Special Programming Workshop CSIT-120 Spring 2001

Special Programming WorkshopCSIT-120 Spring 2001 • Workshop Targets • Solving problems on computer • Programming in C++ • Writing and Running Programs • Programming Exercise

Targets • We wish to learn how to program • We know how to edit a program, compile it and run it • We know how to launch Visual C++ integrated environment • Let us work on most fundamental aspects of programming in C++

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: • “Given several distances in kilometers, we wish to see the same in miles.” • Given this problem, let us first design a program that will convert only one given distance into miles. We can change it later to let it convert several given distances into miles

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

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 distance in kilometers • Convert it to miles • Display the distance in miles • Now refine this algorithm

Refined Algorithm

How to implement in C++? • The big question is how to implement this solution in C++? • First part is to express the distance value 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++? • For whole numbers, we have data type int in C++ • For example, we can declare int distancekm; • (We have declared a data item called distancekm that is a whole number) • Now, we need another data item to represent distance in miles

How to express numbers in C++ • The distance in miles could contain fractional part because conversion factor has a fractional part • We need a data format that can accept a FP number into it • C++ provides float and double • float distancemiles;

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 to show constant data items?

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)

Basic Template to Start a Program • #include <iostream.h> • void main() • { • ::: • ::: • ::: • }

Template Description • #include <iostream.h> • 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(void) • 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 put our declarations of data items into the template • Let us do it now:

Basic Template to Start a Program • #include <iostream.h> • void main() • { int distancekm; float distancemiles; const float ConversionFactor=1.6; • } • Please note the semicolons after each declaration

Phase-II: Action part • Once we capture our data into data items, we need to perform the actual conversion from kilometers to miles • First we should read the kilometers from the keyboard • cout<<“Give the distance in kilometers”; • cin>>distancekm;

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.h> • void main() • { int distancekm; float distancemiles; const float ConversionFactor=1.6; cout<<“Give the distance in kilometers”; cin>>distancekm • }

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

Phase II continues • Here, we are dividing the distance in kilometers by the conversion factor and getting the result as distance in miles • distance_in_miles = distance_in_km/1.6 • This arithmetic expression can be written in C++ using an assignment statement • distancemiles=distancekm/ConversionFactor;

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

Complete Program • #include <iostream.h> • void main() • { int distancekm; float distancemiles; const float ConversionFactor=1.6; cout<<“Give the distance in kilometers”; cin>>distancekm; distancemiles=distancekm/ConversionFactor; cout<<“Here is distance in miles”; cout<<distancemiles; }

Programming Exercise • Write a program that accepts the age and weight of your cat. Then it shows the age and weight to the user and the meows of the cat are printed as “meow meow” on the screen

Special Programming Workshop CSIT-120 Spring 2001