NCARG_CBIND(3NCARG)

💖 NCARG_CBIND — the C-binding era (3NCARG) 💖

okay so bestie, welcome to NCAR GRAPHICS, and welcome to the C-binding. this is the page that tells you how to use it. buckle up, it's giving ✨documentation✨ but make it cute.

---

🎀 NAME 🎀

NCAR Graphics C-binding — it's a description of how to use the NCAR Graphics C-binding. short, sweet, iconic. periodt.

---

🌸 SYNOPSIS 🌸

The NCAR Graphics C-binding is literally a whole collection of C routines that let you call NCAR Graphics Fortran routines from a C program without having to deal with the C-to-Fortran interface yourself. like, we handled that for you. you're welcome 🫶

For the detailed tea on the C-binding for any particular routine, go read the man page for the corresponding Fortran routine. that's where the real info lives.

A C-binding has been created for every user entry point in the NCAR Graphics utilities, with the exception of some of the obsolete utilities listed down below (yes, we'll get to them, don't worry). A GKS level 0A C-binding has also been created, and it adheres to the ISO/IEC standard. slay.

From here on out, when we say "a utility C-binding," we mean a C-binding for the NCAR Graphics utilities (AREAS, CONPACK, etc.). iykyk.

---

💅 NAMING CONVENTION 💅

For all of the utility user entry points, the name of the C-binding function is the same as the Fortran routine name with a c_ prepended. so for example, the C-binding for the CONPACK routine CPBACK is named c_cpback. cute, right?

but heads up — this naming convention does NOT apply to the GKS C-bindings. nope. not even a little.

For GKS, the C-binding names are more descriptive instead, like gset_fill_colr_ind, which is equivalent to the Fortran routine GSFACI. so please go see the man page for ncarg_gks_cbind(3NCARG) and the GKS Fortran routine to get the name of the corresponding GKS C-binding name.

The C programming language is case sensitive, so for convenience the utility C-binding names and their arguments are all in lower case. and in this man page, the Fortran routines and their arguments will be referred to in upper-case. keeping it consistent bestie 💖

---

🦋 ARGUMENT LISTS 🦋

The argument list of each utility C-binding corresponds with the argument list of the corresponding Fortran routine — except in some cases where multi-dimensioned arrays and/or character strings are involved. those exceptions get their own sections, and they're coming right up.

The C-binding argument list being similar to the Fortran argument list makes using the C-bindings way easier for people who already know the calling sequence of a particular Fortran routine. like, muscle memory but bilingual. For example, the NCAR Graphics routine PLCHHQ has this argument list:

PLCHHQ(REAL X, REAL Y, CHARACTER CHRS, REAL SZ, REAL ANG, REAL CNTR)

and the corresponding C-binding c_plchhq has the same type of argument list:

c_plchhq(float x, float y, char *chrs, float sz, float ang, float cntr)

see? same vibe, different language. iconic. ✨

---

🌈 ARRAYS 🌈

okay so one of the exceptions to the utility C-binding argument lists has to do with multi-dimensioned arrays. here's the thing: in Fortran, arrays are stored in column-major order, while in C they are stored in row-major order. this means the subscripts of a multi-dimensioned array need to be switched before passing the array to a Fortran routine from C. no cap.

As an example, the CONPACK routine CPRECT takes a two-dimensional array, ZDAT, as one of its arguments. If the Fortran dimensions of ZDAT are to be 25 x 14, then in the C program you must dimension ZDAT to be 14 x 25 before calling the C-binding c_cprect.

The next three arguments of CPRECT describe the array in question:

• The first of these three arguments, KZDT, is the first dimension of the array ZDAT as it is declared in the Fortran calling program. For CPRECT this value would be 25. For the C-binding c_cprect, however, this argument is the second dimension of the array as declared in the C program. This value would be 25 as well, since the subscripts had to be switched in the C program.
• The second and third of these three arguments (MZDT and NZDT) specify the number of elements in each row and column (respectively) to be contoured. If you only want to contour 20 x 10 of the array ZDAT, then MZDT and NZDT should be 20 and 10 respectively in CPRECT. For c_cprect, these variables specify the columns and rows, so again, the values would be 20 and 10 (because the subscripts have to be switched).

yes it's a lot. no you're not gonna remember it. yes you'll be fine. 💜

---

🎀 CHARACTER STRINGS 🎀

Another exception to the argument lists for the utility C-bindings has to do with routines that return character strings. The NCAR Graphics routines that return strings through the parameter list do not have a string length as part of their argument lists, so you must pass an extra argument to the C-binding which specifies the maximum length of the string.

Also, all input strings passed to the C-bindings must be null-terminated! do not forget this. it will ruin your day. 😭

For example, in the routine PCGETC, you pass a parameter name and it returns the value of that parameter, which in this case is a string. The two arguments to PCGETC are WHCH and CVAL, where WHCH is the parameter name and CVAL is the string to be returned. Since the C-binding c_pcgetc needs to know the length of cval, an extra argument of type "int" must be passed. Thus, the arguments for c_pcgetc would be whch, cval, and len, where len is the length of cval as it is declared in the C program.

In any case of having to add an extra argument for the string length, the extra argument will always be the last one in the list. If more than one string length argument needs to be added, then each one should be added at the end of the argument list in the order that their corresponding strings appear. order matters, bestie. it's giving choreography. 💅

There are some routines like AGDSHN which are defined as character strings themselves. In this case, the user does not need to pass a string length since it is already defined. But — plot twist — the string that is returned is declared statically, thus it will go away once you call the routine again. If you need to save these character strings, be sure to copy them to your own local variable. protect your data. 🫶

---

⭐ FUNCTION PROTOTYPES ⭐

The C-bindings are intended to be ANSI C compliant. To get the correct function prototypes for the utility C-bindings, you can include <ncarg/ncargC.h>. For the GKS C-bindings, include <ncarg/gks.h>.

In some cases, it may be necessary to typecast the arguments in the utility C-bindings to get the prototypes correct. For example, the C-bindings do not distinguish between singly and multiply dimensioned arrays, so if you are passing a multiply dimensioned float array, you may need to typecast it as a (float *) if this is not how it is declared in the main program.

---

🔥 COMPILING YOUR PROGRAM 🔥

To compile your NCAR Graphics C program with the C-bindings, use the NCARG application ncargcc. ncargcc will take care of loading in the necessary C/Fortran interface libraries as well as the NCAR Graphics C and Fortran libraries. she does it all, no stress. 👑

You will either need to set the NCARG_ROOT environment variable, or the NCARG_BIN, NCARG_LIB, and NCARG_INCLUDE environment variables, in order to run ncargcc. See man ncargintro for more information.

If you do not wish to use ncargcc, then you can just run it with no arguments to see what the necessary libraries are, and then put this information in your Makefile or whatever else you are using to compile and link your program.

Note: if you have an ANSI C compiler, it is important that you define the macro NeedFuncProto on the compile line so that function prototyping is included. do not skip this. 🙈

---

🧚 EXAMPLES 🧚

A few examples of C programs that call the NCAR Graphics C-bindings have been provided for your convenience. You may be familiar with the output from these C programs, as they were modeled after the Fortran programs that you can get with the ncargex command. cute crossover moment.

To copy any one of these C programs into your directory, and then compile, link, and run it, type:

ncargex xxxx

where xxxx is the name of the example you wish to generate. To see a list of all the C examples, type:

ncargex -C -list

ncargex uses ncargcc to compile and link the C-binding example programs. teamwork makes the dream work. ✨

---

💀 OBSOLETE ROUTINES 💀

C-bindings have not been provided for user entry points in the following obsolete utilities:

• Conran_family
• Conrec_family
• Halftone
• Isosrfhr
• Pwrite_family

that's the whole list. they're retired, we don't talk about them. 🫶

---

🌟 SEE ALSO 🌟

Online:

• ncargcc(1NCARG)
• ncargex(1NCARG)
• ncarg_gks_cbind(3NCARG)
• ncargintro(5NCARG)

Hardcopy:

• NCAR Graphics Fundamentals, UNIX Version
• User's Guide for NCAR GKS-0A Graphics

---

👑 COPYRIGHT 👑

Copyright (C) 1987-2002 University Corporation for Atmospheric Research

The use of this Software is governed by a License Agreement.

---

and that's the whole page bestie, you ate it 💅 this was NCAR GRAPHICS, the February 1993 edition, filed under NCARG_CBIND(3NCARG). go compile something iconic. 🦋✨