Nesting of selection and iteration statements

Due to the facility of providing compound statements to be executed in selection and iteration statements, it is possible to nest one control statement within another.

Thus one could have a selection statement within a selection statement, or an iteration statement within an iteration. Or a selection within an iteration. And so on. There is no limit to the level of nesting of these control statements.

One pseudocode example is as follows:
 

if( test1 )
{
  statementA;

  if( test2 )

  statementB;

  statementC;

In the above example, if test1 is false, none of these statements will be executed. 

If test1 is true, statementA will be executed. Then if test2 is true, statementB will be executed followed by statementC. If test2 were false, then only statementA and statementC would be executed.

Another pseudocode example is as follows:

 while( test1 )

  statementA;

  if( test2 )

  statementB;

In the above example, if test1 is true, statementA will be executed. Then if test2 is true, statementB will be executed. Then the loop condition test1 will be evaluated again. For as long as test1 is true, statementA followed by the if statement will continue to be executed.

You may now wish to revisit the statement and control of execution concept map from Unit 3.