Question

Assume the following declaration appears in a program: Declare string str = "World" Write a statement that inserts the string "Hello " at the beginning of the str variable. After the statement executes, the str variable should contain the string "Hello world".

Short answer

Answer: You can insert "Hello " at the beginning of the string variable str using string concatenation. Declare the initial string variable str as "World", then concatenate the string "Hello " with str as follows: str = "Hello " + str. The final output will be "Hello World".

Step-by-step solution

Declare the initial string variable str

First, declare the string variable str with the value "World": Declare string str = "World"

Insert "Hello " at the beginning of str

Next, use string concatenation to insert the string "Hello " at the beginning of the str variable: str = "Hello " + str As a result, after executing this statement, the str variable will contain the string "Hello World".

Key concepts

String Concatenation

String concatenation is a foundational concept in programming where you combine, or 'concatenate', two or more strings end-to-end to form a new string. Think of it like connecting train cars: each string is its own compartment, and when you concatenate them, you're linking them together to make one longer train.

In many programming languages, this is done using the '+' operator. For example, if you have a string variable containing the word 'Hello' and another with the word 'World', concatenating them with 'Hello ' + 'World' would result in 'Hello World'. This operation is essential for creating dynamic messages, generating output based on user input, or simply combining static strings in your code.

Programming Variables

Variables in programming are placeholders or containers for storing data values. In a way, a variable is like a labeled box where you can put something inside, and whenever you need it, you can find it by the label. In our case, the 'str' variable is like a label on a box containing the string 'World'.

Variables are defined with a specific type, which determines the kind of data you can store in them. For example, an 'int' variable holds integer numbers, and a 'string' variable holds sequences of characters. Using meaningful variable names is crucial since it makes your code more readable and maintainable. A variable's value can be changed or manipulated throughout the program, which allows for dynamic and flexible programming behavior.

String Variables

String variables are a type of variable that specifically holds sequences of characters, which you can think of as words or sentences. As with our 'str' variable, which holds 'World', strings are typically enclosed in quotes. They can include letters, digits, spaces, symbols - basically any text you want to store and manipulate.

In the context of our exercise, when we 'insert' 'Hello ' at the beginning, we're not pushing the characters into the middle of 'World' but rather creating a new string by concatenating 'Hello ' with 'World' and then updating the 'str' variable to hold this new string. It's important to understand that strings in many programming languages are immutable, which means you cannot change them once they are created; instead, you create new strings through operations like concatenation.