Conditional operators in C++

• Conditional operators in programming are used to make decisions based on specified conditions
• Types of conditional operators include if/else and switch

Conditional Statements in C++

• Example if/else statement with a = 10:

if (condition)
  cout << "Hello";
else
  cout << "Hi";

• If the condition in the above example is true, "Hello" is printed; otherwise, "Hi" is printed
• Another if/else example:

#include <iostream>
using namespace std;

int main() {
  int age;
  cout << "Enter The age:";
  cin >> age;
  if (age < 18) {
    cout << "You Are not Eligible." << endl;
  } else {
    cout << "You Are Eligible" << endl;
  }
  return 0;
}

• Another if/else example using total marks

if (total_marks >= 50) {
  if (condition)
    cout << "Pass";
  else
    cout << "Fail";
}

• The above code checks if total_marks >= 50 to decide whether to print 'Pass' or 'Fail' based on the inner condition

Notes and Shortcuts

• If the first condition in an if statement is true, the second else block will not be considered
• Ctrl + Shift + A creates a new file
• Ctrl + Mouse Wheel adjusts font size
• Alt + Shift + A opens the source file
• endl or \n is used to print a new line in the output

System Pause in Visual Studio

• To pause the screen after running code, use:

system("pause");

• This should be written before return 0;

Grading System Example:

• In C++, you can use if-else-if conditions to perform different actions based on the grade
• Example of grading system in Visual Studio:

#include <iostream>
using namespace std;

int main() {
  int marks;
  cout << "Enter The marks:";
  cin >> marks;
  if (marks >= 90 && marks <= 100) {
    cout << "A+" << endl;
  } else if (marks >= 80 && marks <= 89) {
    cout << "A-" << endl;
  } else if (marks >= 70 && marks <= 79) {
    cout << "B+" << endl;
  } else if (marks >= 60 && marks <= 69) {
    cout << "C+" << endl;
  } else if (marks >= 50 && marks <= 59) {
    cout << "D" << endl;
  } else {
    cout << "FAIL" << endl;
  }
  return 0;
}

Additional Notes on Conditional Statements

• Here’s a simple example to determine a grade:

Total_marks = 50;
grade;
{
  if (grade >= 90 && grade <= 100)
    cout << "A+";
  else if (grade >= 85 && grade <= 89)
    cout << "A";
  else if (grade >= 78 && grade <= 84)
    cout << "B+";
  else
    cout << "Fail";
}

• Do not use a semi-colon ; at the end of a condition
• The else block executes only when all other conditions fail
• To assign a character value, use single quotes: char variable = 'c';
• To check if the character is a lowercase alphabet, use this code: if (var >= 'a' && var <= 'z') cout << "small alphabet";
• Numbers are called ASCII

Conditional Statements in C++

• Includes: if statement, if-else statement, Nested if, if-else-if statement, and switch statement

If Statement in C++

• Used to execute code when a condition is true, also known as a one-way selection statement
• Syntax

if (condition) {
  Statement(s);
}

• Example

#include <iostream>
using namespace std;

int main() {
  int a, b;
  a = 50;
  b = 50;
  if (a == b) cout << "a is equal to b" << endl;
  return 0;
}

• Curly brackets can be skipped if there is only one statement in if or else, but enclose multiple statements within curly brackets

If-else statement in C++

• Used to execute code if a condition is true or false, also called two-way selection statement
• Syntax

if (condition) {
  Statement(s1);
} else {
  Statement(s2);
}

Nested if statement in C++

• An if statement inside another if statement forms a nested if statement
• Structure

if (condition_1) {
  Statement1(s);
  if (condition_2) {
    Statement2(s);
  }
}

• Statement1 executes if condition_1 is true
• Statement2 executes only if both condition_1 and condition_2 are true

If-else-if Statement in C++

• Used for checking multiple conditions with one "if" and one "else"
• Syntax

if (condition_1) {
  /*if condition_1 is true execute this*/
  statement(s1);
} else if (condition_2) {
  /* execute this if condition_1 is not met and condition_2 is met */
  statement(s);
} else if (condition_3) {
  /* execute this if condition_1 & condition_2 are not met and condition_3 is met */
  statement(s);
} else {
  /* if none of the condition is true then these statements gets executed */
  statement(s);
}

Switch statement

• C++ switch...case switch (n) { case constant1: // code to be executed if n is equal to constant1; break; case constant2: // code to be executed if n is equal to constant2; break; default: // code to be executed if n doesn't match any constant}
• Example : Program to Check Number is Even or Odd

#include <iostream>
using namespace std;
int main() {
  int n;
  cout << "Enter an integer: ";
  cin >> n;
  if (n % 2 == 0)
    cout << n << " is even.";
  else
    cout << n << " is odd.";
  return 0;
}

Example: C++ Program to Find All Roots of a Quadratic Equation

#include <iostream>
#include <cmath>
using namespace std;
int main() {
  float a, b, c, x1, x2, D;
  cout << "Enter coefficients a, b and c: ";
  cin >> a >> b >> c;
  D = b * b - 4 * a * c;
  if (D > 0) {
    x1 = (-b + sqrt(D)) / (2 * a);  // sqrt() library function is used to find
                                     // the square root of a number
    x2 = (-b - sqrt(D)) / (2 * a);
    cout << "Roots are real and different." << endl;
    cout << "x1 = " << x1 << endl;
    cout << "x2 = " << x2 << endl;
  } else if (D == 0) {
    cout << "Roots are real and same." << endl;
    x1 = (-b) / (2 * a);
    cout << "x1 = x2 =" << x1 << endl;
  } else {
    cout << "Roots are complex and different." << endl;
  }
  return 0;
}

Program to find Maximum

#include <iostream>
using namespace std;
int main() {
  cout << "Insert two numbers to find the maximum one\n";
  cout << "----------------------------------------\n";
  double FNum, SNum;
  cout << "First Number= ";
  cin >> FNum;
  cout << "Second Number= ";
  cin >> SNum;
  cout << "----------------------------------------\n";
  if (FNum > SNum)
    cout << "First Number= " << FNum << " Is the maximum Number\n";
  else if (FNum < SNum)
    cout << "Second Number= " << SNum << " Is the maximum Number\n";
  else
    cout << "First Number = Second Number";
  return 0;
}

Program to find largest Number among three Numbers

#include <iostream>
using namespace std;
int main() {
  float n1, n2, n3;
  cout << "Enter three numbers: ";
  cin >> n1 >> n2 >> n3;
  if ((n1 >= n2) && (n1 >= n3))
    cout << "Largest number: " << n1;
  else if ((n2 >= n1) && (n2 >= n3))
    cout << "Largest number: " << n2;
  else
    cout << "Largest number: " << n3;
  return 0;
}

Loops in C++

• Used to repeat a specific block until an end condition is met
• Types of loops: for loop, while loop, do...while loop

For Loop

• Syntax

for (initialization Statement(counter); testExpression; updateStatement) {
  // code
}

• Works as follows:
  • The initialization statement is executed only once at the beginning
  • The test expression is evaluated. If the test expression is false, the for loop is terminated
  • And if the test expression is true, codes inside body of for loop is executed and update expression is updated
  • The test expression is evaluated again, and this process repeats until the test expression is false

While Loop

• Syntax

while (testExpression) {
  // codes
}

• Works as follows:
  • The while loop evaluates the test expression
  • If the test expression is true, codes inside the body of while loop is evaluated
  • Then, the test expression is evaluated again. This process goes on until the test expression is false
  • When the test expression is false, the while loop is terminated

do...while Loop

• Has one important difference, the body of the loop is executed before the test expression is checked
• Syntax

do {
  // codes;
} while (testExpression);

• Works as follows:
  • Codes inside the body of loop executes at least once
  • The test expression is then checked
  • If the test expression is true, the body of loop is executed then the process repeats
  • When the test expression is false, the do...while loop is terminated
• Example C++ program to add numbers until the user enters 0:

#include <iostream>
using namespace std;

int main() {
  float number, sum = 0.0;
  do {
    cout << "Enter a number: ";
    cin >> number;
    sum += number;
  } while (number != 0.0);
  cout << "Total sum = " << sum;
    return 0;
}

Other Code Examples:

• C++ Program to Calculate Sum of Natural Numbers

#include <iostream>
using namespace std;

int main() {
  int n, sum = 0;
  cout << "Enter a positive integer: ";
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    sum += i;
  }
  cout << "Sum = " << sum;
    return 0;
}