All other combinations are permitted. These are described in detail below. Note that conversion from real to double precision cannot produce any information not present originally. This makes it especially important to provide a decimal point at the end of a real constant even if the fractional part is zero. For example dividing by zero, raising a negative value to a real power, and raising zero to a negative power.
Errors can also occur because numbers are stored on a computer with finite range and precision.
A similar effect on very large negative integers is called underflow. Most systems will issue a warning message for overflow or underflow, and may abort the program, but some processors cannot detect errors of this sort involving integer arithmetic. Note that variables and arrays are initially undefined unless a suitable DATA statement is used. All the operands in a constant expression must be literal constants or previously defined named constants. Variables, array elements, and function references are all prohibited.