CAD in Civil Engineering - Baustatik-Info-Server

Page 22 Computer Languages for Engineering - SS 13Because there are de facto so many special data types in FORTRAN 90 a new concept was introducedto setup the desired byte length of a data type with the so called KIND number. The KIND number isdepended of the implementation of the FORTRAN 90, that means that the byte length is not generallyknown, if the KIND number is given. The KIND number of a given value can be evaluated by the functionKIND.The following FORTRAN 90 code evaluates the KIND number of 0.0 and 0.0d0, i.e. of single and doubleprecision for the gfortran compiler on 32 bit Windows XP. 4Listing 2.4: Evaluating the Kind Number 901 ! Program to evaluate the kind number of2 ! - single precision (REAL)3 ! - double precision (DOUBLE PRECISION)4 program kinds5 write( * ,’(" Kind of single precision:",i2)’) kind(0.0) ! it’s single6 write( * ,’(" Kind of double precision:",i2)’) kind(0.0d0) ! it’s double7 end programFigure 2.1 shows the compile and execution step of the Kind application. And you can see from theoutput, that single precision gives a KIND number of 4, double precision a KIND number of 8 like real*4aund real*8 in the case FORTRAN 77 standard extension (see above).Figure 2.1: Evaluating the Kind Numbers2.5.3 Data RangesIf you select a data type for an implementation, then you should know the available data range of thatdata type. The data range can be depended of the installed operating system and from the processorhimself. So an integer of the Windows3 has half the range as the integer from WindowsXP, if the rangeis not explicit set using the * version of the data type. If a not properly data type is selected, then thecode will be inefficient if the data range is larger than needed. If the data range is smaller then needed,the code will not run properly because the data will go out of range, which will result an overflow withall it’s unpredictable consequences 5 .The following table shows the ranges of the FORTRAN 77 data types.4 You see, that in FORTRAN 90 a program starts with the key word program and ends with end program.5 If you will implement a complex calculation algorithm with a lot of operations like the triangulation of a matrix, then youshould use the double precision data types, to avoid a losses of information.)E. Baeck