Fortran to C (Translation) by PK Mohanty, SINP, Kolkata-107

Statements

Fortran (77)

Remarks

Structure (1)

Col. 1    :  c or * for comments
Col. 2-5  : Statement label (optional)
Col. 6    : Continua of prev. line (optional)
Col. 7-72 : Statements
Col. 73-80: Sequence number

Structure Free
Statement ends with ;
Case sensitive

Variable types

integer, real,double, character 
 complex,logical

int,float, double, char 
(C does not have logical or complex var)
true and false are integer 1 and 0.

Var Declaration

integer a,b,c
real x,y

int a,b,c;
real x,y ;

Innitialization

real x,y
integer a,b
data x/1.2/, a/12/

float x=1.2,y
int a=12,b;

Oporators (mathematical)

+,-, *, /, **

+,-,*, /, %, ++,--
+=, -= ,*= ,/=

Oporators (logical)

.ge. , .gt. , .eq. , .or. , .and., .ne, .not.

>, >= , ==, ||, &&, !=, !

Control transfer

do 10 i, 1, 100, 2
DO-WHATEVER
10 end do

     while (i.lt. 100) do
         DO-WHATEVER  
      enddo

f(i.lt. 100) then
       DO-WHATEVER
      else 
       DO-otherwise
      enddo

goto 40

40 x= x+1

for(i=1;i<=100,i+=2)
{DO-WHATEVER ;}

while( i<100 )
{DO-WHATEVER ;}

if( i<100) {DO-WHATEVER ;}
else {DO-othrwise}

goto there
label there : x++

goto is usually not used in C.

The label there can be anything

Array

real a(5), b(5,10)
int c(2), k
data k/1/, c/19,45/

float a[5], b[5][5]
int c[]={19,45}, k

Array Index
F : 1 to N
C: 0 to N-1

Function

      real function add(m,t)
      integer m
      real t
      mult= t*m
      return
      end

float mult(int m, float t)
{ return(t*m);}

Subroutine

      subroutine iswap (a, b)
      integer a, b,t
      t = a
      a = b
      b = t
      return
      end

void iswap(a,b)
{int a,b,t; t=a;a=b;b=t}

Subroutine is a void function in C.

A complete program

c ----- Butterfly diagram-----
c ----------Logistic Map------
       	real x, a,f 
	integer i 
        do 10  a=0,4,.02
        x= .15 
        do 20 i=0,1000 
        x= f(x,a)
 20     enddo 
        do 30 i=0,100
        x= a*x*(1-x)
        write(*,*) a,x
 30     enddo
 10     enddo 
         stop
         end 

       real function   f(y,b)
        real y,b
        f= b* y*(1-y)
        return
        end

#include<stdio.h>
/*----- Butterfly diagram-----
----------Logistic Map------*/
main()
{
 float x,a,f(float,float);
 int i;

 for(a=0;a<4;a+=.02)
 {
   x=.15;
   for(i=0;i<1000;i++)x= f(x,a); 
   for(i=0;i<100;i++)
   {x= f(x,a); printf("%lf %lf\n",a, x);}
  }
}

float  f( float y, float b)
   {return( b* y*(1-y));}

Files

I will add more to it in few days. PK.