#include <iostream>
using namespace std;
   
int main()
{
    const float KG_PER_POUND=0.454;
    float pounds,
        kgs;
    cout<<"Enter the weight in pounds:";
    cin>>pounds;
    float   kgs=KG_PER_POUND*poundS;
    cout<<"The weight in kilograms is"<<kgs<<endl;
    renturn 0;
}   

  kgs = KG_PER_POUND * pounds; //这里重复定义kgs, pounds打错了
这句删掉吗？我删了还不行。你能给我说应怎么改好吗？谢谢了

编译器说有错误，要把程序改成cpp格式，怎么改呀？

弄好了，谢谢你，请问const float KG_PER_POUND=0.454f;为什么加f?