While defining a constant there are some rules that must be followed.

for example: To define integer constant rules are:

-It must have at least one digit.

-There must be no decimal point.

-It does not allow any blanks or commas.

-An integer constant can be both negative and positive.

-We assume an integer constant to be positive if there is no sign in front of that constant.

-The allowable range for this type of constant is from -32768 to 32767.

similarly, rules exist for the string constant, real constant, character constant, floating-point constant, etc.

• And those constants which do not follow these rules are considered as invalid constants.

Ex:

‘ab’ is an invalid character constant (since char must have only one literal)

25,234 is an invalid integer constant (since is not an integer)

25 is an invalid floating-point constant (since it doesn’t contain . a period), etc.

1. Take water in 5 litre container from water supply. (5 litre container now has 5 litres and 3 litre container has 0 litres)

2. Pour water into 3 lit container from 5 litre container and empty 3 litres container. (Now 5 litre container has 2 litres and 3 litre container has 0 litres).

3. Pour the 2 litres from 5 litre container to 3 litre container. (Now 5 litre container has 0 litres and 3 litre container has 2 litres).

4. Take water in 5 litre container and pour 1 litre to 3 litre container as it already has 2 litres.

5. Now 5 litre container will have 4 litres of water.