2. 1 Lab-1 CSIT-121 Fall 2004 Lab Targets Solving problems on computer Programming in C++ Writing and Running Programs Programming Exercise

3. 2 Targets We wish to learn how to program in VC++ We should know how to launch Visual C++ integrated environment We should know how to compile a program Let us work on most fundamental aspects of programming in C++

4. 3 Programming Fundamentals We have a real life problem that is to be solved on the computer In order to solve it, we need to write a program The program must be written using the syntax rules of Visual C++

5. 4 Example Problem A problem is given as follows: “If a car travels 25 miles per gallon, what is its kilometer per liter rating?” Given this problem, let us first design a program that will convert miles into kilometers. Thus we can compare the MPG and KPL.

6. 5 Strategy to solve the problem How would you solve this problem with paper and pencil? (Conversion Factor 1 Mile = 1.6 KM)

7. 6 Solving through programming We will use C++ syntax to solve this problem on the computer We first need to know the total number of data items in this problem and their type TOTAL DATA ITEMS

8. 7 Solution on paper Next we should solve it on paper. The solution on paper is called an algorithm Initial Algorithm Read the MPG Convert it to Kilometers per gallon Convert gallon into liters Compute Kilometers per liter

9. 8 Refined Algorithm

10. 9 How to implement in C++? How should we implement this solution in C++? First part is to express the data in C++ C++ provides data types to capture our real life data into programs For numbers, we can have whole numbers such as 19 or FP numbers such as 19.63

11. 10 How to express numbers in C++ The Kilometers could contain fractional part because of the 1.6 conversion factor We need a data format that can accept a FP number into it C++ provides float and double double dist_km, dist_miles;

12. 11 Variables and Constants If you can change the value of a data item in your program, it is known as a variable. If you cannot change the value of a data item in your program, it is a constant. Can you change the value of the conversion factor between Miles and Kilometers? How can we show constant data items?

13. 12 Constant Data Items For constant data items, just add the keyword const before their declaration For example, const float ConversionFactor=1.6; (Please notice the “initialization” of the data item with a specific value)

14. 13 Microsoft Visual Studio Microsoft Visual Studio is a suite of development tools Launching VC++ (Start  Programs  Microsoft Visual Studio 6.0  Microsoft Visual C++ 6.0) Learn about the IDE interface of Visual C++ File  New  Files  C++ Source File

15. 14 Basic Template to Start a Program #include using namespace std; void main() { ::: }

16. 15 Template Description –#include This line tells the system to include pre- defined I/O capability so that we can use the keyboard and screen

17. 16 Template Description –void main() This line gives the name of the function that you are developing. main() is the default name used for the main function of any program Function is a block of code that performs a given task. A function carries a name and opening and closing braces

18. 17 Program Development Phase-I In phase-I, we should input our declarations of data items into the template Let us do it now:

19. 18 Basic Template to Start a Program #include using namespace std; void main() { double dist_km,dist_miles; const float ConversionFactor=1.6; } Please note the semicolons after each declaration

20. 19 Phase-II: Action part Once we store our data into data items, we are ready to perform the actual conversion from miles to kilometers First we should read the miles from the keyboard cout<<“Give the distance in miles per gallon”; cin>>dist_miles;

21. 20 PhaseII: Action part cout<< is the way to display your data on the screen cin>>variable_name is the way to read data from the keyboard and assign it to one variable in the program

22. 21 Q&A How are fractional numbers (e.g. 3/4 or 1 1/2 are represented in C++? What is the use of opening braces and closing braces in the program? What is the difference between variables and constants? What keyword is added to make a value constant? What does cin>> do? Why do we put semicolons at the end of each statement?

23. 22 Our Program so far…. #include using namespace std; void main() { double dist_km,dist_miles; const float ConversionFactor=1.6; cout<<“Give the distance in miles per gallon”; cin>>dist_miles; }

24. 23 Phase II continues Now we have read the distance in miles Next, our program should convert it into kilometers using the conversion factor It is here that we should design an “assignment statement”

25. 24 Phase II continues Here, we are multiplying the mileage by the conversion factor and getting the result as distance in km distance in km = distance in miles*1.6 This arithmetic expression can be written in C++ using an assignment statement dist_km = dist_miles*1.6

26. 25 Rules of Assignment Statement In C++, you will use the destination variable on left of the equal sign You cannot use a constant data item on left of the equal sign You should not assign a FP value to an integer variable Doing so will cause the loss of fractional part

27. 26 Programming Exercise Extend this program by adding the trip cost calculation feature. The user will enter the distance traveled in miles from the trip meter. Convert this distance into kilometers and divide by KPL (kilometers per liter ratio) to calculate the total amount of fuel consumed in liters. Multiply this quantity by 0.85 to get the total amount of money spent in fuel purchase. Add tolls and coffee as desired. Display the result.