial for interactive programs, where the program needs to adjust its behavior based on input data.

variable assignment

Variable assignment in C++ is the process of storing a value in a variable. When using `cin`, you often assign values to multiple variables in one line, providing efficiency and ease of use.

Consider how variable assignment works with `cin`:

• Each `>>` operator extracts data from the input and assigns it to the variable that follows it.
• If the input sequence does not match the expected types, it can lead to unexpected assignments or data loss.
• For several data types, like integers and characters, the order of the `cin` operations is critical—this determines which input item is assigned to each variable.
• Pay attention to the input format, as spaces or unexpected characters can alter the assignment outcomes.

Using variable assignment correctly ensures that the data your program will work with is both accurate and reliable for subsequent operations.

character reading

Character reading is a fundamental concept when handling input in C++. Given the flexibility `cin` offers, it can read characters where specific care is given to the timing and sequence of input operations.

Important points about character reading:

• Characters are read from the input stream as they are, without transforming them based on value like with integers.
• The extraction operator (`>>`) reads a single character separate from any integer adjacent to it in input unless it forms part of a number.
• When using `cin.get()`, you can capture even spaces or newline characters, making it useful for managing complex inputs.
• Distinguishing between numeric and non-numeric input requires strategic reading techniques, especially when numbers may be adjacent or combined.

Understanding how characters are read helps in handling more flexible input scenarios, particularly in text parsing or when mixed data types are expected.

integer reading

In C++, integer reading involves using `cin` to extract numerical data from the input stream. This process is usually straightforward, assuming the input data is well-formatted and matches the expected data type.

Here's how integer reading with `cin` works:

• When using `cin` with `%variable% of type `int`, it reads the input as whole numbers up until a non-numeric character is encountered.
• The reading stops at any whitespace or characters not part of a digit, facilitating easy parsing of typical input formats.
• Multiple integers can be extracted in one `cin` statement, but their exact order is crucial to ensuring correct data assignment.
• If input does not fully match type, such as inserting a letter where a number is expected, it results in errors unless handled properly.

Successful integer reading requires clear expectations of the input format and thorough understanding of how `cin` handles numeric streams.