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All operations on values of type Real are approximations, the accuracy of which is defined by the implementation (machine) that you are using. Real is the only simple type that is not an ordinal type. Real values have no ordinal numbers, and for any real value there is no successor or predecessor value. 

As long as at least one of the operands is of type Real (the other possibly being of type Integer) the following operators yield a real value: 

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These predeclared functions accept a real argument and yield a real result: 

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These predeclared functions accept a real or integer argument and yield a real result: 

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Warning: Although real is included as a simple type, it cannot always be used in the same context as the other simple types (i.e., ordinal types). In particular, the functions pred and succ cannot take real arguments; and values of type Real cannot be used when indexing arrays, nor in controlling for statements, nor for defining the base type of a set. Furthermore reals cannot be used in a subrange type nor to index a case statement. 

