Chapter 1th C + + and STL Express

1.1 Basic knowledge of C + +

1.1.1 Small program "Hello World"

Annotations, preprocessing directives, main () functions, input/output streams

1. Note: Single-line comments use//Multiline comment/* ...

2. Preprocessing command: Start with a # character, such as: #include <iostream>, function: Extracts all the contents of the <iostream> header file and provides it to the current file. Header file function: Declaring functions defined elsewhere

Note: In C, files that are included usually end with. h, such as <stdio.h>. In C + +, the header file omits this suffix, such as <iostream>. But the standard header file in C still exists in C + +, just changing the name. As:<stdio.h> became a <cstdio>

Table 1-1: Common pre-processing commands

preprocessing commands	Function	Common usage
#include [file]	Inserts the specified file into the code where the instruction is located	is almost always used to include header files so that code can use features defined in other locations
#define [Key][value]	Each specified key is replaced with the specified value	In C, it is common to define numeric values or macros. C + + provides better constants and macro-definition mechanisms, and macros are risky to use, so use them sparingly in C + +
#ifdef [Key] #endif #ifndef [Key] #endif	The code in IFDEF ("if defined") Block or ifndef ("if not define") is conditionally included or discarded, depending on whether the specified key is defined with a # define	Often used to prevent loops from being contained. Each contained file begins with #ifndef to determine that a value is not defined, and then defines the value. The included file ends with #endif so that the header file is not included in multiple
#pragma [XYZ]	XYZ varies by compiler. If you perform this instruction during preprocessing, a warning or error message is typically displayed	Http://www.360doc.com/content/10/0902/09/2795334_50552950.shtml

3.main (): Program entry, return int value indicates the final execution state of the program, can have no parameters or have two parameters. such as int main (int argc, char* argv[]), where ARGC: arguments to the number of arguments to the program, argv: contains these parameters. Note: argv[0] may be the name of the program, but it should not be relied upon and should never be used.

4. Input/output stream: Std::cin std::cout

1.1.2 namespaces: Used to handle name collisions between different pieces of code. Use directives are used to avoid specifying a namespace, or you can use a using directive to reference a specified item using Std::cout within a namespace. Warning: You cannot use a using directive or a using declaration in a header file, or everyone will include your header file.

1.1.3 Variable

Chapter 1th C + + and STL Express