Question

Which of the following are correct \(\mathrm{C}++\) statements? a. cout \(<<\) "Hello there!" \(<<\) endl b. cout \(<<\) "Hello"; \(<<\) " There! \("<<\) endl c. cout \(<<\) "Hello" \(<<\) " There! \("<<\) endl d. cout \(<<\) 'Hello There!' \(<<\) endl

Short answer

Statements a and c are correct. Statements b and d are incorrect.

Step-by-step solution

Analyze Statement a

Statement a is `cout << "Hello there!" << endl`. This is a correct C++ statement. The string literal `"Hello there!"` is correctly enclosed in double quotes and `endl` is used to insert a newline character. The correct use of `<<` operators allows this line to compile without error.

Analyze Statement b

Statement b is `cout << "Hello" ; << " There! "<< endl`. This statement is incorrect because of the semicolon between the consecutive `<<` operators. The semicolon prematurely ends the expression, causing a syntax error.

Analyze Statement c

Statement c is `cout << "Hello" << " There! "<< endl`. This is a correct C++ statement. The use of consecutive `<<` operators to chain output streams is valid, and each string literal is properly enclosed in double quotes.

Analyze Statement d

Statement d is `cout << 'Hello There!' << endl`. This statement is incorrect because single quotes are used to define a character literal, not string literals. For multiple characters, double quotes are needed to form a string literal.

Key concepts

C++ Output Streams

In C++, output streams are used to send data to various output devices like the console. The `cout` object is a standard output stream in C++ and is used to display output on the screen. The `cout` object is part of the iostream library, so you need to include `#include ` at the beginning of your C++ programs. This enables C++ programs to make use of input and output routines.
The output stream operator `<<`, often referred to as the insertion operator, directs data from a variable or a piece of text to the output stream. For instance, `cout << "Hello!"` sends the string literal "Hello!" to the console.

• The `<<` operator can chain multiple outputs together, such as `cout << "Good" << " Morning!"`.
• Using `<< endl` appends a newline at the end of the output.

These mechanisms make the `cout` object extremely versatile for displaying different types of information.

String Literals

In C++, a string literal is a sequence of characters enclosed in double quotation marks. String literals are used to represent and manipulate text in a C++ program. They are a way to store text directly within your code.
String literals can be passed directly to the `cout` object to be printed to the console. For example, `cout << "Welcome to C++ Programming!"` displays the message within the quotes on the screen.

• A string literal starts and ends with double quotes (`"`).
• It can contain any number of characters, including spaces and punctuation marks.

String literals are different from variables in that they represent fixed content within the code, unlike variables which can change during execution.

Syntax Errors

Syntax errors occur when a program's source code is not correctly formed according to the rules of the programming language, in this case, C++. Syntax errors can prevent the program from compiling, making it crucial for programmers to ensure code is correctly written.
For instance, in statement b from the exercise, the presence of a semicolon within a `cout` statement causes a syntax error: `cout << "Hello" ; << " There! " << endl`. This error occurs because the semicolon signifies the end of the statement, thus prematurely closing the `cout` expression before it completes, leading to failure in compiling. To fix such errors:

• Do not place semicolons within a chained operator expression.
• Ensure all quotations and parentheses are correctly matched.

By avoiding these common mistakes, you can write clean and correct C++ code.

Character vs String Literals

Character literals and string literals are two different ways to represent text, but they serve different purposes in C++.
A character literal is used to represent a single character and is enclosed in single quotes, like `'A'`. In contrast, a string literal represents one or more characters enclosed in double quotes, like "Apple".
The misuse of these can lead to errors, such as in statement d of the exercise, where single quotes were mistakenly used to denote a string: `cout << 'Hello There!' << endl`. This results in an error because single quotes should only contain one character, and `cout` is expecting a string, which should be denoted by double quotes. To avoid such misunderstandings:

• Use single quotes for a single character (e.g., `'x'`).
• Use double quotes for strings (e.g., "example").

Understanding these basic differences helps avoid common compilation issues.