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.