MET 50

1. MET 50 CHARACTER DATA

2. Character data We have extensively used REAL and INTEGER data types. There is also: CHARACTER data COMPLEX data LOGICAL data MET 50, FALL 2011

3. Character data COMPLEX numbers take the form: Z = X + iY where X and Y are both real numbers and i2= -1, so that i = (-1) MET 50, FALL 2011

4. Character data Z = X + iY X is called the real part of Z {denoted Re(Z)} REAL (X)  value Y is called the imaginary part of Z {denoted Im(Z)} AIMAG (X)  value MET 50, FALL 2011

5. Character data Fortran stores Z as two real numbers: X and Y When you write PRINT*,Z You get: (12.0, -9.0) MET 50, FALL 2011

6. Character data CHARACTER DATA Letters, spaces, punctuation marks Combined into something called a STRING MET 50, FALL 2011

7. Character data Written in code as follows: “STRING” or ‘STRING’ MET 50, FALL 2011

8. Character data Declared as follows: CHARACTER (n) :: string Where “n” is the length = number of characters in the string MET 50, FALL 2011

9. Character data example: CHARACTER (3) :: month Then “month” is type character with 3 elements, such as janfebmar Perhaps you want to print a table of results with the month printed at the top … see later for format! MET 50, FALL 2011

10. Character data Other ways to declare: CHARACTER (LEN=n) :: string1 CHARACTER :: string2  Length in 2nd example is assumed to be ONE!!! MET 50, FALL 2011

11. Character data Other ways to declare: CHARACTER :: stringa*10, stringb*20, stringc*25 MET 50, FALL 2011

12. Character data To specify the value of a string: CHARACTER (8) :: name name=“John Doe” Note that the space counts as a character!! CHARACTER (21) :: filename filename=“temperature_data_2005” MET 50, FALL 2011

13. Character data Formatted read/write of a string: In the FORMAT statement, use the descriptor: “An” As in: format (1x, I5, A20, F10.2) Options: “I”, “F”, “E”, and now…”A” (also “D”…last slides) MET 50, FALL 2011

14. Character data Unformatted read/write: CHARACTER (3) :: MONTH INTEGER :: NUMBER READ*,MONTH, NUMBER You might enter: “JAN” 150 MET 50, FALL 2011

15. Character data Defects of character (hahaha!) If a string is read in that is too long, it is truncated on the right. CHARACTER (6) :: DAY DAY = “WEDNESDAY” DAY is stored as WEDNES MET 50, FALL 2011

16. Character data If a string is read in that is too short, it is padded with blanks on the right. CHARACTER (12) :: DAY DAY = “WEDNESDAY” DAY is stored as “WEDNESDAY ” MET 50, FALL 2011

17. Character data Character data can be “added” !!! The operation is called: concatenation “cat” for short character :: first*5, second*6, third*11 first = ‘minor’ second = ‘ thing’ third = first // second produces… third = ‘minor thing’ MET 50, FALL 2011

18. Character data Useful??? Creation of file names inside some code… character :: first*9, second*4, third*9 character :: title*22 first = ‘data-for-’ third = ‘-smoothed’ DO YEAR = 1,10 if (year == 10) then second = ‘2010’ title = first // second // third endif ! Produces title = ‘data-for-2010-smoothed’ OPEN (15, file=‘title’) END DO MET 50, FALL 2011

19. Character data DOUBLE PRECISION data… Suppose you declare: REAL :: TEMP and later print a value with PRINT*,TEMP  a number with certain number of digits after the decimal. MET 50, FALL 2011

20. Character data Instead if you declare: DOUBLE PRECISION:: TEMP and later print a value with PRINT*,TEMP • a number with DOUBLE the number of digits after the decimal. • Double precision! MET 50, FALL 2011

21. Character data This may happen if you get some code that has run on a high-end machine (e.g., 64-bit) and you now want to run it on a cheapo workstation (e.g., 16-bit) … less resolution of numbers … less accuracy See page 230 !! MET 50, FALL 2011