Control Statements

In C++, control statements are the building blocks that dictate program execution flow. They empower us to make decisions, handle edge cases, and build responsive applications. This section dives into two essential constructs: if / else and switch. These tools form the backbone of conditional logic in your codebase.

if / else

The if / else statement is C++’s most versatile conditional construct. It evaluates a boolean expression and executes one of two code blocks based on whether the expression is true or false. This structure is indispensable for handling real-world scenarios where decisions depend on runtime conditions.

Here’s the core syntax:

<code class="language-cpp">if (condition) {
<p>    // Code to execute if condition is true</p>
<p>} else {</p>
<p>    // Code to execute if condition is false</p>
<p>}</code>

Let’s walk through practical examples that demonstrate real-world applications:

Example 1: Basic positive/negative check

<code class="language-cpp">#include <iostream>

<p>int main() {</p>
<p>    int num = -5;</p>
<p>    if (num > 0) {</p>
<p>        std::cout << "Positive number";</p>
<p>    } else {</p>
<p>        std::cout << "Non-positive number";</p>
<p>    }</p>
<p>    return 0;</p>
<p>}</code>

Output: Non-positive number

Example 2: Grade conversion with else-if chain

<code class="language-cpp">#include <iostream>

<p>int main() {</p>
<p>    int score = 78;</p>
<p>    if (score >= 90) {</p>
<p>        std::cout << "A";</p>
<p>    } else if (score >= 80) {</p>
<p>        std::cout << "B";</p>
<p>    } else if (score >= 70) {</p>
<p>        std::cout << "C";</p>
<p>    } else {</p>
<p>        std::cout << "D";</p>
<p>    }</p>
<p>    return 0;</p>
<p>}</code>

Output: C

Example 3: Nested conditionals for multi-criteria validation

<code class="language-cpp">#include <iostream>

<p>int main() {</p>
<p>    int age = 22;</p>
<p>    int height = 172;</p>
<p>    if (age >= 18) {</p>
<p>        if (height >= 170) {</p>
<p>            std::cout << "Adult and tall enough";</p>
<p>        } else {</p>
<p>            std::cout << "Adult but not tall enough";</p>
<p>        }</p>
<p>    } else {</p>
<p>        std::cout << "Not an adult";</p>
<p>    }</p>
<p>    return 0;</p>
<p>}</code>

Output: Adult and tall enough

Critical best practices:

Always use braces {} for blocks—even single-line blocks—to prevent ambiguity
else if chains are evaluated sequentially; the first true condition triggers execution
Avoid deep nesting by restructuring logic (e.g., using else if chains over multiple if statements)
Never omit break in switch (we’ll cover this in the next section)

The if / else construct is your go-to for flexible decision-making. Master it, and you’ll write code that adapts to complex real-world scenarios. 🚀

switch

The switch statement provides an elegant alternative to chained if / else when comparing a single expression against multiple discrete values. It’s especially efficient for handling integer, enum, or character-based cases.

Here’s the standard syntax:

<code class="language-cpp">switch (expression) {
<p>    case value1:</p>
<p>        // Code for value1</p>
<p>        break;</p>
<p>    case value2:</p>
<p>        // Code for value2</p>
<p>        break;</p>
<p>    ...</p>
<p>    default:</p>
<p>        // Code for no matches</p>
<p>}</code>

Example 1: Simple grade-to-score conversion

<code class="language-cpp">#include <iostream>

<p>int main() {</p>
<p>    char grade = 'B';</p>
<p>    int score = 0;</p>
<p>    switch (grade) {</p>
<p>        case 'A':</p>
<p>            score = 90;</p>
<p>            break;</p>
<p>        case 'B':</p>
<p>            score = 80;</p>
<p>            break;</p>
<p>        case 'C':</p>
<p>            score = 70;</p>
<p>            break;</p>
<p>        default:</p>
<p>            score = 0;</p>
<p>    }</p>
<p>    std::cout << "Score: " << score;</p>
<p>    return 0;</p>
<p>}</code>

Output: Score: 80

Example 2: Day-of-week mapping

<code class="language-cpp">#include <iostream>

<p>int main() {</p>
<p>    int day = 3;</p>
<p>    std::string dayName;</p>
<p>    switch (day) {</p>
<p>        case 1:</p>
<p>            dayName = "Monday";</p>
<p>            break;</p>
<p>        case 2:</p>
<p>            dayName = "Tuesday";</p>
<p>            break;</p>
<p>        case 3:</p>
<p>            dayName = "Wednesday";</p>
<p>            break;</p>
<p>        default:</p>
<p>            dayName = "Other";</p>
<p>    }</p>
<p>    std::cout << "Day: " << dayName;</p>
<p>    return 0;</p>
<p>}</code>

Output: Day: Wednesday

Key behaviors to understand:

The expression must be an integer, enum, or character (C++17+ supports std::string via explicit conversion)
Always include break after each case to prevent “fall-through” (execution continuing to the next case)
The default case executes when no case matches
No break = fall-through (a common pitfall):

<code class="language-cpp">  switch (day) {</p>
<p>      case 1: std::cout << "Mon"; // No break</p>
<p>      case 2: std::cout << "Tue"; // This runs too!</p>
<p>  }</code>

Output: Monto

if / else vs. switch: When to use which

Feature	`if / else`	`switch`
Best use case	Complex conditions, string comparisons	Discrete integer/enum/char values
Expression type	Any boolean expression	Integer, enum, or char (C++17+)
Case handling	One condition per block	Multiple discrete values with `case` labels
Readability	High for simple logic	Higher for value-based decisions
Common pitfalls	Deep nesting, complex boolean expressions	Fall-through without `break`

Pro tip: Use switch for:

Converting enums to strings
Mapping discrete codes to actions
Handling integer inputs with limited valid ranges

Avoid switch for:

String comparisons (use if / else or std::string methods)
Complex boolean logic (use if / else)

Summary

You now have two powerful tools for conditional logic in C++:

if / else: For flexible, complex decision-making
switch: For efficient handling of discrete values

Master these constructs by:

Using braces for all blocks
Adding break in every switch case
Choosing switch for discrete values and if / else for complex conditions

These patterns ensure your code remains readable, maintainable, and robust. Remember: the right tool for the job makes your logic both efficient and intuitive. 🔁