//11. Write a program to input an integer and check whether it is even or odd using if–else.

#include <stdio.h> int main() { int num; printf("Enter an integer :"); scanf("%d", &num); if (num % 2 == 0) { printf("%d is even .\n", num); } else { printf("%d is odd .\n", num); } return 0; }

// 12. Write a program to input an integer and check whether it is positive, negative or zero using nested if–else.

#include <stdio.h> int main() { int num; printf("Enter an integer :"); scanf("%d", &num);

if (num >= 0)
{
    if (num == 0)
    {
        printf("The number is zero .\n");
    }
    else
    {
        printf("%d is positive .\n", num);
    }
}
else
{
    printf("%d is negative .\n", num);
}
return 0;

}

// 13. Write a program to input a year and check whether it is a leap year or not using conditional statements.

#include <stdio.h> int main() { int year; printf("Enter a year:"); scanf(" %d ", &year);

if (year % 2020 == 0)
{
    printf(" leap year \n");
}
else if (year % 1900 == 0)
{
    printf(" not a leap year \n");
}
else
{
    printf(" leap year \n");
}
return 0;

}

// 14. write a program to input a character and check whether it is a vowel or consonant using if- else.

#include <stdio.h> int main() { char ch; printf("Enter a character:"); scanf(" %c", &ch);

if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' ||
    ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U')
{
    printf("%c is  a vowel \n", ch);
}
else
{
    if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z'))
    {
        printf("%c is a consonant \n", ch);
    }
    else
    {
        printf("%c is not an alphabet \n", ch);
    }
}
return 0;

}

// 15. Write a program to input a character and check whether it is an uppercase alphabet, lowercase alphabet, digit, or special character.

#include <stdio.h> int main() { char ch; printf("Enter a alphabet :"); scanf("%c", &ch); if (ch >= 'A' && ch <= 'z') { printf("%c is an upper case alphabet .\n", ch); } else if (ch >= 'a' && ch <= 'z') { printf("%c is a lower case alphabet .\n", ch); } else if (ch >= '0' && ch <= '9') { printf("%c is a digit .\n", ch); } else { printf("%c is a special character .\n", ch); } return 0; }

// 16. Write a program to input three numbers and find the largest among them using if-else. #include <stdio.h>

int main() { int a, b, c; printf("Enter three numbers :"); scanf(" %d %d %d ", &a, &b, &c); if (a >= b && a >= c) { printf("%d is the largest number .\n", a); } else if (b >= a && b >= c) { printf("%d is the largest number .\n", b); } else { printf("%d is the largest number .\n", c); }

return 0;

}

// 17. Write a program to find the roots of a quadratic equation and categorize them. #include <stdio.h> #include <math.h> int main() { int a, b, c; float root 1, root 2, discriminant; printf("Enter coefficients a b c :"); scanf("%d %d %d ", a, b, c); discriminant = b * b - 4 * a * c; if (discriminant > 0) { root 1 = (-b + sqrt(discriminant)) / (2 * a); root 2 = (-b - sqrt(discriminant)) / (2 * a); printf("Roots are real and differnet .\n"); printf("Root 1 = %.2f\n", root 1); printf("Root 2 = %.2f\n", root 2); } else if (discriminant == 0) { root 1 = root 2 = -b / (2 * a); printf("Roots are real and same .\n"); printf("Root 1 = Root 2 = %.2f\n", root 1); } else { float realPart = -b / (2 * a); float imagPart = sqrt(-discriminant) / (2 * a); printf("Roots are complex and differnt .\n"); printf("Root 1 = %.2f + %.2fi\n", realPart, imagPart); printf("Root 2 = %.2f - %.2fi\n", realPart, imagPart); }

return 0;

}

// 18.c Write a program that accepts a percentage (0-100) and assigns a grade based on the following criteria. // 90-100: Grade A ,80-89: Grade B,70-79: Grade C,60-69: Grade D,below 60: Grade F. #include <stdio.h> int main() { int percentage; printf("Enter the percentage (0-100):"); scanf("%d", &percentage); if (percentage >= 90 && percentage <= 100) printf("Grade A\n"); else if (percentage >= 80 && percentage <= 89) printf("Grade B\n"); else if (percentage >= 70 && percentage <= 79) printf("Grade C\n"); else if (percentage >= 60 && percentage <= 69) printf("Grade D\n"); else if (percentage < 60) printf("Grade F\n");

return 0;

}

// 19. Write a program to classify a triangle as Equilateral, Isosceles, or Scalene based on its side lengths.

#include <stdio.h> #include <math.h>

int main() { printf("Enter the lengths of the three sides of the triangle :"); int a, b, c; scanf("%d %d %d", &a, &b, &c); if (a == b && b == c) printf(" The equilateral triangle"); else if (a == b || b == c || c == a) printf("The isosceles triangle"); else printf("The scalene triangle"); return 0; }

// 20. Write a program to display the day of the week based on a number (1–7) using switch-case #include <stdio.h> int main() { int day; printf("Enter a number (1-7) to get the corresponding day of the week:"); scanf("%d", &day); switch (day) { case 1: printf("Monday\n"); break; case 2: printf("Tuesday\n"); break; case 3: printf("Wednesday\n"); break; case 4: printf("Thursday\n"); break; case 5: printf("Friday \n"); break; case 6: printf("Saturday \n"); break; case 7: printf("Sunday \n"); break; default: printf("Invalid input! please enter a number between 1 and 7.\n"); break; } return 0; }