Lesson 5 - Learning Goals



5.1 Introduction to Read


5.2 Character Formats

5.3 Logical Formats

5.4 How to deal with Formatting Problems

5.5 Mixing Strings

5.6 What is Carriage Control

5.7 How to debug a program


PROGRAM P22

!

! INTRODUCTION TO READ

!

IMPLICIT NONE

INTEGER :: I,J,AGE,POUNDS,GRAMS

REAL :: DAYS

CHARACTER (LEN=15) :: NAME,ADDRESS

LOGICAL :: SINGLE

!

PRINT *, 'This is Program >> P22 - Read in some data'

!

! READ DATA

!

READ *,I

!

DO J=1,I

READ * ,AGE,POUNDS

READ * ,NAME,ADDRESS

READ * ,SINGLE

!

! EXECUTABLE STATEMENTS

!

GRAMS=POUNDS*254

DAYS=AGE*365.25

!

! PRINT DATA

!

PRINT *,'NAME AND ADDRESS :'

PRINT *, NAME,ADDRESS

PRINT *,'AGE AND NUMBER OF DAYS :'

PRINT *, AGE,DAYS

PRINT *,'POUNDS AND GRAMS :'

PRINT *, POUNDS,GRAMS

PRINT *,'SINGLE :'

PRINT *, SINGLE

PRINT *,' '

!

END DO

STOP

END PROGRAM P22


1.LOGICAL COMPARISONS

!

PROGRAM COMPARISON

!

IMPLICIT NONE

LOGICAL :: COMPAR

INTEGER :: I

PRINT *,2+2 = = 4, 5<=3, 1>=1

PRINT *,-1.4>-1.9, I /= 3, I = = 3.0

PRINT *, 'A' < 'B', 'JOHN ROE' < 'JOHN DOE'

COMPAR='LONG' >= 'LONGEST'

PRINT *,COMPAR

STOP

END PROGRAM COMPARISON

PROGRAM OUTPUT :

T F T

T F T

T F

F


2. FORMAT STATEMENT

The General form is :

          label FORMAT ( layout information )

where

label

          is a statement number from 1 to 99999

FORMAT

Keyword defining this non­executable statement which can be placed anywhere in the program

layout information

is any combination of a number of conversion types or edit descriptors which specify the kind of variable and constant data and its location on the input record (card) or output record (line).

The most used conversion types can be summarized as follows.

General Conversion

Form
Example
Type
nIw
3I10
INTEGER
nFw.d
4F20.5
REAL Fixed point form
nEw.d
4E20.7
REAL Exponent form
nGw.d
2G15.0
REAL or INTEGER (General form)
nLw
2L5
LOGICAL
nAw
2A20
CHARACTER
nX
15X
Skip a number of columns
Tn
T30
TAB to a given column
`...'
`TITLE'
Output CHARACTER constant
r(...)
3(2X,A4)
Repeat section in brackets


READING WITH FORMAT STATEMENTS

...

          READ 44,INTl,INT2,INT3

          44 FORMAT (3I5)

          PRINT 44,INTl,INT2,INT3

          STOP

          END PROGRAM READING

/DATA

432 ­333 1

OUTPUT :

432 ­333 1

...

      READ 44,INTl,INT2,INT3

44    FORMAT (3(' ',I3))

      PRINT 44,INTl,INT2,INT3

      STOP

      END PROGRAM READING2

/DATA

432 ­333 1

OUTPUT :

432 ­33 10


MISCELLANEOUS FORMATTING

1. Repeats

PRINT 15,2,'ABC',4.4,'DEF',­2.13

15 FORMAT (' ',I3,2(' ',A3,'=',F7.2))

2 ABC= 4.40 DEF= ­2.13

2. Multiple lines

PRINT 20,444,­2.131

20 FORMAT (' ',I3/' ',F7.2)

444

­2.13

3. Wrong number of arguments

PRINT 30,'SEP'

PRINT 30

PRINT 30,'OCT',31,'NOV',30

30 FORMAT (' ',A3, '=', I2)

SEP=

OCT=31

NOV=30


MIXING STRINGS

Operation
Size of
Result
x
y
x = y
10
20
Left half of y => x
x = y
20
10
y + 10 spaces => x
x = 'HELLO'
10
HELLO' + 5 spaces => x
PRINT *,x
10
10 chars printed
x == y (>, etc)
20
10
x compared to y + spaces
READ 10,X
10
x only gets left
10 FORMAT (Ay)
20
half of input string
READ 10,X
20
x gets 10 characters
10 FORMAT (Ay)
10
of input data + 10 spaces
READ 10,X
10
10 spaces + x
10 FORMAT (' ',Ay)
20
printed
READ 10,X
20
Leftmost 10 characters
10 FORMAT (' ',Ay)
10
of x printed



CARRIAGE CONTROL

Control Characters
Character
Coded As
Vertical spacing
one
' 1 '
New page
blank
' '
Single spacing
zero
' 0 '
Double spacing
plus
' + '
No spacing



DEBUGGING A PROGRAM

1) READ COMPLETE PROGRAM SLOWLY FROM TOP TO BOTTOM

          - Properly structured

          - Proper header

          - Proper syntax

          - Variables appropriately declared

          - Blocks indented

2) COMPILE PROGRAM

          - Any errors

          - Any warnings

          - Refer to ISN (Internal Statement Numbers)

          - Clean compile

          - Missing routines at link

3) EXECUTION TIME ERRORS

          - No output, add print statement

          - ''Stuck in a loop'' = too much output !


DYNAMIC - INTERACTIVE DEBUGGING

1) GENERAL CONCEPT

- Your program is available in source form (e.g. FORTRAN, C, PASCAL, etc. ) and in BINARY.

- Your program is run under the control of debugger.

- Debugger allows :

          - Inspection of data input/output

          - Single step execution

          - Breakpoints

          - Tracing

          - Animation

          - Full speed execution

          - Array subscript checking

2) FORTRAN :

          ELF90 - Essential LAHEY FORTRAN 90

3) C language :

          A) Turbo C

          B) Turbo Pascal version 6


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