CAD in Civil Engineering - Baustatik-Info-Server

Page 20 Computer Languages for Engineering - SS 13with 4 bytes. With the development of the 64 bit operating systems also 8 byte integers are available.Especially this is necessary to access to large files with a size larger then 2 GB or to be able to handlememory blocks with a size above 2 GB. On Windows32 with some provider depending tricks this wasalready possible, but according to a standard it was not till 64 bit systems are available.For floats general two formats are available, a 4 byte real and a 8 byte real. In the case of complexcalculations as solving a linear equation system it is strongly recommended to use the 8 byte float.Within the following table data types are listed with there specific properties.Type Size RestrictionINTEGER 2 Bytes Range −2 15 · · · 2 15 − 1 = 32767INTEGER 4 Bytes Range −2 31 · · · 2 31 − 1 = 2147483647 ≈ 2.14 · 10 9INTEGER 8 Bytes Range −2 63 · · · 2 63 − 1 = 9, 22 · 10 18REAL 4 Bytes Exponent range −38 · · · 38, 7 digits precisionREAL 8 Bytes Exponent range −308 · · · 308, 15 digits precisionCHARACTER 1 Byteone byte characterTable 2.2: General Data Types with their Restrictions2.4.1 Negative NumbersNegative numbers can be represented by complements of the positive number. Each digit of then positivenumber and it’s complement gives the maximum value of the digit. This would be 1 within thebinary system. Table 2.3shows the scheme for the construction of a negative number for 7 using theb-complement.Comments0000|0111 2 07 16 , the positive number has the value 71111|1000 2 FA 16 , number complement of 7, 1 -digit+ 1 2 b-complement = complement +11111|1001 2 b-complement or negative numberCheck of the b-complement to be the searched negative number0000|0111 2 positive number+ 1111|1001 2 b-complement or negative number1|0000|0000 2 The overflowing bit will be truncated and therefor the sum vanishes.Table 2.3: Construction of a negative Number2.5 Data Types, Variables and ConstantsWithin the following section we will discuss the available data types for the variables of FORTRAN 77and FORTRAN 90 and above. We will discuss how to declare and initialize variables and constants.E. Baeck