# Fortran/Mixing languages

## TypesEdit

Fortran types map quite well to intrinsic types in other compiled languages. The following is a table of Fortran-to-C types:

```
Fortran C
======= =
COMMON extern struct
INTEGER*1 signed char
INTEGER*2 short
INTEGER*4 long
INTEGER*8 long long
INTEGER int
REAL float
REAL*4 float
REAL*8 double
REAL*16 long double
LOGICAL int
LOGICAL*n char [n]
CHARACTER*n char [n]
DOUBLE PRECISION double
COMPLEX float [2]
COMPLEX*8 float [2]
COMPLEX*16 double [2]
COMPLEX*32 long double [2]
```

## ArraysEdit

In Fortran, the leftmost array subscript changes the fastest, not the slowest, so the item following x(1,1) is x(2,1), not x(1,2). By default the index of the first element of an array is 1, not 0.

## Global StorageEdit

See the Common Blocks section.

## Subroutine and Function CallsEdit

Many languages push their arguments onto the stack, some as constants and some as addresses. In most compilers, Fortran will compile a block of pointers to variables and constants, and push the address of that block. So, if we had a Fortran procedure defined as follows:

```
subroutine my_sub(i, j, x)
```

then the C definition would be:

```
struct my_sub_args {
int *i;
int *j;
float *x;
} my_sub_args = {&i, &j, &x};
void my_sub(my_sub_args*);
```

The C code could call the routine as follows:

```
my_sub(&my_sub_args);
```

## The PL/1 Special CaseEdit

In PL/1, you can define an external common block, subroutine, or procedure to be of type FORTRAN. When you do this, everything, down to subscript order, will be handled for you. Likewise, you can define a PL/1 item, such as a subroutine, to be of type FORTRAN, and it will then be callable by Fortran using Fortran's calling conventions.