Introduction to Fortran Programming. - input / output -

Transcription

1 Introduction to Fortran Programming - input / output -

2 read statement Grammar read(unit numbers, Format) Input1, Input2, Substitute "UNIT numbers" into "Input target" according to "format" UNIT=* or 5 is standard input (Keyboard input). Format=* is input in standard format. 1

3 write statement Grammar write(unit number,format) Output1, Output2, Output "Output" as "Format" to "UNIT number". UNIT=* or 6 is standard output (Display output). Format=* is output in standard format. 2

4 Example 1 Declare integer types of variables i and j so that you can read values from the keyboard with read statements. Also, output the variables i and j to the terminal display with a write statement. 3

5 Example 1 program disp implicit none integer :: i, j read(*,*) Please input i and j read(*,*) i, j write(*,*) i and j are write(*,*) i, j stop end program disp 4

6 External file input / output Grammar open(unit number,option) Open the file and associate it with the Unit number Natural number representing unit number. 0, 5, and 6 can not be used. Option file = file name -> Specify the file name Unit number can be freely set from 0 to : standard error 5 : standard input 6 : standard output 5

7 External file input / output Grammar close(unit number,option) Close the file and cancel association with Unit number Unit number specifies the file opened by the open statement Start using files (open statement) File I/O (read/write statement) End using files (close statement) 6

8 Example 2 Create "kaki" file and "yomi". Please write in the "yomi" file: 1, 2 3, 4, 5 At that time, write a program that copies the contents of "yomi" file to "kaki" file. The file name should be "copy.f90". Open "yomi" and "kaki" file with open sentence. Read "yomi" file with read statement Write to "kaki" file with write statement Close "yomi" and "kaki" files with close statement 7

9 Example 2 Filename copy.f90 program copy implicit none integer :: a, b, c open(10,file='yomi') open(20,file='kaki') read(10,*) a,b write(20,*) a,b read(10,*) a,b,c write(20,*) a,b,c close(10) close(20) stop end program copy Filename yomi 1, 2 3, 4, 5 Filename kaki? 8

10 External file input / output Grammar open(unit number,option) Open the file and associate it with the Unit number Natural number representing unit number. 0, 5, and 6 can not be used. Option status = NEW OLD REPLACE SCRATH UNKOWN -> NEW : Error to open file already exists OLD : Error to open file does not exist REPLACE : Overwrite if an open file already exists. If the file does not exist, create a new one. SCRATH : Designate for temporary files UNKOWN : When unknown. If you do not write status. 9

11 External file input / output Grammar open(unit number,option) Open the file and associate it with the Unit number Natural number representing unit number. 0, 5, and 6 can not be used. Option action = READ WRITE READWRITE -> READ : Open file read-only WRITE : Open file write-only READWRITE : Open the file without limitation. If don t write Action, it will be READWRITE. 10

12 External file input / output Grammar open(unit number,option) Open the file and associate it with the Unit number Natural number representing unit number. 0, 5, and 6 can not be used. Option err = s -> If an error occurs when opening a file, it jumps to the statement number s and continues processing (error handling). Note: What is a statement number? Sentences are numbered. statement number execute statement 11

13 External file input / output program name implicit none open(10, file= kaki, status= NEW,err=1000) open(20, file= yomi, status=old,err=2000) stop 1000 write(*,*) ERROR : cannot open kaki file stop 2000 write(*,*) ERROR : cannot open yomi file stop end program name 12

14 Format statement Grammar statement number format(edit descriptor) edit descriptor Type I edit descriptor : inumber An edit descriptor for reading and writing integer variable and constant values. ##### is a space, # is a number to display. Display only the number of number after i. If the display digit is smaller than number after i, fill with space. If the display digit is larger than number after i, it can not be displayed. 13

15 Format statement Grammar statement number format(edit descriptor) edit descriptor Type I edit descriptor : inumber An edit descriptor for reading and writing integer variable and constant values. Example integer :: a = 1234 write(*,100) a write(*,200) a 100 format( a=,i3) 200 format( a=,i5) Output a=*** a= 1234 i3 : Display 3 digit number. Can not display... i5 : Display 3 digit number. Fill with space. 14

16 Format statement Grammar statement number format(edit descriptor) edit descriptor Type I edit descriptor : inumber An edit descriptor for reading and writing integer variable and constant values. Example Output integer :: a = 1234 a=*** a= 1234 write(*,100) a, a 100 format( a=,i3, a=,i5) 15

17 Format statement Grammar statement number format(edit descriptor) edit descriptor Type F edit descriptor: fnumber1.number2 An edit descriptor for reading and writing real type variables and constant values. ±###.#### Width of number2 Width of number1 : Numeric digits after the decimal point are displayed by the number2. : Numbers including space, floating, and decimal point are displayed by the number1. 16

18 Format statement Grammar statement number format(edit descriptor) edit descriptor Type F edit descriptor: fnumber1.number2 An edit descriptor for reading and writing real type variables and constant values. Example real :: a = write(*,100) a write(*,200) a 100 format( a=,f10.2) 200 format( a=, f12.4) Output a= a=

19 Format statement Grammar statement number format(edit descriptor) edit descriptor Type E edit descriptor: enumber1.number2 Edit descriptor for reading and writing real type variables and constants in exponential notation. ±0.####E±### Width of number2 Width of number1 : Numeric digits after the decimal point are displayed by the number2. : Numbers including space, floating, decimal point, and E are displayed by the number1. 18

20 Format statement Grammar statement number format(edit descriptor) edit descriptor Type E edit descriptor: enumber1.number2 Edit descriptor for reading and writing real type variables and constants in exponential notation. Example real :: a = write(*,100) a write(*,200) a 100 format( a=,e10.2) 200 format( a=, e12.4) Output a= -0.12E+02 a= E+02 19