A program can be executed in three different manners.
1.Sequentially
2.Selectively
3.Iteratively
In first one, the program get executed in the manner it is written. That i s one by one from up to down. For such kind of execution no further special construct is required.
In second case , proggram get executed according to the set of condition present in the program. And hence in this type of execution compiler may skip execution of few statements. For this kind of execution some special constructs are required, which is already present in the programming lanquage. Few of these constructs are:
1. IF statement
2. IF .. ELSE statement
3. SWITCH statement etc.
At last but not least, here compiler execute same set of statement again and again till condition remains true.
Various construct available for this is
1.FOR
2WHILE etc
