🔁 C Control Flow – Master if…else, Loops, switch, break, continue

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🧲 Introduction – Managing Program Execution Paths

In C programming, control flow structures like conditions and loops give you the power to decide what happens next. Whether you want to execute code based on a condition, repeat tasks, or jump between statements, control flow is the foundation of logical programming.

🎯 In this guide, you’ll learn:

• How to use conditional statements (if, else, switch)
• The working of loops (for, while, do-while)
• Infinite and nested loop usage
• Loop control with break, continue, and goto

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📘 Topics Covered

🔢 Topic	📄 Description
🧠 C if…else Statements	Perform actions based on conditions
🎚️ C switch Statements	Multi-branch conditional logic
🔄 C Loops Overview	Looping with for, while, and do-while
♾️ C Infinite & Nested Loops	Continuous and embedded iterations
⛔ C break & continue Statements	Control the flow inside loops
🧭 C goto Statement	Jump to specific code blocks

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🧠 C if…else Statements

Use if…else to run different blocks of code based on conditions.

✅ Syntax:

if (condition) {
    // executes if condition is true
} else {
    // executes if condition is false
}

🧪 Example:

int age = 18;
if (age >= 18) {
    printf("Adult");
} else {
    printf("Minor");
}

📘 You can chain multiple conditions using else if.

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🎚️ C switch Statements (including nested)

switch is ideal for selecting among multiple options based on a single variable.

✅ Syntax:

switch (expression) {
    case value1:
        // code
        break;
    case value2:
        // code
        break;
    default:
        // fallback code
}

🧪 Example:

int day = 2;
switch (day) {
    case 1: printf("Monday"); break;
    case 2: printf("Tuesday"); break;
    default: printf("Invalid day");
}

📘 Nested switch statements allow deeper conditional logic:

switch (dept) {
    case 1:
        switch (year) {
            case 1: printf("First year"); break;
            case 2: printf("Second year"); break;
        }
        break;
}

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🔄 C Loops Overview (for, while, do-while)

Loops allow repeated execution of code blocks.

🔁 for loop:

Used when the number of iterations is known.

for (int i = 0; i < 5; i++) {
    printf("%d ", i);
}

🔁 while loop:

Condition is checked before entering the loop.

int i = 0;
while (i < 5) {
    printf("%d ", i);
    i++;
}

🔁 do-while loop:

Executes at least once, even if the condition is false.

int i = 0;
do {
    printf("%d ", i);
    i++;
} while (i < 5);

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♾️ C Infinite & Nested Loops

♾️ Infinite Loop:

Runs forever unless externally broken (used in systems programming).

while (1) {
    // endless execution
}

🔁 Nested Loop:

A loop inside another loop, commonly used for matrix or grid operations.

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 3; j++) {
        printf("%d %d\n", i, j);
    }
}

📘 Be cautious with nested loops—they can increase time complexity.

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⛔ C break & continue Statements

⛔ break:

Immediately exits the nearest loop or switch.

for (int i = 0; i < 5; i++) {
    if (i == 3) break;
    printf("%d ", i);
}

🔁 continue:

Skips the current iteration and proceeds with the next.

for (int i = 0; i < 5; i++) {
    if (i == 2) continue;
    printf("%d ", i);
}

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🧭 C goto Statement

goto provides an unconditional jump to a labeled statement.

⚠️ Syntax:

goto label;
...
label:
    // code to execute

🧪 Example:

int x = 5;
if (x < 10) goto skip;

printf("This won't print");

skip:
printf("Jumped to here");

🚨 Note: Use goto only when absolutely necessary. Prefer structured alternatives for clarity.

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📌 Summary – Recap & Next Steps

Control flow is essential for writing logic-based C programs. Whether it’s choosing between blocks (if, switch) or repeating tasks (for, while), these structures help define how and when things happen in your code.

🔍 Key Takeaways:

• if…else is great for 2–3 decision branches
• Use switch for clean multi-option comparisons
• for, while, and do-while allow structured repetition
• break exits a loop; continue skips one iteration
• Use goto with caution and only for specific low-level control
• Nested and infinite loops serve advanced programming needs

⚙️ Real-World Relevance:
Control flow statements are used in authentication systems, menu-driven programs, data processing loops, robotics, and real-time applications.

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❓ Frequently Asked Questions (FAQ)

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❓ When should I use a switch instead of if…else?
✅ Use switch when checking one variable against multiple constant values. It’s cleaner and more readable than multiple if...else if.

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❓ Can I have an infinite loop in C?
✅ Yes. Use while(1) or for(;;) for infinite loops. These are common in embedded systems and servers.

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❓ Is goto a good practice in C?
✅ It’s generally discouraged due to poor readability, but can be useful for exiting deeply nested loops in rare cases.

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❓ What’s the difference between break and continue?
✅ break exits a loop or switch; continue skips the current loop iteration.

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❓ Can if statements be nested?
✅ Yes. You can nest multiple if statements to evaluate complex conditions.

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❓ Which loop guarantees at least one execution?
✅ The do-while loop executes the body at least once before checking the condition.

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