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Page 34 Computer Languages for Engineering - SS 13Figure 2.2: Factorial using INTEGER with 4 BytesFor larger numbers the choice of a real data type is recommended. Within a real data type only theexponent can overflow. The mantissa can not overflow, because it’s independent of the number’s size. Ifwe use the largest available data type double precision 10 , we will get the situation of figure 2.3.We see, that with the 8 byte real the factorial reaches 170!. The next result is indicated as Infinity. Thishappens, if the memory for the exponent overflows. A 4 byte real has an exponent range of −38 · · · + 38,a 8 byte real has an exponent range of −308 · · · + 308. We see, that the largest occurring exponent is+306.2.9 BranchingBranching and decisions can be implemented in Fortran like in the most languages with an if -statement.The application of if constructs will be discussed using the implementation of the general form of aquadratic equation. Within a first approach the implementation in a Fortran66 like program is shown.2.9.1 if Statement, Fortran 66 likeWithin the first standardized Fortran version, which will be compiled from modern Fortran compilerstoo, the if statement is very rough. It’s like a branch in assembler language, that is, the if statement onlyis able to process one statement. Note the two statements in the macro assembler code of section 1.2.1resumed below. Within a first step, a registers data is compared. In a second step a conditional jump isperformed.1 ...2 cmp edx, 2 < comparing the content of the edx with 23 ja @f < jump, if equal4 ...10 The data type double precision with FORTRAN 90 is obsolete, see also section 2.5.2, but can be used, if you want.E. Baeck