Solution of a quadratic equation

Program 8) An equation of  the form 
                       ax(square) + bx + c = 0
is known as the quadratic equation. The values of x that satisfy the equation are known as the roots of the equation. A quadratic equation has two roots which are given by the following two formulae:
             
                   root 1 = -b + sqrt(b(square) - 4ac)/ 2a
                   root 2 = -b - sqrt(b(square) - 4ac)/ 2a

A  program to evaluate these roots. The program requests the user to input the values of a, b and c and outputs root 1 and root 2.
                                     
                                 PROGRAM

#incluce  <math.h>
main( )
 {
        float a, b, c, discriminant, root1, root2 ;
        printf("Input values of a, b, and c\n") ;
        scanf("%f %f" , &a, &b, &c) ;
        discriminant = b*b - 4*a*c ;
        if (discriminant < 0)
              printf("\n\nROOTS ARE IMAGINARY\n") ;
       else
        { 
               root1 = (-b + sqrt(discriminant)) / (2.0*a) ;
               root2 = (-b - sqrt (discriminant)) / (2.0*a) ;
               printf("\n\nRoot1 = %5.2f\n\nRoot2 = %5.2f\n",
                                         root1, root2) ;
        }
    getch( ) ;
 }


Output:          Input values of a, b, and c
                      2   4 - 16
                      Root1 = 2.00
                      Root2 = -4.00
                      Input values of a, b, and c
                      1 2 3
                      ROOTS ARE IMAGINARY


The term (b(square) - 4ac) is called the discriminant. If the discriminant is less than zero, its square rots cannot be evaluated. In such cases, the roots are said to be imaginary numbers and the program outputs an appropriate message.
       

program of salesman's salary

Program 8) A computer manufacturing company has the following monthly compensation policy to their sales-persons:
    Minimum base salary                                   :   1500.00
    Bonus for every computer sold                      :     200.00
    Commission on the total monthly sales   :     2 per cent
Since the prices of computers are changing, the sales price of each computer is fixed at the beginning of every month. Make a  program to calculate a sales-person's gross salary. 

                                   PROGRAM

#define  BASE_SALAR               1500.00
#define  BONUS_RATE           200.00
#define  COMMISSION              0.02
main( )
 {
        int quantity ;
        float gross_salary, price ;
        float bonus, commission ;
        printf("Input number sold and price\n") ;
        scanf("%d %f, &quantity, &price) ;
        bonus                = BONUS_RATE * quantity ;
        commission      = COMMISSION * quantity * price ;
        gross_salary    = BASE_SALARY + bonus + commission ;
        printf("/n") ;
       printf("Bonus            = %6.2f\n" , bonus) ;
        printf("Commission  = %6.2f\n", commission) ;
        printf("Gross salary = %6.2f\n", gross_salary) ;
        getch( ) ;  
 }

Output:      Input number sold and price
                   5  20450.00
                Bonus                    = 1000.00
                Commission          = 2045.00
                Gross salary         =  4545.00

Given the base salary,bonus,and commission rate, the inputs necessary to calculate the gross salary are, the price of each computer and the number sold during the month.
 The gross salary is given by the equation
  Gross salary = base salary + (quantity * bonus rate)
                           + (quantity * price) * commission rate
     

Illustration of integer airthmetic

Program 7) This program shows the use of integer airthmetic to convert a given number of days into month and days.

                                 PROGRAM
 main( )
  {
        int months, days ;

        printf("Enter days\n") ;
        scanf("%d", &days) ;

        months = days/30 ;
        days = days % 30 ;
        printf("Months = %d Days = %d, months, days) ;
        getch( ) ;
 }     

Output:          Enter days 
                        265
                    months = 8 days = 25
                    Enter days
                       364
                    Months = 12 Days = 4
                    Enter days
                       45
                    Months = 1 days = 15  

The variables months and days are declared as integers. Therefore, the statement 
                   months = days/30;
truncates the decimal part and assigns the integer part to months. Similarly, the statement 
                  days = days%30 ;
assigns the remainder part of the divison to days. Thus the given numberof days in converted into an equivalent number of months and days and the result is printed as shown in the output.


         

Temperature conversion problem

Program 6) This program converts the given temperature in fahrenheit to celsius using the following conversion formula:
                             C = F- 32 / 1.8

                                                  PROGRAM
#define  F_LOW       0
#define  F_MAX     250
#define  STEP           25

main( )
 {
         typedef float REAL ;a
         REAL fahrenheit Celsius\n\n") ;
         while( farenheit <= F_MAX )
          {
                  celsius = (fahrenheit - 32.0) / 1.8 ;
               printf(" %5.1f %7.2f\n", fahrenheit, celsius);
                 fahrenheit = fahrenheit + STEP ;
          }
          getch() ;
 }     

Output:       Fahrenheit          Celsius
                             0.0              -17.78
                       25.0                -3.89
                       50.0               10.00
                       75.0               23.89
                     100.0               37.78
                     125.0               51.67
                     150.0               65.56
                     175.0               79.44
                     200.0               93.33
                     225.0              107.22
                     250.0              121.11

The program prints a conversion table for reading temperature in celsius, given the fahrenheit values. The minimum and maximum values and step size are defined as symbolic constants. These values can be changed by redefining the #define statements. An userdefined data types name REAL is used to declare the variables fahrenheit and celsius. The formation specifications %5.1f and %7.2 in the second printf statement produces two column output as shown. 

Calculation of average numbers

Program 5) A program to calculate the average of a set of N numbers

                                          PROGRAM
#define     N  10
main( )
 {
        int        count ;
        float     sum, average, number ;
        sum      = 0 ;
        count   = 0 ;
        while(  count < N)
         {
                    scanf("%f", &number) ;
                    sum = sum + number ;
                    count = count + 1 ;
         }
         average = sum/N ;
         printf("N = % Sum = %f", N, sum) ;
         printf(" Average = %f", average) ;
     getch() ;
 }

Output:    1
                 2.3
                 4.67
                 1.42
                 7
                 3.67
                 4.08
                 2.2
                 4.25
                 8.21
                 N = 10    Sum = 38799999   Average = 3.880 

The variable number is declared as float and therefore it can take both integer and real numbers. Since the symbolic constant N is assigned the value of 10 using the #define statement, the program accepts ten values and calculates their sum using the while loop. The variable count counts the number of values and as soon as it becomes 11, the while loop is exited and then  the average is calculated.
Notice that the actual value of sum is 38.8 but the value displayed is 38.799999. In fact, the actual value that is displayed is quite dependent on the computer system. Such as inaccuracy is due to the way the floating point numbers are internally represented inside the computer.  

interactive investment program

Program 4) This program can be converted into a more flexible interactive program using scanf.

In this case, computer requests the user to input the values of the amount to be invested,interest rate and period of investments by printing a prompt message
                  Input amount,interest rate,and period
and then waits for input values. 

                                                 Program
  
main( )
 {    
     int year, period;
     float amount, inrate, value;

     printf("Input amount, interest rate, and period\n\n);
     scanf("%f %f %d", &amount, &inrate, &period);
     printf("\n");
     year = 1

     while(year <= period)
      { 
               value = amount + inrate + amount ;
               printf("%2d Rs  %8.2f\n", year, value) ;
               amount = value ;
               year = year + 1 ;
      }
    getch();
 }


Output:    Input amount, interest rate, and period
                        1000  0.14 5
                     
                            1 Rs11400.00
                            2 Rs12996.00
                            3 Rs14815.44
                            4 Rs16889.60
                            5 Rs 19524.15
                 Input amount, interest rate, and period


                         20000  0.12 7

                            1 Rs 22400.00
                            2 Rs 25008.00
                            3 Rs 28098.56
                            4 Rs 31470.39
                            5 Rs 35246.84
                            6 Rs 39476.46
                            7 Rs 444213.63


Three variables amount,inrate,and period, the computer begins to calculate the amount at the end of each year, up to 'period' and produces output as shown in program.
Note that the sacnf functions contained three variables. In such cases, care should be exercised to see that the values entered match the order and type of the variables in the list. Any mismatch might lead to unexpected results. The compiler may not detect such errors.
          

Program 3) Use of scanf function

main( )
 {
         int number;
         
         printf("Enter an integer number\n");
         scanf("%d", &number);
      
         if(number < 100)
          printf("Your number is smaller than 100\n\n");
        else
          printf("Your number contains more than two digits\n");
       
     getch();
 }

Output: Enter an integer number
               54
             Your number is smaller than 100
             Enter an integer number
               108
             Your number contains more than two digits        

PROGRAM 2: USE OF MATH FUNCTIONS

Simple programs

SAMPLE PROGRAM 1: PRINTING A MESSAGE


main ( )

{
   printf("I see, I remember");
   getch();
} 

Output:  I see, I remember

               A program to print one line text  

PROGRAM 2: ADDING TWO NUMBERS

main()
{
  int number;
  float amount;
  number= 100;
  
  amount = 30.75 + 75.35;
  printf("%d\n",number);
  printf("%5.2f",amount);
  getch();
}

Output:  100
                106.

                  Program to add numbers 

PROGRAM 3: INTERSEST CALCULATION
Calculate the value of money at the end of each year of investment, assuming an interest rate of 11 percent and prints the year, and the corresponding amount in two columns. The output is shown for a period of 10 years with an initial investments of 5000.00. The program uses the following formula:
Value at the end year= value at start of year(1+ interest rate)

  
#define PERIOD           10
 #define PRINCIPAL     5000.00
 main()
 {
    int year;
    float amount, value, inrate;
    amount = PRINCIPAL;
    inrate = 0.11;
    year = 0;
  
    while(year <= PERIOD)
     {  printf("%2d   %8.2f\n" ,year, amount);
           value = amount + inrate * amount;
           year = year + 1;
         amount = values;
     }
  getch();
 }