Session-I & II CSIT-121 Spring 2006

Session-I & IICSIT-121 Spring 2006 • Session Targets • Introducing the VC++.NET • Solving problems on computer • Programming in C++ • Writing and Running Programs • Programming Exercise

Session Targets • Introducing the course and the syllabus • Introducing the textbook and its bundles • 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 • Finally, we should know how to execute a compiled program

VC++ in the VS.NET Environment • Introducing the Visual C++ .net environment • Suggested Steps to build a program quickly in Visual Studio.Net Environment: • Launch visual studio.net • Launch file-->new-->project • Click on the plus sign to the left of visual c++ to expand choices • Click on Win32 and choose Win32 console project • On the new dialog window, click on “Application Settings” • Under “additional options”, check the item “Empty Project” then click “Finish” • On the right, see the components of the project, right click on “c++ source files” • Choose “Add”, followed by “Add new item” • Choose c++ source file as the new item to be added and assign it a name • Type in the c++ code • Use Build"Build Solution" • Choose Debug Start without debugging to run it • Choose close solution to start fresh for each new program • Attempt Lesson 1-1, 1-2, 1-3, 1-4, 1-5, • (Source code is available on the course homepage)

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++

Example Problem • A problem is given as follows: • “If a car has MPG rating of 25 miles, 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.

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

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

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

Refined Algorithm

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

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 kpl, mpg, kpg;

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?

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

Basic Template to Start a Program • #include <iostream> • using namespace std; • void main() • { • ::: • ::: • ::: • }

Template Description • #include <iostream> • This line tells the system to include pre-defined I/O capability so that we can use the keyboard and screen

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

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

Basic Template to Start a Program • #include <iostream> • using namespace std; • void main() • { • double kpl,mpg, kpg; • const float CF=1.6; • } • Please note the semicolons after each declaration

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<<“How many miles does your car cover in one gallon (MPG rating from the sticker)?”; • cin>>mpg;

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

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?

Our Program so far…. • #include <iostream> • using namespace std; • void main() • { • double kpl,mpg, kpg; • const double CF=1.6; • cout<<“How many miles does your car cover in one gallon (MPG rating from the sticker)?”; • cin>>mpg; • }

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

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*CF • This arithmetic expression can be written in C++ using an assignment statement • kpg = mpg*CF

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

Programming Exercise Demo Due Jan 26 • Compile and run the program with sample data on the next slide • Extend the program to find the price of gas if the distance traveled is given by the user in miles and the price of gas is as below (per liter): • const double PPL = 0.95; • HINT: Algorithm Steps: • Convert the distance into kilometers (km) • Divide the distance by KPL rating (liters) • Multiply the result by PPL to obtain total price of gas

Sample Run • How many miles does your car cover in one gallon (MPG rating from the sticker)? • 25 • Your KPG rating is 40 • Your KPL rating is 10.58 • Now enter the distance (in miles) traveled from the trip meter • 400 • You spent a total of $57.46 on your trip

Session-I & II CSIT-121 Spring 2006