The next statement, is an instruction for the computer to read two string values the user has entered on the keyboard, the first into s1 and the second into s2. Computing with integers and doubles . Review integer and floating point accuracy. Thus it is possible to generate an integer too large to fit into the space provided. This is called overflow.
Doubles have a more complex situation.
First they are stored as a mantissa and an exponent , in a manner similar to that used in scientific notation. Doubles are stored in the machine also as a mantissa and an exponent. Again because both of these fields in the 64 bit space reserved for doubles are of limited space, it is possible that the space reserved for either the mantissa or the exponent is not large enough for the number. The exponent is limited to 10 bits or about 1000 different values. The amount of space set aside for the mantissa determines the number of significant digits or the precision with which the number can be stored.