CMSC 104 - Classwork 5

cw05.c

/*
 * PART 1: Replace this section with a properly formatted header
 */
#include <stdio.h>

int main()
{
    /*******************************************************
     *
     * PART 2:
     *
     * Before making changes, compile the program. Then run it several
     * times. Notice what happens to the value printed for PART 2.
     * This is a result of using uninitialized variables. After you have
     * run the program and observed the results, add the code needed to
     * assign values to `firstOperand` and `secondOperand` such that the
     * printed sum is 24.
     */

    int firstOperand;
    int secondOperand;

    printf("*** Begin output for PART 2 *********\n");
    printf("The sum is %d\n", firstOperand + secondOperand);
    printf("*** End output for PART 2 ***********\n\n");





    /*******************************************************
     *
     * PART 3
     *
     * PART 3 has a bug. It should print the area of a rectangle with a height
     * and width as stored in the variables `rectangleHeight` and
     * `rectangleWidth`. Find the mistake and correct it.
     */

    int rectangleHeight = 3;
    int rectangleWidth = 12;

    printf("*** Begin output for PART 3 *********\n");
    printf("The area of the rectangle is %d\n", firstOperand * secondOperand);
    printf("*** End output for PART 3 ***********\n\n");




    /*******************************************************
     *
     * PART 4
     *
     * In PART 4, declare and initialize another variable of type float that
     * represents the radius of a circle. Then modify the second `printf`
     * statement to use the radius and the value stored in `pi` to print the
     * area of the corresponding circle.
     */

    float pi = 3.14159;
    // declare and initialize a variable to hold the radius value

    printf("*** Begin output for PART 4 *********\n");
    // fix the following line so that it prints the area of the circle
    // using the radius variable that you defined along with the variable
    // named `pi`. Hint: the `*` operator works with more than two operands
    // (e.g. 4 * 4 * 2)
    printf("The area of the circle is %f\n", pi);
    printf("*** End output for PART 4 ***********\n\n");




    /*******************************************************
     *
     * PART 5
     *
     * Complete the section below so that the user is prompted for the
     * diameter of a circle and the program prints the circumference.
     */

    float diameter;

    printf("*** Begin output for PART 5 *********\n");

    printf("Enter the diameter of the circle and press enter\n");
    // add code to get the diameter from the user

    // modify the next line to print the circumference of the circle. Hint:
    // you can reuse the pi variable from PART 4
    printf("The circumference of the circle is %f\n", 2);
    printf("*** End output for PART 5 ***********\n\n");




    /*******************************************************
     *
     * PART 6
     *
     * Run the program and examine the ouput for PART 6. Notice that the
     * `printf` statements are printing different values for a variable with
     * the same name. This is because variables are visible to different parts of
     * the code depending on what block the code and variables appear in. This
     * visibility of variables is called "scope". In short code can see
     * variables that are defined before that particular part of code and that
     * appear either in:
     *    a) the same block of code, or
     *    b) in a block of code containing the block in which the code appears.
     *
     * There is nothing to change in PART 6. Just read the explanations below,
     * and run the program as many times as you need in order to understand
     * what is going on. But, feel free to modify it if you think it will help
     * you understand.
     *
     */

    // this is the "outer" variable
    int part6_value1 = 20;

    printf("*** Begin output for PART 6 *********\n");

    // the following statement can see the outer variable because it follows the
    // declaration and because the declaration appears in the same block of code
    // as the statement.
    printf("Value 1, the first time: %d\n", part6_value1);

    // Note the start of an inner block of code
    {
      // the outer variable is also visible to the second `printf` statement
      // because it appears in a block of code that contains the block in which
      // the statement appears.
      printf("Value 1, the second time: %d\n", part6_value1);

      // this is the "inner" variable
      int part6_value1 = 5;

      // the third `printf` statement cannot see the outer variable. This is
      // because it appears after a declaration of the inner variable of the
      // the same name. The inner variable in this case hides, or "shadows"
      // the outer variable.
      printf("Value 1, the third time: %d\n", part6_value1);
    }

    // the fourth `printf` statement cannot see the inner variable. This is
    // because the inner variable does not appear in the same block of code
    // as the statement nor does it appear in a block of code that contains
    // the block where the statement appears. It can however see the outer
    // variable because the statement appears after the declaration and because
    // the declaration occurs in the same block as the statement.
    printf("Value 1, the fourth time: %d\n", part6_value1);

    printf("*** End output for PART 6 ***********\n\n");




    /*******************************************************
     *
     * PART 7
     *
     * Be sure you understand PART 6 first
     * 
     * Modify PART 7 by adding two `printf` statements such that the program
     * will print the value of `part7_value1` when it is 20 and the value of
     * `part7_value2` when it is 5. Do not modify the existing code in any way
     * except to add a line as needed for the additional `printf` statements.
     * Start each line with something like "The value of part7_value1 is...".
     * End each line of output with a new line.
     */

    int part7_value1 = 20;
    int part7_value2 = 15;

    {
      printf("*** Begin output for PART 7 *********\n");
      int part7_value1 = 10;
      int part7_value2 = 5;
    }
    printf("*** End output for PART 7 ***********\n\n");
}