Question

34 What value (if any) is assigned to num and discard after each of… # Suppose that num is an int variable and discard is a char variable. Assume the following input data: #34 What value (if any) is assigned to num and discard after each of the following statements executes? (Use the same input for each statement.) a. cin.get (discard); cin >> num; b. discard = cin.peek(); cin >> num; c. cin.get (discard); cin.putback (discard); cin >> discard; cin >> num;

Short answer

a. num = 34, discard = '#' b. num = 34, discard = '#' c. num = 34, discard = '#'

Step-by-step solution

Process Input with cin.get(discard) and cin >> num

The input "#34" is processed where `cin.get(discard)` reads the first character, so `discard` is assigned '#'. Then `cin >> num` reads the next number until it encounters a non-digit character. In this case, it reads '34', so `num` gets assigned the integer value 34.

Examine the Next Character with cin.peek

`discard = cin.peek()` examines the next character without removing it from the input. Initially, the position is at '#', so `discard` is set to '#'. Then, `cin >> num` reads past the '#' to read the integer 34 again. Thus, `num` is still 34.

Read and Put Back the Character with cin.get and cin.putback

First `cin.get(discard)` takes the '#' and assigns it to `discard`. The character is then put back into the input buffer using `cin.putback(discard)`, so the next input is unaffected. `cin >> discard` reads the '#' again and assigns it back to `discard`. Finally, `cin >> num` reads 34, so `num` is 34 at the end.

Key concepts

cin.get()

The function `cin.get()` is a standard input handling function in C++ that allows you to read the next character from the input buffer. Whether you're dealing with spaces, new lines, or other special characters, `cin.get()` will capture them all. It reads a single character and stores it in a variable, which often comes in handy when you want to manage input streams that contain both characters and numeric data.
Suppose we have the input string "#34". When you call `cin.get(discard);`, the `cin.get()` would read and assign the character '#' to the variable `discard`. It stops at this character and returns it without getting rid of it from the buffer's front line. As a result, you can efficiently continue processing the remaining input, knowing that `cin.get()` precisely pulled the next character for your future operations.

cin.peek()

The `cin.peek()` function in C++ is like peeking through a curtain to see what character is coming next in the input stream without actually taking it away from that stream. This function reads the next character from the input without extracting it, leaving it available for future operations.
For instance, involving the string "#34" as input, when you execute `discard = cin.peek();`, the next character, which is '#', is examined. However, it is not removed from the buffer, so `discard` gets assigned to '#'. This feature is extremely useful for previewing what’s coming next without altering the input stream’s position or status. It means the subsequent operations or functions will still see the entire original input from beginning to end, starting from the '#', unless explicitly removed by another operation.

cin.putback()

Combining `cin.get()` with `cin.putback()` allows one to skillfully manage input streams by reading and replacing characters back into the input buffer without permanently discarding them. When `cin.get(discard)` is executed, the character at the current stream position is read and stored in the variable `discard`.
Later, employing `cin.putback(discard)` will revert the last character read back onto the stream. This ability to return a character means that you can "rewind" what the input functions will encounter next, creating opportunities for cleaner control flow in complex input-handling scenarios.
As demonstrated with the input "#34", suppose '# 'is read using `cin.get(discard)`, this character is available for processing. If there's a need to analyze that character again right after reading it, `cin.putback(discard)` gives you the privilege to do so. This utility is particularly handy when you need to check a character before deciding how you'll handle it, ensuring that your input analysis is both comprehensive and flexible.

int and char variable handling

In C++, `int` and `char` are data types that store integer values and single character data, respectively. Proper handling of these variables is an essential skill, particularly when your program involves reading both numbers and non-numeric characters from an input stream.
The separation and correct assignment of input data to each type is crucial. For example, given the input "#34", the goal is to ensure that the character '#' is captured by a `char` variable `discard`, while the numbers '34' are correctly detected and stored in an `int` variable `num`.
Using functionalities like `cin >> num`, the program reads the input until a non-digit is found, and it's possible to parse multiple data types seamlessly while making sense of the diverse input forms entering your program. These distinctions ensure that the data remains precise and readily manageable as you work with varied input data conditions.

• `int` is suitable for whole numbers.
• `char` is ideal for single characters or symbols.
• Ensure the correct mapping of inputs to their respective variable types.

This careful handling assures that users can efficiently separate numerals from non-numeric characters, achieving the clarity needed to perform subsequent operations on the extracted data, accommodating complex input handling scenarios with ease.