Introduction to Computing

1
Introduction to Computing

• Formatted Input / Output

2
I / O

• There are two types of Input and Output
• statements
• list-directed free-format, extra spaces
• programmer-formatted
• Format effects only the display of variables not
  their values through program execution
• A format can specify both the horizontal and
  vertical positions of the variables on the paper
  and also significant digits to be printed.

3
Formatted Output

• print format-specifier , output-list
• write (, format-specifier) output-list
• format-specifier is one of the following
• an asterisk, - indicates list-directed
  output in which the format for the expressions in
  the output-list is machine dependent
• a character string that consists of format
  descriptors, seperated by commas and enclosed in
  parantheses
• (list of format descriptors) or
• (list of format descriptors)

4
Formatted Output

• print format-specifier , output-list
• write (, format-specifier) output-list
• label of a format statement - an integer in the
  range 1 through 99999
• each execution of a print or write statement
  displays the values of the items in the
  output-list on a new line
• Do not forget to use commas to seperate variable
  from its neighbors

5
Formatted Output

• format statement can be written in several ways

1- Write(,100) i,x 100 Format(1x,I6,F10.2)
2- character(len20) string string(1x,I6,F10.2
) Write(, string) i,x
3- Write(, 1x,I6,F10.2) i,x
6
Formatted Output

• For some Fortran compilers, the first character
  of each line of output directed to a printer is
  used to control the vertical spacing.
• blanck Normal spacing advance to the next
  line before printing
• 0 Double spacing skip one line before
  printing
• 1 Advance to top of next page before
  printing
• Overprint the last line printed

7
Format descriptors

• There are many format descriptors that may be
  used in format specifiers - a most commonly used
  list is presented in the following tables
• Forms Use
• rIw rIw.m Integer data
• rFw.d Real data in decimal notation
• rEw.d Real data in exponential notation
• rA rAw Character data
• rLw Logical data

8
Format descriptors - more

• Forms Use
• ESw.d ESw.dEe Real data in scientific notation
• ENw.d ENw.dEe Real data in engineering notation
• x x x x Character strings
• nX Horizontal spacing
• / Vertical spacing

9
Format descriptors

• Here
• w a positive integer specifying field width
• m minimum number of digits to be
  read/displayed
• d number of digits to the right of the decimal
  point
• e number of digits in an exponent
• n number of spaces to skip
• x a character
• r repeated count
• c column number

10
Integer output - I descriptor

• right-justified - each value is displayed so
  that its last digit appears in the rightmost
  position of the field of a specified size
• rIw rIw.m
• example
• integer Number 3, L 5378, Kappa -12345
• Write(,(1X, 2I5, I7, I10)) , Number, Number
  -3, L, Kappa
• Write(,(1X, 2I5.5, I7, I10.7)), Number, Number
  -3, L, Kappa
• Write(, (1X, 2I5.0, I7, I10)) , Number, Number
  -3, L, Kappa

11
Integer output - I descriptor

• example
• print 30, Number, Number -3, L, Kappa
• print 31, Number, Number -3, L, Kappa
• print 32, Number, Number -3, L, Kappa
• 30 format (1X, 2I5, I7, I10)
• 31 format (1X, 2I5.2, I7, I10.7)
• 32 format (1X, 2I5.0, I7, I10)
• will produce the following output (where _
  denotes a blank)
• _ _ _ _ _ 3 _ _ _ _ 0 _ _ _ 5378 _ _ _ _ -12345
• _ _ _ _ 0 3 _ _ _ 0 0 _ _ _ 5378 _ _ - 0 012345
• _ _ _ _ _ 3 _ _ _ _ _ _ _ _ 5378 _ _ _ _ -12345

12
Integer output - I descriptor

• if an integer value (including the minus sign)
  requires more space than specified by a
  descriptor, the field is filled with asterisks
• print (1X, 4I3) , Number, Number - 3, L,
  Kappa
• will produce
• _ _ _ 3 _ _ 0

13
Real output - F, E, ES and EN descriptors

• - real outputs are right-justified in their
  fields
• - sometimes numbers migt be rounded off in
  display
• rFw.d
• integer In 625, Out -19
• real A 7.5, B 0.182, C 625.327
• Write(,44), In, Out, A, B, C
• 44 format (1X, 2I4, 2F6.3, F8.3)
• will produce the following output
• _ _ 6 2 5 _ - 1 9 _ 7 . 5 0 0 _ 0 . 1 8 2 _ 6 2
  5 . 3 2 7

14
Real output - F descriptor

• for Fw.d descriptor
• w ? d 3
• to allow space for the sign of the number,
• a first digit,
• and a decimal point

15
Real output - E descriptor
rEw.d Real data in exp. Notation the real
variables are normalized to a range betw. 0.1 to
1.0 when displayed in exponential notation with
E.

• real A0.12345E8, B0.0237, C4.6E-12,
  D-76.1684E12
• print (1X, 2E15.5, E15.4, E14.4), A, B, C, D
• will produce the following output
• _ _ _ _ _0.12345E08_ _ _ _0.23700E-01_ _ _ _
  _0.4600E-11_ _ _-0.7617E14

16
Real output - E descriptor

• for Ew.d descriptor
• w ? d 7
• to allow a space for the sign of the number,
• a leading zero,
• a decimal point,
• and E with the exponent

17
Real output - ES and EN descriptors

• ES - scientific descriptor used in the same
  manner as the E descriptor, but the values are
  normalized so that the mantissa is at least 1 but
  less than 10 (unless the value is zero) (ESw.d)
• EN - engineering descriptor used in the same
  manner as the E descriptor, but exponent is
  constrained to be a multiple of 3 so that a
  nonzero mantissa is greater than or equal to 1
  and less than 1000. (ENw.d)

18
Character output

• rAw
• character data may be displayed by including
  them in a list of descriptors of a format
  specifier
• example
• real A 0.3, B 7.9
• print (1X, A , F6.2, B , F6.2), A, B
• or
• print 70, A, B
• 70 format (1X, A , F6.2, B , F6.2)
• will produce the following output
• _ A _ _ 0 . 3 0 B _ _ 7 . 9 0

19
Character output

• rAw
• character data may be displayed by including
  them in a list of descriptors of a format
  specifier
• Note
• if width is longer than the variable length the
  variable will be printed out right justified in
  the field
• Otherwise, only the first w characters will be
  printed out in display

20
Character output

• example
• print (1X, A, F6.2, A, F6.2), A, A, B, B
• or
• print (1X, 2 (A, F6.2) ), A, A, B, B
• also 2F6.2 is equivalent to F6.2, F6.2

21

• example
• character (len17) stringthis is a string.
• write (,75) string
• write (,76) string
• write (,77) string
• t h i s i s a s t r i n g .
• 75 format(1x,A) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
  _ _ _ _ 5 10
  15 20
• t h i s i s
  a s t r i n g .
• 76 format(1x,A20) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
  _ _ _ _ _ 5 10
  15 20
• t h i s i
• 77 format(1x,A6) _ _ _ _ _ _ _ _ _ _ _ _ _ _
  _ _ _ _ _ _ 5 10
  15 20

22
Logical output

• rLw
• output is T or F
• Example
• logicalout.TRUE. , b.FALSE.
• Write(,22) out,b
• 22 format(1x,2L5)
• _ _ _ _ T _ _ _ _ F

23
Positional descriptors - X and T

• X inserts spaces between variables
• T inserts tabs over a specific column
• nX, Tc
• example
• integer Number 141
• write(,75) John_Q. _ Doe, ABCD, Number
• 75 format (1X, A11, T16, A4, 2X, I3)
• will produce the following output
• _ John_Q. _ Doe _ _ _ A B C D _ _ 141

24
Changing Output Lines - /

• To skip lines / operator is used
• example
• integer i10
• real time 300., depth330.,amp850.65,ph
  ase30.
• write(,76) i, time,depth,amp,phase
• 76 format (1X, T20,Results for test number ,
  I3,///,
• 1x, Time, F7.0,
• 1x, Depth, F7.1,meters,/,
• 1x, Amp , F8.2,/,
• 1x, Phase, F7.1)
• will produce the following output

25
Formatted input

• READ format-specifier , input-list
• integer input
• integer I, J, K
• read (I6, I4, I7), I, J, K
• or
• read 5, I, J, K
• 5 format (I6, I4, I7)
• if the data entered is
• _ _ - 1 2 3 _ _ 4 5 _ _ _ 6 7 8 9
• the values assigned to I, J and K are
• I - 123 J 45 K 6789

26
Formatted input

• READ format-specifier , input-list
• real input
• enter the numbers without decimal points
• example (A6.25, B-1.9, C75.0, D.182,
  E625.327)
• read (F3.2, 2F3.1, F3.3, F6.3), A, B, C, D, E
• enter data in the following form
• 625-19750182625327
• enter the decimal point as part of the input
  value
• read (4F5.0, F8.0), A, B, C, D, E
• enter the data in the following form
• _6.25_-1.9_ _75._.182_625.327

27
Character input

• the line of data
• Fourscore_and_seven_years_ago
• is read by statements
• character(6) Speech1, Speech2
• read (2A) , Speech1, Speech2
• values assigned to Speech1 and Speech2 are
• Speech1 Foursc
• Speech2 ore_an

28
Character input

• Note
• if the width w is larger , the data from the
  right-most portion of the field is loaded into
  character variable.
• if the width w is smaller , the charactersin the
  field will be stored in the left-most characters
  of the variable and the remainder will be blank.

Example Character(len10)
29
Character input
Example Character(len10)string1,string2 Charac
ter(len5)string3 Character(len15)string4,str
ing5 Read(,(A)) string1 Read(,(A10))
string2 Read(,(A10)) string3 Read(,(A10)) s
tring4 Read(,(A)) string5
input ABCDEFGHIJKLMNO Ouput String1
ABCDEFGHIJ String2 ABCDEFGHIJ String3
FGHIJ String4 ABCDEFGHIJ_____ String5ABCDEF
GHIJKLMNO
30
Horizontal Positioning
X skip over fields T jump to column number. it
can read same data twice
Example Character(len6) string Integerin Re
ad(,(I6,T1,A6)) in,string
input 123456 Output in 123456 String
123456
31
Vertical Positioning
/ descriptor serves to skip new lines
input 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Outp
ut a 1.0 b 2.0 c 7.0 d 8.0
Example real a,b,c,d Read(,66) a,b,c,d 66
format(2f10.2,//, 2f10.2)
32
write statement

• write (control-list) output-list
• control-list items
• unit specifier - integer expression whose value
  designates
• the output device (or an asterisk, indicate the
  standard
• output device, monitor screen or printer)
• UNIT unit-specifier or unit-specifier
• format specifier - any of the forms allowed in
  the print
• statement
• FMT format-specifier or format-specifier

33
write statement

• write (control-list) output-list
• control-list items (continued)
• ADVANCE clause
• ADVANCE character-expression
• where the value of character-expression is
  either NO or YES
• any other items that are especially useful in
  file processing

34
read statement

• read (control-list) output-list
• control-list items
• unit specifier
• format specifier
• advance clause
• iostat clause - to detect input error or
  end-of-file condition
• examples
• read (5, ) a, b, c
• read (unit5, fmt ) a, b, c
• read (in, ) a, b, c where in has a value of 5

35
File processing

• opening files
• open (open-list)
• open list includes
• unit specifier - unit number.
• file clause - character-expression indicating
  the name of file
• status clause - character-expression with a
  value of OLD or NEW or REPLACE etc.
• action clause - i-o-action with a character
  expression of value READ or WRITE or
  READWRITE (default)

36
File processing

• position clause - character-expression with a
  value of REWIND (file at initial point)
• APPEND (file at the end)
• ASIS (position unchanged)
• iostat status-variable - an integer variable
  to which zero is assigned if the file is opened
  successfully and a positive value is assigned
  otherwise.

37
File processing

• example
• open (unit 12, File INFO.DAT, status
  OLD,
• action READ, position REWIND,
• iostat OpenStatus)
• OpenStatus is an integer variable.

38
Opening files

• Character (12) FileName
• write (unit, (1X, A), advance NO) Enter
  data file name
• read (unit, fmt) FileName
• open (unit 12, file FileName, status OLD,
  
• action read,
• position rewind, iostat OpenStatus)
• ! if file is successfully opened, OpenStatus will
  be set to 0
• if (OpenStatus gt 0) stop cannot open file
  

39
Closing files

• Close (close-list)
• where close-list must include a unit specifier
  and may include other items such as iostat, err
  and status

40
File input/output iostat

• During read and write processes from a connected
  unit iostat can take different values
• positive value - an input error occured
• negative value - end of data is encountered, no
  input errors
• zero value - non of the above

41
iostat

• example
• real Temperature, Pressure, SumOfPressures0.0
• do
• read (12, fmt, iostat InputStatus) Code,
  Temperature, Pressure
• ! If end of data, terminate repetition
• if (InputStatus lt 0) exit
• ! If input error, stop execution
• if (InputStatus gt0) stop Input error
• ! Otherwise continue processing data
• Count Count 1
• SumOfPressures SumOfPressures Pressure
• end do

42
File processing

• to reposition a file at its beginning use a
  rewind statement
• rewind unit-number
• to reposition a file at the beginning of the
  preceding line use backspace statement
• backspace unit-number

43
Homework 4

• PART 1. Given the statements,
• real a
• character (LEN2) string
• logical ok
• read ( , '(F10.3, A2, L10) ) a, string, ok
• what would be read into a, string and ok if the
  following input
• records were used?
• (a) bbb5.34bbbNOb.true.
• (b) 5.34bbbbbbYbbFbbbbb
• (b) b6bbbbbb3211bbbbbbT
• (d) bbbbbbbbbbbbbbbbbbF
• where b represents a space or a blank character.

44
Homework 4

• PART 2.
• Write a Fortran program which will prompt the
• user for a file name, open that file and then
• read the file line by line outputting each line
  to
• the screen prefixed with a line number.

45
Homework 4

• send your homework to
• http//homework.itu.edu.tr