Basic C/C++ concepts example: Temperature Conversion
Prof. Reed

Example # 1: minimal essentials, output, semi-colon, comments( /* */), newline

Example # 2: variables, input, expressions, comments (//), arithmetic, precedence

Example # 3: if statement, assignment (=), indentation, blocks {}, exit( -1), sanity checks

Example # 4: looping, C style input (scanf) and output (printf), display format size(e.g. %4d)

Example # 1: minimal essentials, output, semi-colon, comments( /* */), newline

/*
   This program simply shows an output line only
  
   Author: Charles Babbage Jr. 
   System: C++ on Sun network, g++ compiler
   Date: 1/1/02
   Input: None
   Output: A one line message
 */

#include 
using namespace std;
       
int main() 
{ 
   cout<< "Hello everyone!\n";
   return 0;
} 

Example # 2: variables, input, expressions, comments (//), arithmetic, precedence

/* 
   This program converts Fahrenheit to Celsius.
 
   Author: Dale Reed
   System: C++ on UIC Sun network, g++ compiler
   Date: 8/26/2002
   Input: Fahrenheit temperature
   Output: Equivalent Celsius temperature
   Sample run:
       Please enter the Fahrenheit temperature: 85
       85 fahrenheit is 29.4444 celsius.
 */

#include 
using namespace std;

main()
{
   int fahrenheit, celsius;             //Declare the variables used
        
   cout<< "Please enter the Fahrenheit temperature: ";	//Prompt
   cin>> fahrenheit;			 	//Read in fahrenheit

   // Compute and display result
   cout<< fahrenheit 
       << " fahrenheit is " 
       << (fahrenheit - 32) * 5.0/9.0 
       << " celsius." 
       << endl;
}

Example # 3: if statement, assignment (=), indentation, blocks {}, exit( -1), sanity checks

/*
 *  This program converts either way between Fahrenheit and Celsius.
 *
 *  Author: Dale Reed
 *  System: C on UIC Sun network, g++ compiler
 *  Date: 1/1/96
 *  Input: 1 for F.-> C., 2 for C.-> F., and the source temperature
 *  Output: Equivalent temperature in either C. or F.
 */
 
#include 
#include 
using namespace std;

main()
{
   // Variable declaration section
   int sourceTemperature, answer, menuChoice;    
        
   cout<< "\nPlease choose one of the following:\n";
   cout<< "   1. Farenheit to Celsius\n";
   cout<< "   2. Celsius to Farenheit\n";
   cout<< "   3. Exit from program\n";
   cout<< "Your choice: ";
   cin>> menuChoice;       // Read in the desired menu choice
   
   // Process menu option
   if (menuChoice == 3) {     // If menu choice was 3, exit from program
      exit( 0);               // normal program termination
   }
   if (menuChoice > 3) {		// Abort on invalid menu options
      cout<< "*** Invalid menu option entered.***   Aborting...\n";
      exit( -1);              // Abnormal program termination
   }
          
   //Prompt for temperature
   cout<< "Please enter the source temperature: ";
   cin>> sourceTemperature;
   
   // Calculate correct answer depending on menu selection
   if (menuChoice == 1) {		 	//F. to C.
      answer = (sourceTemperature - 32) * 5.0/9.0;
   }
   else if (menuChoice == 2)  {     	// C. to F.		
      answer = sourceTemperature * 9.0/5.0 + 32;
   }	
   else {		// This should never be executed!
      cout<< "***Sanity check failed. Invalid menuChoice***   Aborting...\n";
      exit( -1);	// leave the program
   }
          
   cout<< sourceTemperature << " converted is: " << answer << endl;   
   
   return 0;
}

Example # 4: looping, C style input (scanf) and output (printf), display format size(e.g. %4d)

/*  This program calculates temperature conversions, showing a table 
       with farenheit and celsius temperatures.    	

    Input:  Program asks for the number of rows in the temperature conversion table
    Output: Table showing Fahrenheit in increments of 20 & corresponding Celsius  
    Author: Dale Reed
    System: SUN, CC compiler
    Revision History:
        8/27/96  Updated for EECS 171 class at UIC  
    Input:  Program asks for the number of rows in the temperature conversion table
    Output: Table showing Fahrenheit in increments of 20 & corresponding Celsius 
        Running the program looks like this:

        This program gives a table showing Farenheit to Celsius 
        temperature conversions, in Fahrenheit increments of 20 degrees.
		
        Enter a value for the number of table rows (< 11): 4
        Farenheit    Celsius
             0         -17
            20          -6
            40           4
            60          15
 */
 
#include 

main()
{
    /* Variable declaration section */
    int step = 20;			/* step size */
    int fahrenheit = 0;		/* initialize fahrenheit starting value */
    int celsius = 0;		/* initialize fahrenheit starting value */
    int	rows = 0;			/* use to keep track of number of table rows */ 
    int i;					/* loop counter */

    /* Prompt for and get the counter for number of table rows */
    printf("\nThis program gives a table showing Farenheit to Celsius \n");
    printf("temperature conversions, in Fahrenheit increments of 20 degrees.\n\n");
    printf("Enter a value for the number of table rows (< 11): " ); 
    scanf("%d", &rows);    
    if ( rows > 10)   {		/* Verify number of rows is valid */
        printf("Sorry, number must be < 11.  Aborting...\n");
        exit( -1);
    }

    /* Main loop, calculating the numbers and displaying the table as we go */
    printf("Farenheit    Celsius\n");   /*display table title */
    i = 0;						/* Initialize loop counter just before it is used */
    while (i < rows) {
        celsius = (5.0/9.0) * (fahrenheit-32.0);
        /* Note that "%4d" below signifies a decimal display format in 4 spaces */
        printf("  %4d        %4d\n", fahrenheit, celsius);	
        fahrenheit = fahrenheit + step;
        i = i + 1;
    }

}