找到了：
main()
{unsigned getbits(unsigned,int,int);
unsigned int a;
int n1,n2;
printf("input an number");
scanf("%o",&a);
printf("input n1 and n2");
scanf("%d%d",&n1,&n2);
printf("output:%o\n",getbits(a,n1-1,n2));
}
unsigned getbits(unsigned value,int n1,int n2)
{unsigned z,z1,z2;
z=~0;
z1=z>>n1;
z2=z<<(16-n2);
z=z1&z2;
z=value&z;
z=z>>(16-n2);
return(z);
}

unsigned getbits(unsigned value,int n1,int n2)
{
return(value>>n1&~(~0<<n2-n1+1));
}

是这个意思吧.

/*楼主代码的简化(未经细致验证)*/
#include<stdio.h>
unsigned short getbits(unsigned short value,int n1,int n2)
{
return(value&0xffff>>n1)>>16-n2;
}
main()
{
unsigned short a;
int n1,n2;
printf("input an number ");
scanf("%o",&a);
printf("input n1 and n2 ");
scanf("%d%d",&n1,&n2);
printf("output:%o\n",getbits(a,n1-1,n2));
}

谢谢各位了