OOP :o :o :p (What is OOP , Why we want it)

     Hello Fellow Readers..  Welcome to inspire++ :) This post is specially for the people who are doing OOP now. Don't get confuse with this post , because we are still on the VARIABLES in our fundamental programming post series. OOP is a big set of lessons, so we have to do this also as a post series. This series will be continue parallel to our fundamental post series. OK... that being said..
Lets start..  

     When you have to create a big program , I mean really really big one , big enough to call it a software , we will have to do more and more coding. Sometimes we will have to re-type the same set of code-lines again and again. 

     This seems to be a big head-aching situation. So, as smart engineers what are the options do we have to do to reduce the time for coding and to reduce the pain occur when doing the same thing again and again.? 

     Well you might have the answer already. "C n P" or AKA Copy and Paste Method Right!! You type the set of code , copy it and paste wherever you want them to be in your source code. Easy!! 

     BUT!! it is not a wise method to follow for some Reasons. Imagine if there is an error or a Bug in your code , when you copy that set of codes to 20 different places in your source code , you will have the same error in 20 times and you will have to fix it 20 times repeatedly.  And imagine how your source code will look like. It will be very very long and it'll be really hard to keep working with .

1. Duplicate code is a Bad Thing.
2. More codes - Hard to work with. 

     So there is a big problem that haven't answered properly. Purpose of this post is to tell you how to solve this problem by introducing you the Concept of OOP-Object Oriented Programming. By the end of this post you will have an idea about what is OOP and Why we want it.

     Can you remember the lesson functions..Well in our Fundamental post series we haven't arrived that point yet, but I guess you guys have the idea of what is a function and how to use it..

     So in short, A function is a set of codes in your source code with a given name. It exist parallel to our main function. It does not do anything until we call it. Whenever we want we simply call the function in main function. 
     
     So instead of typing or copying the same set of code again and again in main function , we can create a function and call it when we want to execute them. This method is call function calling. So if there is any error in our code we only have to fix it in the function and whole program will fixed automatically. No need to fix same error 20 different places. 

     This concept is very helpful when understanding OOP. In software developing we use a developed version of this concept. Instead of using functions we use Classes and Objects  in OOP (Object Oriented Programming.) 

     By using Classes & Objects We Can,

1.      Reduce duplicating codes.
2.      Reduce the number of code lines in your main       function.

     And the whole program will become a User friendly neat and logical thing and it will be easy to work with. OK I think now you have an idea about why we want OOP right!!

     In OOP we create Classes - AKA the blueprints of the objects - Classes have Properties and Behaviors. And we create Objects (Real world things) using codes, and to make those objects feel real we encapsulate them, use inheritance and polymorphism to use them in advance. So as a terminology you can refer those red color words , those words will be the topics of our next posts. So stay with inspire++ to get a fully understand about OOP. Thank you guys..!! C U.. :) 
Next post>>>

Lesson no : 2 - ( COUT function & Escape Sequence )

            Hello… People with Happy Faces.. Just right after finishing the Exams and having a Leisure time.. :)

            How you doing guys.. Having fun..!! I know.. Batch trips , Vacation etc,etc.. Well… me too.. :)

           We had to pause our C++ programming post series because I had semester exams for almost an entire month from 24th of May to 17th of June.. And You know what.. the exam was my B'day gift from KDU.. Yeah people.. It was on my Birthday.. 24th of May.. Yey.. Happy birth day for me..!! :)

           However I put some posts to discuss the model papers before the exam..

            So.. Now we have enough time to continue our amazing post series ;) Let’s start again..

             Last time we ended our post with explaining the cout in c++. 

Cout is use to display or print anything on console.

You can print 

• any text 
• any value of a variable 
• result of any operations with variables 

            Remember the last time, we printed your name and your address..?? This time lets discuss some techniques we can use to print text using cout. ( By print I meant displaying it on the console. Not actually printing it using a printer!!)

             When you print texts or words using cout, you can’t print some characters as output.

• “ - double quotes 
• ‘ – single quotes
• \ - backward slash
• ? – question marks

For example

Cout<<”Don’t come late. Did you miss the bus today? ”;

            If you try to print this you will probably end up in a error. Reason is that you have ? question mark and ‘ single quote to print.

            Now you have a problem , how to print “” or ? ‘ these.. Right..? Well, you have a way to do this. It is called "escape sequence" .

You can type any of those symbols right after a backward slash, then there will be no error.

Ex:-
cout<<” Don\’t come Late. Did you miss the bus today\? ”;

Cout<<” \”Here Im Using Double quotes with in double quotes.. ;)\” ”;



Here's a list of Escape Sequence.

Try this list in your code.

Specially this \t – tab and \b-backspace part.

Ok.. I will Stop this little post from here by leaving you some exercises. Please do these and I promise you to discuss them in my next post..



Ex 01: 

                **
               ****
              ******
             ********
            **********
           ************

Write a program to print above triangle.



Ex 02:

Try to print letters like this in the terminal.



P.S

     My Fellow readers. Thanks for staying with the blog. Now You can follow my blog by subscribing, using your email address. You can see it on top of the right side-bar. And please don’t be hesitate to ask any question about anything. See  you in my next post… Let's talk about variables in next post.. 
Next Post >>>

Answers for the First Semester Exam

            Hey there.. Folks.. I'm Back after 1st sem exams.. Back in Action... ;) But, Still I can't take my mind out of the exams.. So I decided to do a post about  the exam paper.. Hope this will important to my blog readers.. :)

           This paper was included with 4 questions, and had to answer all of them. Lets start from the first one.

Q1.

a.) This is a theoretical question about programming. I copied       this answer-phrase from my previous post.

Types of Programming Errors. 

• Syntax Error
• This happens when we type incorrect codes, (ex: Missing Semi Colon ; , misspell a variable name, forget to close a Bracket  } ,  )These programs can not compile, it shows an error message.
• Logical Error.
• This error occur due to our misunderstanding of the programming logic,These programs compile without producing any error messages, but does something totally different other than what we expected from the program.(To get a total, instead of addition + we type multiplication * , this doesn't give any error message, but give an unwanted result.)  
• Runtime Error. 
• Programs with this error also compile without any error message until some error occur in runtime.
• Ex :- Devide by zero in runtime.

b.)

        (i)   Syntax Error

        (ii)  Logical Error

        (iii) Runtime Error

c.)

        (i) This statement is 'True' because in any program                      language the codes are executed line by line, so 

             without the declaration-part reads first, the program

             doesn't know what is the variable is.

        (ii) This is 'False' because, c++ is case sensitive. The                  variable name value with lower case letters and

             the variable name VALUE with upper case letters

             are not identical in c++, means both variables can be              exist at the same time.

        (iii) This is also 'True' because when 2 integers are                       divided there might be a remainder for that                             division. If any two of decimal numbers are divided

              (Floats) the answer is also a decimal point number,

              there won't be any remainder for that division.

d.)

            In this program there are 3 inputs, and we want to find the largest one only. so what we do is, we compare two numbers first and get the largest from those two and compare that with the other remaining number.(we need not to find the order of numbers , just the largest one only) To do that we need three selection conditions, one input and three output diagrams.

 Q2.

a.)

            In this question what you have to do is create some names for some variables they have given, using the rules and etiquette we have taught. 

(i)   float speed , float Speed , float spd ,.. etc.

(ii)  char Grade , char grade , char grades , char Grades ,              char Grad...etc

(iii)  float selPrice , float sel_price ,...etc

b.) 

(i)   int sum ; 

(ii)  count = 0 ;

(iii)  cout<<" The average is: "<<avg ;

       or

       cout<<"\" The average is: \" "<<avg ;

c.)

(i)  False- Even without the default case the switch works             without producing any error, but in most cases default is

      very essential part of the switch.

(ii)  False - Precedence of arithmetic operators are higher.

      Here's the order of precedence of operators.

(iii)  True- because || operator is the Logical OR operator.

d.)

Q3.

a.)

(i) while loop

    do while loop

     for loop

(ii) The while loop and the for loop are both entry-condition          loops. The test condition is checked before each iteration        of the loop, so it is possible for the statements in the loop        to never execute. 

     Exit-condition loop, in which the condition is checked after      each iteration of the loop, guaranteeing that statements          are executed at least once. This variety is called a do               while loop

(b)  

  (i)   2  1.5  1  0.5

  (ii)   10

          7

          4

          1

(iii)   10

(c)

Q4.

a.)

(i)   score

(ii)  double

(iii)  10

b.)

            A function has 2 main parts, Function Header and Function Body. As the features of a function we can consider few parts in detail, 

• return type ex:- int , static , void , float, double
• function name ex:-  int main ()  , double func1  ()
• parameter list ex:- int func1 (int num1, int num2)
• function body : rest of the function in curly braces

c.)

(i)   int   smallest   (int x,int y,int z)

(ii)  void  instructions  ()

(iii)  double  intToDouble  (int number)

d.)  

            In above function the parameters(arguments) in function header x and y are declared with ampersands. int &x , int &y.This is because we want to pass the value to the function by reference.

            That means when the values of the arguments are changed in the function, actual values of the reference variables are also changed. 

Here I attached the complete program for you to try.

#include <iostream>

using namespace std;

void zeroSmaller(int &x, int &y);

int main ()

{

   

   int a;

   int b;

 cout<<"Enter a value for  a"<<endl;

 cin>>a;

cout<<"Enter a value for  b"<<endl;

 cin>>b;

   zeroSmaller(a, b);

   cout << "After  value of a :" << a << endl;

   cout << "After  value of b :" << b << endl;

   return 0;

}

void zeroSmaller(int &x, int &y)

{

  if(x>y)

  {

      y=0;

  }

  else{x=0;}

   return;

}

            Here in function zeroSmaller, if x is lower then x will be set to zero by the function , but at the same time the actual value of a is also set to zero, because the value was passed by reference. And the value of b will be set to zero if the y is the lowest.

            So that's all for the first semester exam. Hang around with my c++ programming posts series to learn this completely from the beginning.  

            If you have anything to be more explained please mention in comments section below or any good or bad thoughts about this blog please comment.

See you in my next post.. Happy vacation.. :)

Quick Post For 1st Semester Exam

Hey Guys.. This is a Quick Post to Discuss About the Model Paper of my Uni.. hope others will get something from this too..

Here I pasted the paper...  And Down there I Discussed it...

Question 01                                                                                                                (25 Marks)

(a)    Differentiate the machine language and the high level language.                  (5 Marks)

(b)   Define the terms compiler and interpreter.                                                     (5 Marks)

(c)    Describe the different ways to include comments in a C++ source code. State whether the comments are nested.                                                                                     (5 Marks)

(d)   List the three main kinds of program errors.                                      

                                i.            Identify the error discovered, if you “misspell a variable or a function name”.

                              ii.            Identify the error discovered, if you “use a single equal sign to check equality”.

(5 Marks)

(e)    Write a C++ program to display the following output.                                  (5 Marks)

(Hint: Use escape sequences.)

            

Question 02                                                                                                          (25 Marks)

(a)    The following identifiers are written in C++ and some of them are syntactically incorrect. Identify the syntactically incorrect identifier(s) and state the reason.      (5 * 1 = 5 Marks)

                                i.            CASE4

                              ii.            2010IncomeTax

                            iii.            sales$

                            iv.            exchange Rate

                              v.            cout

(b)   Write C++ expressions for the following mathematical formula.             (5 Marks)

                    

(c)    Determine the value of each of the following expressions, if x = 5, y = 10 and z = -6. Write your steps clearly.                                                                   (5 Marks)

                                i.            y > 15 && z < x + y

                              ii.            ! ( y <= 12 ) || x % 2 == 0

(d)   Illustrate the outputs of the following program segments.                       (5 * 2 = 10 Marks)

                                i.           

int num1, num2, sum; num1 = 5; num2 = 4; sum = num1 + num2; cout << "The sum of "; cout.width(2); cout << num1 << " and " << num2; cout << "is" << sum << "\n";

float value1, value2, product; value1 = 5.31; value2 = 7.8; product = value1 * value2; cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2); cout << "The Product of\n" << value1 << "and"; cout << value2 << "is\n" << setw(14) << product;

 

                              ii.             

                                                                                               

Question 03                                                                                                                (25 Marks)

You are required to implement a program to handle customer sales of a fruits stall at Katubedda Super Market. Write a program in C++ to calculate the amount of price and print a bill for the customer. Your program should allow:

(a)    To input a number of items bought (quantity) and the price per item (unit price).                                                                                                                                         (5 Marks)

(b)   Calculate the total cost; give discount to the customer according to the following conditions.                                                                                                       (5 Marks)

If the customer bill amount is greater than Rs.500/=, will be having a 2.5% discount.

If the customer bill amount is greater than Rs.750/=, will be having a 3% discount.

If the customer bill amount is greater than Rs.1000/=, will be having a 5% discount.

(c)    Your program should ask for the amount of money tendered and print the correct amount of money change.                                                                                                                                 (5 Marks)         

(d)   Print an appropriate bill. The output should correct to two decimal places.   (5 Marks)

(e)    Your program should allow doing the calculation as many times as the user wishes.

(Hint: Use suitable C++ loop structure to implement this task.)        (5 Marks)                              

Question 04                                                                                                                (25 Marks)

A competition is being organized by StarCricket Club to select the most popular player for year 2015. Nalaka, Amila, Saman, Ruwan and Chathura are five players who are contesting for popularity. The players are numbered from 1 to 5 and voting is done by entering the player number as an input.

Write a C++ program to read the vote and to count the votes cast for each player using an array. In case, a number read is outside the range (1..5), the vote should be considered as a ‘spoilt vote’.

Your program should include the following tasks.

(a)    Define an array called “vote” to store votes of players. Initialized each array element into zero.                                                                                                                (5 Marks)

(b)   Read data into an array called “vote”. (Nalaka’s votes are in the first element of the array, Amila’s votes are in the second element of the array etc..)                               (5 Marks)

(Hint: Use switch statement to handle the user selection.)

(c)    Your program should allow 100 club members to cast their votes.                      (5 Marks)

(Hint: Use a suitable C++ loop structure to implement this task.)                            

(d)   Calculate the number of votes cast for each player, number of spoilt votes and total number of votes.                                                                                                       (5 Marks)

(e)    Print the number of votes cast for each player, number of spoilt votes and total number of votes.                                                                                                              (5 Marks)

END OF PAPER

Q1. 

a.) Difference between Machine Language and a high level         language is , 

• A machine Language is a low level language which a computer can understand or computer's use machine language to work. ex:- Assembly

• On the Other hand a high Level Language is a programming language closer to human language or as humans high level languages are easy to understand and to work-with for us.  ex:- java , c++

b.) Define compiler and Interpreter..

• compiler and interpreter both work as translators of a source code to a machine language.
• it means it translate the code we type using codeblocks into machine language.(like binary )
• Some Programming languages use compiler only i.e C, C++, some use interpreter i.e Python, Ruby, some use both.

c.)

• Compilers Translate the entire source code at once into machine code file, and then we can run our program any time we want. Compilers are Faster. Consume more memory. If there is any error in the code compilers are less accurate in finding them.
• Interpreters on the other hand  translate the code line by line , consume more time, memory efficient, and accurate in finding errors in the code.

c.) Comments in C++,

• Comments are  lines of text we put in a code which does not effect to the code any how. We use comments to mention important things in a code. We can write anything as comments there are no limits.
• There are two types of comments in C++, Single line comments and Multi line comments.
• For Single line comments we put   //  , two backward slashes and we type the comment text in a single line.
• 
  
•  For multi line comments we put   /*  at the begining of the comment and we end the comment with    */ 
• Nesting comments means put multi line comment in side another multi line comment. C++ does not support Nested comments. 
• we can check that by 
• int nest = /*/*/0*/**/1;
• cout<<nest;
• if the output is 1 , it supports nested comments and if output  is 0 then it doesn't support.

d.) Types of Errors in c++

• Compile Error  (Syntax Error)
• This happens when we type incorrect codes, (ex: Missing Semi Colon ; , misspell a variable name, forget to close a Bracket  } ,  )These programs can not compile, it shows an error message.
• Logical Error.
• This error occur due to our misunderstanding of the programming logic,These programs compile without producing any error messages, but does something totally different other than what we expected from the program.(To get a total, instead of addition + we type multiplication * , this doesn't give any error message, but give an unwanted result.)  
• Runtime Error. 
• Programs with this error also compile without any error message until some error occur in runtime.
• Ex :- Devide by zero in runtime.

1. Syntax Error (Compile Error)
2. Logical Error.

Q2.

a.) Identifiers are the names we use when programming , (Names we use to name Variables , function , class etc..) An identifier starts with a letter A to Z or a to z or an underscore (_) followed by

zero or more letters, underscores, and digits (0 to 9).

Identifiers can't have !@#$%^&*()+=.. Only Underscore.

CASE4

2010IncomeTax

sales$      // $ Dollar Sign

exchange Rate   //  Space between two words

cout  // cout is a function name, cant use as an identifier

b.)

c.)

  && - Logic AND    % - Modulas (Remainder of a devision)

   || - Logic OR        == - is equal to ??

  ! - Logic NOT

1. 
   

  i)

    = 10>15 &&    -6<15

     = false    &&    true     

      = false

ii)

       =  !(10 <= 12)   || 5%2 == 0

       =  !true  ||  false

       =  NOT (true)   OR  false

       =   false 

d.)

     i)

       

ii)

Q3.

a.) Here I posted some Screen Shots from My Code. Some code parts have described with in comments. 

(1)

(2)

(3)

(4)

Q4.

 a.)

Here also I explained every part of codes in comments, in this example I have used an if else if statement to find the winner, which has not asked to do in question paper.

(1)

(2)

(3)

(4)

That's all guys... Hope this will help you.. C..U after the exams.. Good luck.. :)