Question

Assume c is a char variable. What value does c hold after each of the following statements executes? Statement \(\quad\) Contents of \(c\) \(c=\) toupper \(\left(^{\prime} a^{\prime}\right)\) ___ \(c=\) toupper \(\left(^{\prime} B^{\prime}\right)\) ___ \(c=\) tolower \(\left(^{\prime} D^{\prime}\right)\) ___ \(c=\) toupper \(\left(^{\prime} e^{\prime}\right)\) ___

Short answer

Answer: 1) 'A' 2) 'B' 3) 'd' 4) 'E'

Step-by-step solution

Statement 1: toupper('a')

The input is 'a', which is a lowercase letter. The toupper function will convert it to its uppercase counterpart. So, the contents of variable 'c' would be 'A'.

Statement 2: toupper('B')

The input is 'B', which is an uppercase letter. Since it's already in uppercase, the toupper function will not change it. So, the contents of the variable 'c' would remain 'B'.

Statement 3: tolower('D')

The input is 'D', which is an uppercase letter. The tolower function will convert it to its lowercase counterpart. So, the contents of the variable 'c' would be 'd'.

Statement 4: toupper('e')

The input is 'e', which is a lowercase letter. The toupper function will convert it to its uppercase counterpart. So, the contents of the variable 'c' would be 'E'.

Key concepts

toupper function

In C++, the **toupper** function plays an instrumental role in transforming characters. Its primary purpose is to convert a given lowercase letter to its corresponding uppercase form. When using **toupper**, you provide it with a character, and it checks if that character is lowercase.
If it is, the function converts it to uppercase. If the character is already uppercase or not a letter, there is no change.
It's crucial to remember that **toupper** works on single characters, specifically those of the `char` data type, which we'll delve into further in another section. Here's a simple illustration: - For `toupper('a')`, the output is `'A'` - For `toupper('B')`, the output remains `'B'` because it's already uppercase Understanding **toupper** is essential when case consistency matters, such as formatting user input or preparing data for case-sensitive operations in C++.

tolower function

Analogous to **toupper**, the **tolower** function aids in converting uppercase letters to their lowercase counterparts. In C++, this function takes a character and tests if it is uppercase. If so, **tolower** changes it to lowercase.
If the character is lowercase or a non-letter, no transformation occurs.
This function is especially useful when uniformity in data entry is needed, or when performing operations not case-sensitive. Working similarly to **toupper**, **tolower** accepts `char` type variables. Examples include: - `tolower('D')` converts to `'d'` - `tolower('e')` remains `'e'` since it's not uppercase The balance between **toupper** and **tolower** allows developers to quickly manage string data in a case uniform way.

char data type

In C++, the **char** data type is a fundamental way to store and manipulate characters. A **char** variable can hold a single character, such as a letter, number, or symbol. Each **char** occupies one byte of memory.
When dealing with character manipulation functions, such as **toupper** and **tolower**, these functions expect **chars** as input.
A few key points about the **char** data type: - **char** can store values expressed in single quotes, like `'A'` or `'4'` - Besides letters, it can hold special symbols like `'#'` Using the **char** data type effectively allows detailed control over text processing. This becomes critical in tasks like parsing user inputs or when designing programs to interact with text data.

uppercase and lowercase conversion

One of the core aspects of programming in C++ is properly managing text data, which often requires converting between uppercase and lowercase characters. Functions like **toupper** and **tolower** are powerful tools for this purpose.
Uppercase and lowercase conversions allow consistent data formatting. This is vital, especially when dealing with case-sensitive systems or when human-readable outputs need standardization.
The conversion is simple: - Use **toupper** to shift any lowercase character into uppercase - Use **tolower** for changing any uppercase character to lowercase These transformations make text checks more predictable. For example, they can simplify checking whether user input equals 'yes' or 'Yes'.

• Converting "yes" and "YES" can be standardized to a format.
• This avoids logical errors in string comparisons.

Understanding and utilizing these conversions efficiently can significantly enhance the accuracy and user-friendliness of software programs.