Flow Control

Normal code is executed from top to bottom, starting from the main function, Flow control in C and C++ refers to the mechanisms that control the sequence in which statements are executed in a program. This includes decisions, loops, and jumps, allowing the program to behave differently based on conditions or to repeat certain actions.

To change the flow you can use a number of keywords:

• if, else
• Ternary
• Switch
• while, do-while
• For
• Range-based
• Try, catch, and throw
• Jump Statements

these keywords work with logical expressions:

• (x > 0)
• (y-2 < b)

and you have to use parentheses to format the condition.

If-else

int x = 7;
if (x > 10) {
    printf("x is greater than 10\n");
} else if (x > 5) {
    printf("x is greater than 5 but less than or equal to 10\n");
} else {
    printf("x is 5 or less\n");
}

Ternary

It is a concise way to perform a simple if-else statement. It is available in both C and C++, but it’s often used more frequently in C++ due to the language’s emphasis on concise and expressive code.

// condition ? expression_if_true : expression_if_false;
int a = 10;
int b = 20; 
// Using ternary operator 
int max = (a > b) ? a : b;

int z = 15; 
// Finding the maximum value using nested ternary operators 
int max = (x > y) ? ((x > z) ? x : z) : ((y > z) ? y : z);

switch case

int in = 0;

switch(in) {
    case 0: 
        printf("Zero");
        break;
    case 1:
        printf("One");
        break;
    default:
        print("unknow");
} 

while loop

It is repeats a block of code as long as a condition is true.

while(keepgoing)
{
    // ...
    break;
    continue;
    if (answer == 0)
    {
        keepgoing = false;
    }
}

do-while

Similar to while, but the condition is checked after the loop’s body is executed, ensuring the loop runs at least once.

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

for loop

Traditional for loop has three parts:

• initialiser
• continue condition
• incremented

for (int loop = 0; loop < 10; loop++ )
{
    // ...
}

for range (C++11)

int arr[] = {1, 2, 3, 4};
for (int x : arr)
{
    cout << x ; // will print 1234
}

Jump Statements

Jump statements allow the program to abruptly change the flow of execution.

break statement

Exits a loop or switch statement prematurely.

for (int i = 0; i < 10; i++) {
    if (i == 5) {
        break;
    }
    printf("i = %d\n", i);
}

continue statement

Skips the remaining code in the current iteration of a loop and moves to the next iteration.

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

goto statement

Jumps to a labeled statement. Its use is generally discouraged as it can lead to unstructured and hard-to-read code.

int x = 5;
if (x == 5) {
    goto label;
}
printf("This won't be printed if x is 5\n");
label:
printf("Jumped to label\n");

try , catch, and throw (C++ only)

C++ provides a structured way to handle errors and exceptions using try, catch, and throw blocks.

#include 
#include 

int main() {
    try {
        int x = -1;
        if (x < 0) {
            throw std::invalid_argument("Negative value not allowed");
        }
        std::cout << "Value of x: " << x << std::endl;
    } catch (const std::exception &e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }

    return 0;
}

return statement

Exits a function and optionally returns a value.

int add(int a, int b) {
    return a + b;
}