补码（负数）转换成原码

#include <stdio.h>

int main(void) { 
	
	unsigned char buma=0xc2;
	unsigned char fanma=0;
	signed char yuanma=0;
	unsigned char index,temp=0;
	
	printf("buma=%x\r\n",buma);
	
	fanma=buma-1;
	
	printf("fanma=%x\r\n",fanma);
	
	for(index=0;index<7;index++)
	{
	   temp=fanma>>index;
	   temp=~temp;
	   temp&=0x01;
	   temp=temp<<index;
	   yuanma+=temp;
	 }
	
	if(fanma&0x80)
	{
	   yuanma=-yuanma;
	}
	
	printf("yuanma=%d\r\n",yuanma);

	return 0;
}