Some More C++

8/2/2019 Some More C++

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Some More C++

Explicit Casting, some more

operators, Conditions, Loops

Engineer Jokhio Sultan Salahuddin Kohistani

Lecturer, CSE, MUET Jamshoro

Session - II



Explicit Casting

Conversion with force or forceful conversion orconversation with brutality.

Using static_cast keyword.

Syntax

data-type var-name = static_cast<data-type> (value);

The data-type at both sides must be same, in order forconversion to take place.



Explicit Casting 1

#include<iostream>using namespace std;

int main(){

float z = static_cast<float>(1)/2;

cout<<z;return 0;

}



Explicit Casting 2

#include<iostream>using namespace std;

int main(){

int asciiCode = static_cast<int>('A');

cout<<asciiCode;return 0;

}

This program will show the ascii code of the

given character.



Task

Write the program which can input roots for a quadraticequation (a,b,c) and solve the equation for that roots andfind out the solution.

= − ±

− 42



Solution#include<iostream>

#include<cmath>using namespace std;

int main(){

float a, b, c;

double psX, ngX;

cout<<"Enter value of A";cin>>a;cout<<"Enter value of B";cin>>b;

cout<<"Enter value of C";cin>>c;

psX = ((-1 * b)+sqrt(b*b-4*a*c))/(2*a);

ngX = ((-1 * b)-sqrt(b*b-4*a*c))/(2*a);

cout<<"Positive roots are "<<psX<<" and negativeroots are "<<ngX;

return 0;

}



Operators

These entities perform some kind of operations over theoperands.

Three Categories

Arithmetic (+, -, *, /, %, op operators, unary increment

decrement) Logical (&&, ||, !)

Relational (>, <, >=, <=, ==, !=)



Relational Operators

These type of operators compare two values.

Value can be built-in data types.

Comparison is performed in terms of higher, lower, equal toetc. etc.

These are :

They return some Boolean value (1, 0 or true, false) as resultof comparison

Operator Purpose

== Checks for equality

> Checks is greater than

< Checks is lower than

>= Checks is greater than or equal to

<= Checks is lower than or equal to

!= Checks for inequality




cout<<5>3; //returns 1 int a = 5;

int z = 2;

cout<<a<z; //returns 0

Results

on nextslide






A common mistake!

People get confused in Assignment Operator (=) &

Equality Relational Operator (==)

Assignment is only used to assign values to the variable atleft hand side.

While, Equality Relational Operator is used to comparetwo values for equality.

1==2; //return what??

int a;

a = 2; //is

a==2; // different from above a=2.



Program// relat.cpp

// demonstrates relational operators

#include <iostream>

using namespace std;

int main()

{int numb;

cout << “Enter a number: ”;

cin >> numb;

cout << “numb<10 is “ << (numb < 10) << endl;

cout << “numb>10 is “ << (numb > 10) << endl; cout << “numb==10 is “ << (numb == 10) << endl;

return 0;

}



Loops

Loops are used to repeat/iterate statements.



Loops

Loops are one of basic features of programming, whichallows an statement or a group of statements to beexecuted multiple times, depending on the condition.

Loop continues to execute statements, while the

condition remains true. When condition becomes false,loop ends and stops.

There are three kinds of loops, For Loop, While Loop, Doloop or Do-While Loop.

All are used with different situations.



The for Loop

Used when the exact number of iterations/repetitions areknown.

Used in case, we know in advance that how much numberof times, statements need to execute.

To use for loop, we have “for” (without quotes) C++keyword.

Its one of easiest loops, as all loop elements arecontained in place, in one peace.

Syntax on the next slide.



for loop syntax

for (initialization expression; testexpression; increment expression)

single statement;

for (initialization expression; testexpression; increment expression){

statement;

statement;

statement;}

If Single Statement is needs to looped.

In case of Multiple Statements, enclosethem into pair of curly braces to form acode block.



Program

// fordemo.cpp

// demonstrates simple FOR loop

#include <iostream>


int main()

{int j; //define a loop variable

for(j=0; j<15; j++) //loop from 0 to 14,

cout << j * j << “ “; //displaying thesquare of j

cout << endl;

return 0;

}



for Loop syntax



for Loop Operation

Have a look at the fordemo.cpp once again.



Some for loops variations

for (int z = 100;z>=1;z--); //loop from100 to 1 with step of -1.

for (int i = 5;i<=100;i+=5); //loop

from 5 to 100 with step of +5.

for (int i = -100; i<101;i++); //loopfrom -100 to 100 with step +1



Table Program#include<iostream>


int main(){

int a;

cout<<"Input any number, and i will generate its table\n";

cin>>a;cout<<"Upto which extent table must be generated?\n";

int z;

cin>>z;

cout<<'\n';

for (int i = 1; i<=z; i++)

cout<<a<<'*'<<i<<'='<<a*i<<'\n';

return 0;

}



Factorial Program// factor.cpp

// calculates factorials, demonstrates FOR loop

#include <iostream>


int main()

{

int numb;

long fact=1L; //long for larger numbers

cout << “Enter a number: “;

cin >> numb; //get number

for(int j=numb; j>0; j--) //multiply 1 by

fact *= j; //numb, numb-1, ..., 2, 1

cout << “Factorial is “ << fact << endl;

return 0;

}



Nested for Loop

Nested : one inside other. for loops are also used inside arrays to access different

array elements. *

One for loop can be nested inside the other one.

for each single step of the outer loop, inner for loop willcomplete its all iterations.

Nested for loops have a lot of applications, they aremostly used to access elements in multidimensional

arrays.*



Program

#include<iostream>


int main(){

for (int j = 1; j<= 10; j++){

for (int i = 1; i<=5; i++)

cout<<i+i<< " ";

cout<<endl;

}

return 0;

}



Multiple Statements in for#include <iomanip> //for setw

using namespace std;int main()

{

int numb; //define loop variable

for(numb=1; numb<=10; numb++) //loop from 1 to 10

{cout << setw(4) << numb; //display 1st column

int cube = numb*numb*numb; //calculate cube

cout << setw(6) << cube << endl; //display 2ndcolumn

}return 0;

}



Variable Scope

Variable Scope is the capability of a variable to beaddressed/called.

Sometimes called variable’s visibility.

Variables some time depends on the blocks of statements

inside { }. In the previous program, cube variable is not accessible

outside the for Block. Since it is declared inside its block,so its scope is only limited to that block.



The While Loop

Used when we don’t know the exact number of repetitions to be performed in our program.

It uses “while” (without quotes) as a c++ keyword forlooping.

It continues to execute the statements associated with it,if the condition is true, if suddenly condition become false,it will not execute the statements, and will jump to thosestatements, which are just below, outside the loop body.



While Syntax

for single statementwhile (condition or test expression)

Statement;

for multiple statementswhile (condition or test expression)

{

statement(s);

}



Syntax



Program

// endon100.cpp

// demonstrates WHILE loop

#include <iostream>


int main()

{

int n;

while( n != 100 ) // loop until n is 0

cin >> n; // read a number into n

cout << endl;

return 0;

}



Explanation

Now the loop continues to ask to the user to input anumber (n) until 100 is not inputted. As this conditionwill become true, loop will stop and will execute rest of the statements.

So, As long as the test expression is true, the loopcontinues to be executed. In above, the text expression

n != 100 (n not equal to 100) is true until the user enters100.

Since there is not any pair of braces, the single cinstatement is inside the loop, while the cout statement is

just outside the loop.



Operation of the While loop



#include <iostream>

#include <iomanip> //for setw


int main(){int pow=1; //power initially 1

int numb=1; //numb goes from 1 to ???

while( pow<10000 ){ //loop while power <= 4 digits

cout << setw(2) << numb; //display numbercout << setw(5) << pow << endl; //display fourth

power

++numb; //get ready for next power

pow = numb*numb*numb*numb; //calculate fourth power

}

cout << endl;

return 0;

}



The Fibonacci Series

Write a Program which can print the Fibonacci series.

In the next program we are using unsigned keyword infront data types, which will enforce the compiler toconsider only the positive values, while the negative willbe omitted.

Also depicts the precedence between Relational and Arithmetic

operators.



#include <iostream>


int main()

{

const unsigned long limit = 4294967295;//largest long

unsigned long next=0; //next-to-last term

unsigned long last=1; //last term

while( next < limit / 2 )

{

cout << last << “ “; //display last term

long sum = next + last; //add last two terms

next = last; //variables move forward

last = sum; // in the series}

cout << endl;

return 0;

}



Precedence between relational and

arithmetic operators

You might be thinking of placing the arithmetic operationinside the pair of Parenthesis i.e. next<(limit / 2)

to enforce the arithmetic operation to take place priorthan the relational one, but that is not the story at all,because compiler automatically thinks of the precedence,since according to language specifications, arithmeticoperators have the higher precedence than relationaloperators, so they would be evaluated first and thenresult is operated with relational operator.



The Output



The do loop (or do-while loop)

The do loop is a bit different from the other ones.

Unlike while loop, which places the condition at top, doloop places condition at last, at also checks conditionafter executing the statements.

The do loop, despite of having true or false condition,executes the loop statements at least once, and thenchecks the condition, if then condition is false, it will exitthe loop, if it is still true, the do loop will again execute

the statement until the condition is not becoming false. It uses “do” (without quotes) keyword, and “while”

(without quotes) keyword as well



The do loop Syntax

In case of single statement.

dostatement;

while (condition);

In case of multiple statements.

do {statement;

statement;}

while (condition);

#include <iostream>




int main(){

long dividend, divisor; char ch;

do

{

cout<<“Enter dividend : “; cin>>dividend;

cout <<“Enter divisor: “; cin>>divisor;

cout<< “Quotient is “<< dividend / divisor;

cout <<“, remainder is “<< dividend % divisor;

cout <<“\nDo another? (y/n): “; //do it again?

cin>>ch;

}

while( ch != ‘n’ ); //loop condition

return 0;

}



Explanation

Initially loop statements are executed and then conditionch != ‘n’ is checked, now if the user have entered n, then

condition will become false, and loop will stop, but if theuser continues to enter some other character, thecondition will remain true, and loop will execute thestatements once again. This will continue, up till the userdoes not enter n from the keyboard.

Output



Syntax



Operation of the do loop



Decision Making Statements

Decision Making is a controlling mechanism.

Sometimes, in daily life we make decisions based onspecific situations and conditions, Similarly in computerprogramming decisions are also made on certain

conditions. We have many structures for implementing the decision

making in C++.

If Structure, If- else, switch-case structures are used for

decision making problems.



The If and If-Else structure.

Every Decision is based on some condition.

If structure is used to take decision based on thecondition, if condition is true, decision is taken andstatement(s) associated with it are executed.

If is simplest decision making structure. Sometimes it is combined with else keyword to provide

the facility of alternative decision.



Program

// ifdemo.cpp

// demonstrates IF statement#include <iostream>


int main()

{int x;

cout << “Enter a number: “;

cin >> x;

if( x > 100 )

cout << “That number is greater than 100\n”;

return 0;

}



Syntax



Operation of the If Loop



If with else: Syntax



If-else operation



#include <iostream>

using namespace std;int main()

{

int x;

cout << “\nEnter a number: “;

cin >> x;if( x > 100 )

cout << “That number is greater than 100\n”;

else

cout << “That number is not greater than

100\n”; return 0;

}



prime number program#include <iostream>


#include <process.h> //for exit()

int main() {

unsigned long n, j;

cout <<“Enter a number: “; cin >> n;

If(n<1){cout<<“Invalid Number:”;exit(0);}

for(j=2; j <= n/2; j++) //divide by every integer from

if(n%j == 0) {

cout<<“It’s not prime; divisible by “<<j<<endl;

exit(0);}

cout << “It’s prime\n”;

return 0;

}



process.h and exit() function & explanation

exit(0), zero inside parenthesis, is used to suddenly stop the

execution of the program at any place, since it is contained insideprocess.h header file, we also need to include it inside our

program.

In this example the user enters a number that is assigned to n.

The program then uses a for loop to divide n by all the numbersfrom 2 up to n/2. The divisor is j, the loop variable. If any value of jdivides evenly into n, then n is not prime. When a number dividesevenly into another, the remainder is 0; we use the remainderoperator % in the if statement to test for this condition with

each value of j. If the number is not prime, we tell the user andwe exit from the program. Here’s output of the program:

Enter a number: 13

It’s prime



The getch() and getche() Functions

To use getch() or getche() we must include conio.h header

file as #include<conio.h>

The getch() and getche() ask the user to press some keyfrom the keyboard or they simply for a character input.

They provide means for holding the screen, in case user isdirectly executing the program without entering the DOS.

The difference b/w getch() and getche() is that getche() asksthe user to enter a character and also allows echoes

(displays on the screen) entered character as soon as it in

typed, while getch() only asks the character to be inputted.

both can save a character in a variable.



Program

#include<iostream>

#include<conio.h>


int main(){

char z1 = 'H';cout<<z1<<'\n';

getche();

getch();return 0;

}



The Switch-Case Statement

Provides alternative way in case we have a large if-elsedecision tree.

If you have a large decision tree based on single variableas if-else conditions, you can use the switch-case clause

more conveniently. Switch-Case structure works in cases of single variable’s

possible varying value.



Syntax



Operation



So, where ever switch’s case is matched, that particular

block is executed and break keyword forces the controlto move outside the block of the code.

If no any case is matched, then the code inside default:keyword is executed and switch-case is finished.

According to standard convention, default must be placedat last of the switch case block.



Example#include<iostream>


int main(){

char englishLetterA;

cout<<“Enter A:”;cin>>englishLetterA;

switch(englishLetterA){

case ‘A’:

cout<<“Capital A”;break;

case ‘a’:

cout<<“small a”;break;

default:cout<<“Invalid Input not A or a”; break;

}

return 0;

}



Task

Write a program, which asks the user to input an englishalphabet letter, and determines whether it is consonantor a vowel (using switch-case operators).



Logical Operators

These operators allow you to combine the Booleanvalues (which could be result of a relational operation ora Boolean data type’s value), and they also produce

Boolean (true / false) value as a result.

Three operators;

AND (&&)

OR (||)

NOT (!)



Logical operators#include<iostream>


int main(){

int num1, num2, num3;

cout<<"enter three decimal numbers\n";

cin>>num1>>num2>>num3;if(num1>num2 && num1>num3)cout<<num1<<" is largest\n";

if(num2>num1 && num2>num3)cout<<num2<<" is largest\n";

if(num3>num1 && num3>num2)cout<<num3<<" is largest\n";

if (num1==num2 || num1==num3 || num2==num3)

cout<<"All "<<num1<<"'s are equal";

return 0;

}



The End of Session - II

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