Programming with FORTRAN (In a nut shell)
FORTRAN character set
Alphabets: a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z
Digits: 0 1 2 3 4 5 6 7 8 9
Symbols: + - * / . , ‘ _ ( )
FORTRAN constants
Two types: Character constant, Numeric constants
Numeric constants: Integer and Real
FORTRAN variables
Two types: Character variable, Numeric variables
Numeric variables: Integer and Real
Declaration: INTEGER list of variables
REAL list of variables
IMPLICIT type (…….)
Library functions
Common
functions
Trigonometric
functions
Inverse Trigonometric
functions
Hyperbolic
functions
sqrt(x)
exp(x)
log(x)
log10(x)
abs(x)
sin(x)
cos(x)
tan(x)
asin(x)
acos(x)
atan2(x,y)
sinh(x)
cosh(x)
tanh(x)
x: in radian
FORTRAN coding sheet
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Coding sheet is a paper with 80 columns
If the character C or ! is written in the first column, the line is treated as a comment line and it is not read by the
computer
Statements are written starting from 7th column and up to 72th column
If one statement is continued in the next line, then a character must put at the sixth column of the later line
Column 1-5 are used for giving line numbers in FORTRAN
Data files
opening a file:
open (no, file =’name’,status=’old’)
ending a file:
endfile m
m is the file number
Read Statement
read(n,m) v1,v2,…
n: input file number (* for reading from the screen)
m: input data format (* for free format)
v1,v2,… : input arguments
Write Statement
write(n,m) v1,v2,…
n: output file number (* for writing at the screen)
m: output data format (* for free format)
v1,v2,… : input arguments
Formatting of data
I format (For Integer data):
Iw (w is the width of the integer data)
F format (For real data):
Fw.d (w is the total width including sign, dot and decimal point; d is the number of decimal point)
E format (For real data):
Ew.d (w is the total width including sign, dot and decimal point; d is the number of decimal point)
X format (to skip some columns):
nX (n is the number of columns to be skipped)
/ format (to skip to the next line)
Control statements
GO TO statements
1. Unconditional go to statement:
go to n (n is the statement number)
2. Computed go to statement:
go to (n1,n2,…), i (n1,n2,… are the statement numbers and i is an integer)
If i =1, go to n1, if i =2, go to n2 …
IF statements
1. Arithmetic IF statement:
If (expression) n1, n2, n3
n1 is for negative, n2 is for zero and n3 is for positive
2. Conditional IF statement:
If (condition) statement
<
.LT.
>
.GT.
<= .LE.
>= .GE.
=
.EQ.
.NE.
Moreover .AND. , .OR. May be used
3. IF THEN ELSE statement:
Type1:
If (condition) then
s1
s2
.
.
. endif
Type2:
If (condition) then
s1
s2
.
.
.
else
s1’
s2’
.
.
.
endif
4 Nested IF THEN ELSE statement:
IF THEN ELSE statement within one or more IF THEN ELSE statement not crossing each other
DO loops
do I v=v1, v2, v3
……………..
……………..
I continue
i.e. I is the last statement in the DO loop
v is the running variables (integer/real); v1 is the initial value (integer/real); v2 is the final value (integer/real); v3 is the
increment (integer/real)
Rules:
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The statement number I must be a valid statement number which occurs after the DO statement i.e. the last
statement.
There must be one blank space each before and after the line number
v is an unsigned valid unsigned integer or real variables
v1,v2,v3 are valid variables, constants or expressions (integer or real)
If v3 is omitted, it is assumed to be 1
The value of the running variable should not be altered within the loop
Control cannot be transferred from a statement outside the DO loop to statement inside the DO loop
Control should not be transferred from a statement with in the DO loop to the do statement itself
Control cannot be transferred from a statement within the DO loop to statement outside the DO loop
The last statement of a DO loop should not be a control statement, i.e. the last statement should not be a go to
statement, if statement or another DO loop.
Nested do loops:
When one DO loop is constructed within another do loop, it is called a nested do loop.
Rules:
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DO loops should not overlap
In case of nested DO loop, the same statement can be the last statement for more than one DO loop
The running variable name of the outer loop should not be used as running variable for an inner nested DO loop
Array
If A is a sub scripted variable then:
dimension A (array length)
For multi dimensional sub scripted variables:
dimension A (array length1, array length 2, ...)