[THINKING IN C++]CHAPTER 03:EX 25

原创于 2008-05-17 23:31:00 发布 · 595 阅读

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#c++ #float #c

本文通过定义一个浮点变量并使用指针操作，展示了如何查看和修改浮点数在内存中的二进制表示形式。文章包括了C++代码示例，详细解释了如何将浮点数地址转换为字符指针，并利用此指针打印出浮点数的位模式。

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//25. Define a float variable. Take its address, cast that address
//to an unsigned char, and assign it to an unsigned char
//pointer. Using this pointer and [ ], index into the float
//variable and use the printBinary( )function defined in
//this chapter to print out a map of the float (go from 0 to
//sizeof(float). Change the value of the float and see if
//you can figure out what’s going on (the float contains
//encoded data).

//这题要看书p189的例子

#include<iostream>
using namespace std;

void main() {
    float fv;
    unsigned char *p = reinterpret_cast<unsigned char*>(&fv);

    void printBinary(const unsigned char);

    cout<<"fv= "<<fv<<endl;
    for(int j = 0; j < sizeof(float); j++){
        cout<<"p["<<j<<"]:";
        printBinary(p[j]);
        cout<<endl;
    }
}

//: C03:printBinary.cpp {O}
void printBinary(const unsigned char val) {
  for(int i = 7; i >= 0; i--)
    if(val & (1 << i))
      std::cout << "1";
    else
      std::cout << "0";
} ///:~