printf的VS用C ++的cout [英] printf vs cout in C++

问题描述

是什么的printf（） 的区别C $ C> 和 COUT 在C ++？

What is the difference between printf() and cout in C++?

推荐答案

从 C ++ FAQ

[15.1]为什么我应该用＆LT; iostream的＆GT; 而不是传统的＆LT; cstdio＆GT; ？

[15.1] Why should I use <iostream> instead of the traditional <cstdio>?

增量式的安全性，减少错误，允许可扩展性，并提供可继承。

Increase type safety, reduce errors, allow extensibility, and provide inheritability.

的printf（）可以说是不破，而 scanf（）的尽管是容易出错也许宜居然而，无论是相对于什么C ++的I / O可以做限制。 C ++ I / O（使用＆LT;＆LT; 和＆GT;＆GT; ）是，相对于C（使用的printf（）和 scanf（）的）

printf() is arguably not broken, and scanf() is perhaps livable despite being error prone, however both are limited with respect to what C++ I/O can do. C++ I/O (using << and >>) is, relative to C (using printf() and scanf()):

  
• 更类型安全：使用＆LT;＆iostream的GT; ，对象被I / O类型为
    由编译器静态地已知的。在
    相反，＆LT; cstdio＆GT; 使用％领域
    动态地指出类型。

  
• 更少的错误倾向：使用＆LT;＆iostream的GT; ，没有多余的
    ％标记的必须是一致的
    与实际物体被I / O。
    去除多余的去除了一类
    的错误。

  
• 扩展：在C ++ ＆LT;＆iostream的GT; 机制允许新的用户定义
    类型被I / O不破
    现有code。试想一下，如果乱
    每个人都同时加入
    新的不相容的％领域
    的printf（）和 scanf（）的？！

  
• 可继承：C ++的＆LT;＆iostream的GT; 机制是从真正的类建
    如的std :: ostream的和
    的std :: istream的。不像＆LT; cstdio＆GT; 的
     FILE * ，这些都是真正的类和
    因此可继承。这意味着你可以
    有其它用户定义事
    外观和行为像流，然而这
    做什么奇妙的
    你想要的东西。您自动
    获得使用的无数行的
    有用户写的I / O code你不
    甚至不知道，并且它们不需要
    了解你的扩充流
    类。

  

• More type-safe: With <iostream>, the type of object being I/O'd is known statically by the compiler. In contrast, <cstdio> uses "%" fields to figure out the types dynamically.
• Less error prone: With <iostream>, there are no redundant "%" tokens that have to be consistent with the actual objects being I/O'd. Removing redundancy removes a class of errors.
• Extensible: The C++ <iostream> mechanism allows new user-defined types to be I/O'd without breaking existing code. Imagine the chaos if everyone was simultaneously adding new incompatible "%" fields to printf() and scanf()?!
• Inheritable: The C++ <iostream> mechanism is built from real classes such as std::ostream and std::istream. Unlike <cstdio>'s FILE*, these are real classes and hence inheritable. This means you can have other user-defined things that look and act like streams, yet that do whatever strange and wonderful things you want. You automatically get to use the zillions of lines of I/O code written by users you don't even know, and they don't need to know about your "extended stream" class.

在另一方面，的printf 是显著更快，这可以证明在preference用它来 COUT 中的非常的具体和有限的情况下。总是先轮廓。 （参见，例如，<一href=\"http://programming-designs.com/2009/02/c-speed-test-part-2-printf-vs-cout\">http://programming-designs.com/2009/02/c-speed-test-part-2-printf-vs-cout/)

On the other hand, printf is significantly faster, which may justify using it in preference to cout in very specific and limited cases. Always profile first. (See, for example, http://programming-designs.com/2009/02/c-speed-test-part-2-printf-vs-cout/)

这篇关于printf的VS用C ++的cout的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！