Question

Consider the following \(\mathrm{C}++\) code: string str1; string str2; char ch; cin \(>>\operatorname{str} 1\) \(\operatorname{str} 2=\operatorname{str} 1\) cin \(>>\mathrm{ch}\) \(\operatorname{str} 2[0]=\mathrm{ch}\) cout \(<<\operatorname{str} 1<\cdots \rightarrow \cdots<<\operatorname{str} 2<<\) end 1 Answer the following questions. a. What is the output if the input is Hello J? b. What is the output if the input is Bingo \(\mathrm{R}\) ? c. What is the output if the input is Sunny B?

Short answer

a. HelloJello, b. BingoRingo, c. SunnyBunny

Step-by-step solution

Understand the Code Flow

The C++ code initializes two strings `str1` and `str2`, and a character variable `ch`. It then takes input for `str1`, sets `str2` equal to `str1`, takes another input for `ch`, changes the first character of `str2` to `ch`, and outputs `str1` and `str2`.

Analyzing Input Case 1 (Hello J)

For input 'Hello J': 1. `str1` becomes 'Hello' after input. 2. `str2` is set to 'Hello'. 3. The character `ch` is set as 'J'. 4. The first character of `str2` changes from 'H' to 'J'. Thus, `str1` remains 'Hello', and `str2` becomes 'Jello'. The output is `HelloJello`.

Analyzing Input Case 2 (Bingo R)

For input 'Bingo R': 1. `str1` becomes 'Bingo' after input. 2. `str2` is set to 'Bingo'. 3. The character `ch` is set as 'R'. 4. The first character of `str2` changes from 'B' to 'R'. Thus, `str1` remains 'Bingo', and `str2` becomes 'Ringo'. The output is `BingoRingo`.

Analyzing Input Case 3 (Sunny B)

For input 'Sunny B': 1. `str1` becomes 'Sunny' after input. 2. `str2` is set to 'Sunny'. 3. The character `ch` is set as 'B'. 4. The first character of `str2` changes from 'S' to 'B'. Thus, `str1` remains 'Sunny', and `str2` becomes 'Bunny'. The output is `SunnyBunny`.

Key concepts

String Manipulation

String manipulation is an essential concept in C++. It involves altering, retrieving, or analyzing data stored in string variables. In our exercise, we see string manipulation through the copying and alteration of string values. When `str2` is initially declared, it is set to be the same as `str1`.
Later, we change the first character of `str2` using the character input `ch`. This showcases how strings are mutable and how individual characters can be accessed and modified using the index notation, much like arrays. C++ strings are powerful, enabling easy operations such as finding length, concatenating, and slicing, which makes them ideal for handling text in various applications.

Input and Output

In C++, input and output operations are performed using `cin` and `cout`, respectively. These operators are part of the iostream library, a core component for handling console I/O.
In the code, the `cin` operator is used to take user inputs for both the string (`str1`) and the character (`ch`). The `cin` operator reads consecutive characters from the input until it encounters whitespace, which is why `str1` catches the whole word before the space. Following this, `cout` is employed to print the results stored in `str1` and `str2`.
Using these operators is simple because they automatically manage the conversion of data types during input and output, providing a streamlined way to handle user interaction with programs.

Character Variables

Character variables in C++ are used to store single characters. In this exercise, the variable `ch` holds a character input provided by the user. These variables have a data type of `char`, capable of storing any character found in the ASCII table.
The use of a character variable allows the program to be flexible in amending string contents, as we change the first character of `str2` to `ch`. Characters are fundamental building blocks in string operations. They facilitate the creation and manipulation of strings by serving as the smallest unit of textual data. C++ uses character constants enclosed in single quotes, and their manipulation is an essential skill in programming across string-related tasks.

Code Analysis

Analyzing code is a vital skill for programmers, allowing them to understand the logic and function of a program. In this C++ exercise, code analysis involves tracing the flow of input and variable changes to predict outputs accurately.
By breaking down the operations step-by-step, we observe how data flows through `cin` into `str1`, how `str2` is derived and then modified, and finally, how results are displayed using `cout`. Understanding such a flow helps in debugging, optimizing code, and ensuring that a program performs the expected operations efficiently.
Code analysis also fosters an enhanced ability to write clean and maintainable code, as it encourages looking at a program from both minute and holistic perspectives, ensuring clarity and purpose in every line written.