HP 3000 Manuals HP 3000 Manuals
Comparing HP C and HP FORTRAN 77
Table 3-2 shows the differences in storage allocation between HP C
and HP FORTRAN 77. The notes the table refers to are located after the
table in the section called "Notes on HP C and HP FORTRAN 77."
Table 3-2. HP C versus HP FORTRAN 77 Storage
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| | | | |
| HP C Type | HP C Description | HP FORTRAN 77 Type | HP FORTRAN 77 |
| | | | Description |
| | | | |
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| | | | |
| char, signed char, | 1 byte, | -- | 1 byte, |
| char enum | byte aligned | | 1-byte aligned |
| | | | |
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| | | | |
| unsigned char | 1 byte, | CHARACTER*1 | 1 byte, |
| | byte aligned | | 1-byte aligned |
| | | | |
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| | | | |
| short, short enum | 2 bytes, | INTEGER*2 | 2 bytes, |
| | 2-byte aligned | | 2-byte aligned |
| | | | |
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| | | | |
| unsigned short | 2 bytes, | -- | -- |
| | 2-byte aligned | | |
| | | | |
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| | | | |
| int, int enum | 4 bytes, | INTEGER*4 or INTEGER | 4 bytes, |
| | 4-byte aligned | | 4-byte aligned |
| | | | |
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| | | | |
| unsigned int | 4 bytes, | -- | -- |
| | 4-byte aligned | | |
| | | | |
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| | | | |
| long, long enum | 4 bytes, | INTEGER*4 or INTEGER | 4 bytes, |
| | 4-byte aligned | | 4-byte aligned |
| | | | |
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| | | | |
| unsigned long | 4 bytes, | -- | -- |
| | 4-byte aligned | | |
| | | | |
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| | | | |
| float | 4 bytes, | REAL or REAL*4 | 4 bytes, |
| | 4-byte aligned | | 4-byte aligned |
| | | | |
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| | | | |
| double | 8 bytes, | REAL*8 or DOUBLE | 8 bytes, |
| | 8-byte aligned | PRECISION | 8-byte aligned |
| | | | |
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| | | | |
| long double | 16 bytes, | REAL*16 | 16 bytes, |
| | 16-byte aligned | | 16-byte aligned |
| | | | |
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| | | | |
| (See Note 1) | 8 bytes, | COMPLEX or COMPLEX*8 | 8 bytes, |
| | 4-byte aligned | | 4-byte aligned |
| | | | |
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| | | | |
| (See Note 2) | 16 bytes, | DOUBLE COMPLEX or | 16 bytes, |
| | 8-byte aligned | COMPLEX*16 | 8-byte aligned |
| | | | |
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Table 3-2. HP C versus HP FORTRAN 77 Storage (cont.)
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| | | | |
| HP C Type | HP C Description | HP FORTRAN 77 Type | HP FORTRAN 77 |
| | | | Description |
| | | | |
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| | | | |
| enum | 4 bytes, | INTEGER*4 or INTEGER | 4 bytes, |
| | 4-byte aligned | | 4-byte aligned |
| | | | |
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| | | | |
| pointer to type long | -- | Not available | -- |
| pointer to type | | | |
| | | | |
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| | | | |
| string (char *) | -- | CHARACTER*n (See Note | -- |
| | | 3) | |
| | | | |
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| | | | |
| char array | -- | CHARACTER*1 array | -- |
| | | (See Notes 4 & 5) | |
| | | | |
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| | | | |
| (See Note 5) | -- | Hollerith array | -- |
| | | | |
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| | | | |
| arrays | Size is number of | (See Note 4) | Size is number of |
| | elements times | | elements times |
| | element size. | | element size. |
| | Aligned according | | Aligned according |
| | to element type. | | to element type. |
| | | | |
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| | | | |
| struct | (See Note 6) | STRUCTURE | Used to declare |
| | | | FORTRAN 77 |
| | | | record structures. |
| | | | |
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| | | | |
| union | (See Note 6) | UNION | Used to declare |
| | | | FORTRAN 77 |
| | | | union types. |
| | | | |
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| | | | |
| short (Used for | 2 bytes, | LOGICAL*2 (See Note | 2 bytes, |
| logical test) | 2-byte aligned | 7) | 2-byte aligned |
| | | | |
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| | | | |
| int (Used for logical | 4 bytes, | LOGICAL*4 (See Note | 4 bytes, |
| test) | 4-byte aligned | 7) | 4-byte aligned |
| | | | |
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| | | | |
| void | -- | Used when calling a | -- |
| | - | SUBROUTINE | |
| | | | |
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| | | | |
| function | -- | Used when calling a | -- |
| | | FUNCTION | |
| | | | |
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Notes on HP C and HP FORTRAN 77
1. The following HP C structure is equivalent to the HP FORTRAN 77
type listed in the table:
struct complex {
float real_part;
float imag_part;
};
2. The following HP C structure is equivalent to the HP FORTRAN 77
type listed in the table:
struct double_complex {
double real_part;
double imag_part;
};
3. HP FORTRAN 77 passes strings as parameters using string
descriptors corresponding to the following HP C declarations:
char *char_string; /* points to string */
int len; /* length of string */
4. HP C stores arrays in row-major order, whereas HP FORTRAN 77
stores arrays in column-major order. The lower bound for HP C is
always zero; for HP FORTRAN 77, the default lower bound is 1.
5. HP C terminates character strings with a null byte, while HP
FORTRAN 77 does not.
6. The size is equal to the size of all members plus any padding
needed for the alignment. (See Chapter 2 for details on
alignment.) The alignment is that of the member with the
strictest alignment requirement.
7. HP C and HP FORTRAN 77 do not share a common definition of true or
false. In HP FORTRAN 77, logical values are determined by the
low-order bit of the high-order byte. If this bit is 1, the
logical value is .TRUE., and if the bit is zero, the logical value
is .FALSE.. HP C interprets nonzero value as true and interprets
zero as false.
Mixing C and FORTRAN File I/O
A FORTRAN unit cannot be passed to a C routine to perform I/O on the
associated file. Nor can a C file pointer be used by a FORTRAN routine.
However, a file created by a program written in either language can be
used by a program of the other language if the file is declared and
opened within the latter program. C accesses the file using I/O
subroutines and intrinsics. This method of file access can also be used
from FORTRAN instead of FORTRAN I/O.
Be aware that HP FORTRAN 77 on HP 9000 Series 700/800 computers using
HP-UX uses the unbuffered I/O system calls read and write (described in
the HP-UX Reference manual) for all terminal I/O, magnetic tape I/O, and
direct access I/O. It uses the system calls fread and fwrite for all
other I/O. This can cause problems in programs that mix C and FORTRAN
I/O. In particular, C programs that use stdio(3S) output procedures such
as printf and fwrite and FORTRAN output statements must flush stdio
buffers (by calling the libc function fflush) if they are in use before
returning to FORTRAN output or the I/O may be asynchronous (if the
library is using write).
Mixing FORTRAN direct, terminal, or tape READ statements with stdio fread
input results in the FORTRAN READ commencing from the beginning of the
next block after the contents of the buffer, not from the current
position of the input cursor in the fread buffer. The same situation in
reverse may occur by mixing read with a FORTRAN sequential disc read.
You can avoid these problems by using only the read and write calls in
the C program that the FORTRAN I/O library uses.
Passing Parameters Between HP C and HP FORTRAN 77
All parameters in HP FORTRAN 77 are passed by reference. This means that
all arguments in an HP C call to an HP FORTRAN 77 routine must be
pointers. In addition, all parameters in an HP C routine called from HP
FORTRAN 77 must be pointers, unless the HP FORTRAN 77 code uses the
$ALIAS directive to define the parameters as value parameters. Refer to
the example called "HP FORTRAN 77 Nested Structure" later in this
chapter.
Passing string variables of any length must be done by: building and
passing a two-parameter descriptor (defined in Note 3 above),
initializing the string appropriately, and by passing two arguments. The
two arguments are the pointer to the characters and the value of the
length word. This is shown below:
char *chars = "Big Mitt";
int len;
:
len = strlen(chars);
pass_c_string (chars, len);
:
Linking HP FORTRAN 77 Routines on HP-UX
When calling HP FORTRAN 77 routines on an HP-UX system, you have to
include the HP FORTRAN 77 run-time libraries by adding the option:
-lcl
to the cc command line.
For details on linking external libraries, see the -l option of the cc(1)
and ld(1) commands in the HP-UX Reference manual.
Linking HP FORTRAN 77 Routines on MPE/iX
The object file or files containing the HP FORTRAN 77 routines you want
to call must be added to the FROM list when linking. The HP FORTRAN 77
run-time libraries reside in the same file, XL.PUB.SYS, as the HP C
library so no additional action is necessary. For example:
LINK FROM=MYMAINO,MYCO,MYFORTO; TO=PROG; RL=LIBCINIT.LIB.SYS, &
LIBCANSI.LIB.SYS
links the HP C object files MYMAINO and MYCO with the HP FORTRAN 77
object file MYFORTO.