iostream

How do I print a double value with full precision using cout?

早过忘川 提交于 2019-11-25 22:16:54
问题 So I\'ve gotten the answer to my last question (I don\'t know why I didn\'t think of that). I was printing a double using cout that got rounded when I wasn\'t expecting it. How can I make cout print a double using full precision? 回答1: You can set the precision directly on std::cout and use the std::fixed format specifier. double d = 3.14159265358979; cout.precision(17); cout << "Pi: " << fixed << d << endl; You can #include <limits> to get the maximum precision of a float or double. #include

C++: “std::endl” vs “\n”

有些话、适合烂在心里 提交于 2019-11-25 21:41:31
问题 Many C++ books contain example code like this... std::cout << \"Test line\" << std::endl; ...so I\'ve always done that too. But I\'ve seen a lot of code from working developers like this instead: std::cout << \"Test line\\n\"; Is there a technical reason to prefer one over the other, or is it just a matter of coding style? 回答1: The varying line-ending characters don't matter, assuming the file is open in text mode, which is what you get unless you ask for binary. The compiled program will

How to print (using cout) a number in binary form?

孤街浪徒 提交于 2019-11-25 20:21:26
I'm following a college course about operating systems and we're learning how to convert from binary to hexadecimal, decimal to hexadecimal, etc. and today we just learned how signed/unsigned numbers are stored in memory using the two's complement (~number + 1). We have a couple of exercises to do on paper and I would like to be able to verify my answers before submitting my work to the teacher. I wrote a C++ program for the first few exercises but now I'm stuck as to how I could verify my answer with the following problem: char a, b; short c; a = -58; c = -315; b = a >> 3; and we need to show

C++ 基本的输入输出

允我心安 提交于 2019-11-25 19:31:02
一、C++ 基本的输入输出 C++ 标准库提供了一组丰富的输入/输出功能,我们将在后续的章节进行介绍。本章将讨论 C++ 编程中最基本和最常见的 I/O 操作。 C++ 的 I/O 发生在流中,流是字节序列。如果字节流是从设备(如键盘、磁盘驱动器、网络连接等)流向内存,这叫做输入操作。如果字节流是从内存流向设备(如显示屏、打印机、磁盘驱动器、网络连接等),这叫做输出操作。 1.1 I/O 库头文件 头文件 函数和描述 该文件定义了 cin、cout、cerr 和 clog 对象,分别对应于标准输入流、标准输出流、非缓冲标准错误流和缓冲标准错误流。 该文件通过所谓的参数化的流操纵器(比如 setw 和 setprecision),来声明对执行标准化 I/O 有用的服务。 该文件为用户控制的文件处理声明服务。我们将在文件和流的相关章节讨论它的细节。 1.2 标准输出流(cout) 预定义的对象 cout 是 iostream 类的一个实例。cout 对象"连接"到标准输出设备,通常是显示屏。cout 是与流插入运算符 << 结合使用的,如下所示: # include <iostream> using namespace std ; int main ( ) { char str [ ] = "Hello C++" ; cout << "Value of str is : " <<

How to print Unicode character in C++?

主宰稳场 提交于 2019-11-25 19:26:49
I am trying to print a Russian "ф" ( U+0444 CYRILLIC SMALL LETTER EF) character, which is given a code of decimal 1092 . Using C++, how can I print out this character? I would have thought something along the lines of the following would work, yet... int main (){ wchar_t f = '1060'; cout << f << endl; } To represent the character you can use Universal Character Names (UCNs). The character 'ф' has the Unicode value U+0444 and so in C++ you could write it '\u0444' or '\U00000444'. Also if the source code encoding supports this character then you can just write it literally in your source code. /