DOS SVGACC图形开发库函数

原型:extern int far whichxms (unsigned int far *xmskbytesavail, unsigned int far *xmshandlesavail)

输入:　无输入参数

输出:　如果探测到扩展内存则返回1，否则返回0

xmskbytesavail - 扩展内存的空闲大小(千字节数)

xmshandlesavail - 扩展内存的可用大小(千字节数)

用法:　WHICHXMS检测是否存在扩展内存支持，并且安装相应的库函数调用。这个函数必须在所有其它扩展内存函数调用之前调用。WHICHXMS同时还返回扩展内存的空闲大小和可用大小。可用大小是有限制的，一般为32。这个限制可以在CONFIG.SYS文件中修改扩展内存驱动(常用的是与微软兼容的HIMEM.SYS)命令行来改变。

例子

/*

* show what xms memory is available

*/

#include <stdlib.h>

#include <conio.h>

#include "svgacc.h"

void main(void)

{

int er, mem, handles;

if ( whichxms(&mem,&handles) ) {

printf("an active xms memory manager was found!\");

printf("a total of %d kb of xms memory

available...\",mem);

printf("a total of %d xms memory handles

available...\",handles);

printf(" \");

if ((mem < 1) || (handles < 1)) {

printf("sorry...there is either no free xms or\");

printf("no free handles\");

printf(" \");

printf("xms support not available...\");

exit(1);

}

else {

printf(" \");

printf("xms support is ready and available!\");

exit(1);

}

}

else {

printf("sorry...no active xms memory manager

found...\");

printf("make sure you have an xms memory manager\");

printf("(such as HIMEM.SYS) loaded\");

printf(" \");

printf("xms support not available...\");

exit(1);

}

exit(0);

}