What is control structure and how many types are ?

Control structure:

Control structure defines the flow of execution of a program.

There are following control structures:

1.      Sequential

2.      Iteration

3.      Conditional

4.      Functions

           Sequential

The sequential control structure is a type which defines that the flow of execution will in a sequence.

Here is an example to understand it

#include<iostream.h>

#include<conio.h>

void main()

{

  clrscr();

  cout << “Hello world” ;

  getch();

}

The above program is the example of sequential control structure. It means that firstly clrscr(); function will be executed and then cout<< “Hello world” ; statement will be executed and then getch(); function will be executed. It is the normal flow of the execution of a program.

           Iteration

Iteration means repetition. Iteration means repeating a block of statement instead of writing the same statement many times.

Here is an example to understand:

#include<iostream.h>

#include<conio.h>

void main()

{

            clrscr();

            int c=0;

            while(c<=5)

                        cout << “I love Pakistan” << endl ;

            getch();

}

            Output:

                        I love Pakistan

I love Pakistan

I love Pakistan

I love Pakistan

I love Pakistan

The above example is the example of iteration control structure. It will execute until value of c doesn’t reached to 5. Means it repeats cout << “I Love Pakistan” << endl ; five times.

The above output can be generated by the following program.

#include<iostream.h>

#include<conio.h>

void main()

{

  clrscr();

  cout << “I love Pakistan” << endl ;

  cout << “I love Pakistan” << endl ;

  cout << “I love Pakistan” << endl ;

  cout << “I love Pakistan” << endl ;

  cout << “I love Pakistan” << endl ;

  getch();

}

            There are the main types of loops:

1.      while loop

2.      do-while loop

3.      for loop

Later we will discuss about the types of loop in details.

            Conditional

Conditional control structure defines the flow of execution of a program in a condition.

Here is an example to understand the conditional control structure.

#include<iostream.h>

#include<conio.h>

void main()

{

  clrscr();

  int marks;

  cout<< “Enter marks: ” ;

  cin>> marks;

  if (marks > 40)

       cout<< “ Congratulation! You have passed ” ;

  getch();

}

In the above example if you input marks to 40 the output will be “Congratulation! You have passed” otherwise there will be nothing in the output of the program.

           Function:

A Function is a set of instructions which is used to perform a specific task. Every C++ program has at least one function which is main(). You can divide your program info different function depending on you.

Example:

A simple example of the function is the “clrscr();” function which is used to clear the output window.

What are operators in C++ and types of operators ?

Operators:

Operators are symbols which are used to perform arithmetic, conditional and logical operations or manipulations.

There are the following operators in C++:

1.      Arithmetic operators

2.      Comparison operators

3.      Logical operators

4.      Other operators

1.     Arithmetic operators:

Arithmetic operators are used to performing arithmetic operations such as addition, subtraction, multiplication and division.

Operator Name	Description	Operation
+	Used to add operands.	2 + 3 = 5
-	Used to subtract operands.	4 - 2 = 2
*	Used to find product of operands.	7 * 3 = 21
/	Used to perform division.	12 / 4 = 3
%	Provide the reminder of the division.	12 / 4 = 0

2.     Comparison operators:

Comparison operators compare two values or operands to check whether it is greater, less or equal.

Operator name	Description	Operation
<	Used to find the smaller value	IF( A < B ) then  TRUE
>	Used to find the greater value	IF( A > B) then TRUE
<=	Used to find less than or equal value	IF(A <= B) then TRUE
>=	Used to find greater than or equal value	IF( A >= B ) then TRUE
!=	Used to find not equal value	IF (A != B) then TRUE
==	Used to find equal value	IF ( A == B) then TRUE

3.     Logical Operators:

Logical operators are used to apply logical functions which are:

1. AND ( && )
2. OR ( || )
3.  NOT ( ! )

AND:

AND Operator works with at least two operands:

X	Y	X AND Y
0	0	0
1	0	0
0	1	0
1	1	1

It evaluates the result of two conditions if the both conditions are true otherwise false.

Here is an example to understand it:

If ((A > B) && (A > C))

            cout << A << ” is greater ”;

In the above example if the value of A is greater than B and greater than C the result will be A.

OR:

OR operator is also a logical operator which evaluates the result if one of them conditions is true

X	Y	X OR Y
0	0	0
1	0	1
0	1	1
1	1	1

Here is an example to understand it:

If ((A > B ) || ( A < C))

            cout << A << ” is greater ”;

In the above example the result will be value of “A” if A is greater than B or C.

NOT

NOT operator is the negation of the result it shows the result true if condition is false and wise versa.

X	!(X)
0	1
1	0
0	1
1	0

Here is an example to understand it:

If ( !( A > B ) )

            cout << B << ” is greater ”;

In the above example if the value of A is greater than B the NOT operator will change the result and shows that B is greater than A.

4.     Other Operators:

These are the some other operators which are also used:

·         Assignment operator

·         Compound assignment operator

·         Increment/decrement

·         Ternary operator “?”

Assignment operator:

      Assignment operator is used to assign a value to a variable.

      Int A=10;

Compound assignment operator:

Compound assignment operators are used to assign value as well as operation with value.

A+=10 à  A = A + 10;

      Increment/decrement

Increment operator increases the value of a variable by 1 and decrement decreases the value of the operator by 1

A=10;

B = ++A;	Here the value of B is 11 because firstly it is incremented by 1 and then assigned to B.
C = --A;	Here the value of C is 9 because firstly it is decremented by 1 and then assigned to C.
X = A--;	Here the value of X is 10 because firstly the value of A is assigned to X and then    decremented by 1.
Y= A++;	Here the value of Y is 10 because firstly the value of A is assigned to Y and then incremented by 1.

       Ternary operator

The ternary operator is used to evaluating a condition. It returns one value of result depends on the condition.

Condition ? “result1” : “result2” ;

If the condition is true the output will result1 otherwise result2.

Example:

A = ( 7 > 2 ) “True” : “False” ;

The value of A is true because the condition is true and output is “True”.