Control structures

The control structures appear in both structured programming languages as well as object oriented programming languages.  The three constructs used are:

i).  Sequence: - This is when one statement is executed following another.

ii). Selection: -It involves making a choice between at least two alternative courses of action. In C++
      there are two ways of making selections.

• The if statements

Syntax

if  (condition)
      -----

else

with else being optional

• The switch statements

The following is the general format:

switch(variable|value)
{

Case value:  ;  [-----break;]

}

The switch is appropriate when a number of possible states of variable have to be evaluated at
once.

iii). Iteration: - It involves repeating a section of code, for a number of times. In C++ it is achieved in
      three ways

• for loop
• while loop
• do.....while loop.

In each case, there is a condition which allows the loop to terminate.

• The for loop:

The for loop has three principle elements:
      9  The start condition

9  The terminating condition

9  The action which takes place at the end of each iteration Syntax

for(start condition; continue condition; re-evaluation) 

{

Statement(s);

}

Example:

The following code segment outputs the squares of numbers one to ten

for(int i=1;i<=10;i++)

{

cout<<"The square of:  "<

}

• while loop

It is used to execute a block of statements an indefinite number of times, for zero or more number of times (i.e. pre-test loop).

Syntax

while  (condition)
{

Statement(s);

}

• do.....while loop

It is used to execute a block of statements an indefinite number of times, for one or more number of times and will execute at least once (i.e post-test loop).

Syntax

do

{

Statement(s);

} while  (condition);