C语言使用全局常量
示例
标头可用于声明全局使用的只读资源，例如字符串表。
在单独的标头中声明这些标头，该标头将包含在任何要使用它们的文件中（“翻译单元”）。使用相同的标头声明一个相关的枚举来标识所有字符串资源很方便：
resources.h：
#ifndef RESOURCES_H
#define RESOURCES_H
typedef enum { /* Define a type describing the possible valid resource IDs. */
RESOURCE_UNDEFINED = -1, /* To be used to initialise any EnumResourceID typed variable to be
marked as "not in use", "not in list", "undefined", wtf.
Will say un-initialised on application level, not on language level. Initialised uninitialised, so to say ;-)
Its like NULL for pointers ;-)*/
RESOURCE_UNKNOWN = 0, /* To be used if the application uses some resource ID,
for which we do not have a table entry defined, a fall back in
case we _need_ to display something, but do not find anything
appropriate. */
/* The following identify the resources we have defined: */
RESOURCE_OK,
RESOURCE_CANCEL,
RESOURCE_ABORT,
/* Insert more here. */
RESOURCE_MAX /* The maximum number of resources defined. */
} EnumResourceID;
extern const char * const resources[RESOURCE_MAX]; /* Declare, promise to anybody who includes
this, that at linkage-time this symbol will be around.
The 1st const guarantees the strings will not change,
the 2nd const guarantees the string-table entries
will never suddenly point somewhere else as set during
initialisation. */
#endif为了实际定义资源，创建了一个相关的.c文件，这是另一个翻译单元，其中包含相关标头(.h)文件中声明的内容的实际实例：
resources.c：
#include "resources.h" /* To make sure clashes between declaration and definition are
recognised by the compiler include the declaring header into
the implementing, defining translation unit (.c file).
/* Define the resources. Keep the promise made in resources.h. */
const char * const resources[RESOURCE_MAX] = {
"<unknown>",
"OK",
"Cancel",
"Abort"
};使用此程序的程序可能如下所示：
main.c：
#include <stdlib.h> /* for EXIT_SUCCESS */
#include <stdio.h>
#include "resources.h"
int main(void)
{
EnumResourceID resource_id = RESOURCE_UNDEFINED;
while ((++resource_id) < RESOURCE_MAX)
{
printf("resource ID: %d, resource: '%s'\n", resource_id, resources[resource_id]);
}
return EXIT_SUCCESS;
}使用GCC编译上面的三个文件，并将其链接为程序文件main，例如，使用以下命令：
gcc -Wall -Wextra -pedantic -Wconversion -g main.cresources.c -o main
（使用它们-Wall-Wextra-pedantic-Wconversion可以使编译器真正变得挑剔，因此在将代码发布到SO之前，您不会错过任何东西，可以说是个不错的选择，甚至值得将其部署到生产环境中）
运行创建的程序：
$ ./main
得到：
resource ID: 0, resource: '<unknown>' resource ID: 1, resource: 'OK' resource ID: 2, resource: 'Cancel' resource ID: 3, resource: 'Abort'