1. Getting to know C++

1.1 first C + + program

To create a new project, select Create an empty project for C + +:

Select project name and location:

To add a C + + file to the source file:

# include <iostream>
using namespace std;

int main()
{
	// nowrap 
	cout << "hello world" ;
	// Line feed, line feed with < < endl
	cout << "hello world" << endl;
	// So this is a simple line feed
	cout << endl;

	system("pause");

	return 0;
}

1.2 notes

# include <iostream>
using namespace std;

// 1. Single line notes

/*
multiline comment 
*/

int main()
{

	cout << "hello world" << endl;

	system("pause");

	return 0;
}

1.3 variables and constants

Is to name a designated space to facilitate the operation of this space.
Create variable: data type variable name = variable initial value;

Constant: records data that cannot be changed in a program
How to define constants:

• #define macro constant: # constant name constant value
  • It is usually defined above the file to represent a constant.
• Const modified variable: const data type constant name = constant value
  • The keyword const is usually added before the variable definition to modify the variable as a constant and cannot be modified.

# include <iostream>
using namespace std;

# define Weekday 7

int main()
{

	const int a = 10;

	cout << "a = " << a <<endl;

	cout << "A week:" << Weekday << "day" << endl;


	system("pause");

	return 0;
}

1.4 keywords

Reserved words in C + + cannot be used when defining variables or constants

1.5 identifier naming rules

• Identifier cannot be a keyword
• The identifier can only be composed of letters, numbers and underscores
• The first character must be a letter or an underscore
• Letters in identifiers are case sensitive
• It is better to know its meaning through the identifier

2. Data type

The meaning of data type: allocate an appropriate memory space for variables.

Scientific counting method:

• 3e2: 3 * 102
• 3e-2:3 * 0.12

2.1 shaping

data type	Occupied space	Value range
Short (short integer)	2 bytes	(-215 ~ 215-1 )
int (integer)	4 bytes	(-231 ~ 231-1 )
Long (long shaping)	4 bytes for Windows, 4 bytes (32 bits) for Linux, 8 bytes (64 bits)	(-231 ~ 231-1 )
long long	8 bytes	(-263 ~ 263-1 )

2.2sizeof keyword

Memory occupied by statistics type

2.3 real (floating point)

data type	Occupied space	Significant digit range
float (single precision)	4 bytes	7 significant digits
Double (double)	8 bytes	15 ~ 16 significant digits

2.4 character type

Used to represent a single letter

• Character variables occupy only one byte.
• Character type variables do not store the character itself in memory, but put the corresponding ASCII code in the storage unit.

# include <iostream>
using namespace std;

int main()
{
	char ch = 'a';

	cout << ch << endl;
	cout << sizeof(ch) << endl;
	/*
	a
	1
	*/
	// ASCII encoding corresponding to character type variable
	// a 97
	// A 65
	cout << (int)ch << endl;
	// 97
	// You can assign values to character variables through ASCII
	char ch2 = 98;
	cout << ch2 << endl;
	// b

	system("pause");

	return 0;
}

Common errors:

• Use double quotation marks: char ch = "a";
• Put multiple characters in single quotation marks: char ch = 'asd';

ASCII code table

• ASCII non printing control characters: the numbers 0 ~ 31 on the ASCII table are assigned to the control characters, which are used to control peripheral devices.
• ASCII printed characters: the numbers 32 to 126 are assigned to characters that can be found on the keyboard and appear when viewing or printing a document.

ASCII value	Control character	ASCII value	character	ASCII value	character	ASCII value	character
0	NUT	32	(space)	64	@	96	`
1	SOH	33	!	65	A	97	a
2	STX	34	"	66	B	98	b
3	ETX	35	#	67	C	99	c
4	EOT	36	$	68	D	100	d
5	ENQ	37	%	69	E	101	e
6	ACK	38	&	70	F	102	f
7	BEL	39	，	71	G	103	g
8	BS	40	(	72	H	104	h
9	HT	41	)	73	I	105	i
10	LF	42	*	74	J	106	j
11	VT	43	+	75	K	107	k
12	FF	44	,	76	L	108	l
13	CR	45	-	77	M	109	m
14	SO	46	.	78	N	110	n
15	SI	47	/	79	O	111	o
16	DLE	48	0	80	P	112	p
17	DC1	49	1	81	Q	113	q
18	DC2	50	2	82	R	114	r
19	DC3	51	3	83	S	115	s
20	DC4	52	4	84	T	116	t
21	NAK	53	5	85	U	117	u
22	SYN	54	6	86	V	118	v
23	TB	55	7	87	W	119	w
24	CAN	56	8	88	X	120	x
25	EM	57	9	89	Y	121	y
26	SUB	58	:	90	Z	122	z
27	ESC	59	；	91	[	123	{
28	FS	60	<	92	\	124	|
29	GS	61	=	93	]	125	}
30	RS	62	>	94	^	126	~
31	US	63	?	95	-	127	DEL

2.5 escape characters

Function: used to display some ASCII characters that cannot be expressed directly.

Escape character	meaning	ASCII value (decimal)
\a	alert	007
\b	Backspace (BS) moves the current position to the previous column	008
\f	Page feed (FF) moves the current position to the beginning of the next page	012
\n	Line feed (LF) moves the current position to the beginning of the next line	010
\r	Enter (CR) moves the current position to the beginning of the line	013
\t	Horizontal tabulation (HT) (skip to next TAB position)	009
\v	Vertical tabulation (VT)	011
\\	Represents a backslash character '\'	092
\'	Represents a single quote character	039
\"	Represents a double quote character	034
\?	Represents a question mark	063
\0	Number 0	000
\ddd	Octal escape character, d range 0 ~ 7	3-bit octal
\xhh	Hexadecimal escape character, h range 09, af, A~F	3-bit octal

2.6 string type

Represents a string of characters

• Array style string: char variable name [] = "string value";
• C + + style string: string variable name = "string value"; (a header file is required: # include < string >)

2.7 boolean type bool

Represents true or false values
There are only two values:

• True: stands for true
• False: false

They are essentially 0 or 1, and the bool type takes up one byte.

2.8 data input

Get data from keyboard
Key words: cin

# include <iostream>
using namespace std;

int main()
{
	// 1. Shaping
	int a = 0;
	cout << "Please give integer variable a assignment:" << endl;
	cin >> a;
	cout << "Integer variable a = " << a << endl;

	// 2. Floating point type
	float f = 3.14f;
	cout << "Please give floating point variables f assignment:" << endl;
	cin >> f;
	cout << "Integer variable f = " << f << endl;
	
	// 3. Character type
	char ch = 'a';
	cout << "Please give a character variable ch assignment:" << endl;
	cin >> ch;
	cout << "Integer variable ch = " << ch << endl;
	
	system("pause");

	return 0;
}

3. Operator

Operator type	effect
Arithmetic operator	Used to process four operations
Assignment Operators	Used to assign the value of an expression to a variable
Comparison operator	Comparison for expressions
Logical operator	Used to return true or false values based on the value of an expression

3.1 arithmetic operators

operator	term	explain
+	Plus sign	Symbol
-	minus sign	Symbol
+	plus
-	reduce
*	ride
/	except
%	Mold taking (residual)	Remainder (two decimals cannot be modulo)
++	Pre increment	Add one first and then the operation of the expression
++	Post increment	First the operation of the expression, and then add one
–	Pre decrement	ditto
–	Post decrement	ditto

3.2 assignment operator

operator	term
=	assignment
+=	Plus equals
-=	Minus equals
*=	Multiply equal
/=	Division equals
%=	Modulo equal

3.3 comparison operators

operator	term
==	Wait for
!=	Not equal to
>	greater than
<	less than
>=	Greater than or equal to
<=	Less than or equal to

3.4 logical operators

operator	term
!	wrong
||	or
&&	And

4. Procedure flow structure

4.1 selection of structure

4.1.1 if statement

# include <iostream>
using namespace std;

int main()
{

	int score = 0;

	cout << "Please enter your score:" << endl;
	cin >> score;
	// Single line if statement: if (condition) {statement executed when the condition is met}
	if(score>=60){
		cout << "You passed" << endl;
	}
	
	// Multiline if statement: if (condition) {statement executed when the condition meets} else {statement executed when the condition does not meet}
	if(score>=60){
		cout << "You passed" << endl;
	}else{
		cout << "You failed" << endl;
	}
	
	// Multi conditional if statements: if (condition 1) {statements executed when condition 1 meets} else if (condition 2) {statements executed when condition 2 meets}... Else {statements executed when all conditions are not met}
	if(score>=90)
	{
		cout << "Excellent results" << endl;
	}
	else if(score>=60)
	{
		cout << "Pass the grade" << endl;
	}
	else
	{
		cout << "Fail" << endl;
	}
	
	// Nested if statements: if (condition 1) {if (condition 2) {if (condition 3) {}
	if(score>=60)
	{
		cout << "Pass the grade" << endl;
		if(score>=90)
		{
			cout << "Excellent results" << endl;
		}
	}
	else
	{
		cout << "Fail" << endl;
	}


	system("pause");

	return 0;
}

4.1.2 ternary operator

# include <iostream>
using namespace std;

int main()
{

	// Expression 1? Expression 2: expression 3;
	// If expression 1 is true, expression 2 is executed, otherwise expression 3 is executed
	// Maximum number of outputs
	int a = 10;
	int b = 20;
	int max = a>b?a:b;
	cout << max << endl;

	system("pause");

	return 0;
}

4.1.3 switch statement

# include <iostream>
using namespace std;

int main()
{

	// Multi conditional branch statement
	/*
	switch((expression)
	{
		case Result 1:
			Execute statements;
			break;
		case Result 2:
			Execute statements;
			break;
		case Result 3:
			Execute statements;
			break;
		case Result 4:
			Execute statements;
			break;
		...
		default:Execute statements; break;
	}
	*/

	system("pause");

	return 0;
}

4.2 circulation structure

Random number generated by the system:

//Time system time header file
# include <ctime>

// Add random number seeds and generate random numbers using the current system time to prevent the random numbers from being the same every time.
srand((unsigned int)time(NULL));

rand() % 100 + 1;
// rand() generates a random number
// Rand()% 100 generates random numbers from 0 to 99
// Rand()% 100 + 1 generates random numbers from 1 to 100

4.2.1 while loop statement

# include <iostream>
using namespace std;

int main()
{
	/*
	while(Cycle conditions)
	{
		Circular statement
	}
	*/

	system("pause");

	return 0;
}

4.2.2do... while loop statement

# include <iostream>
using namespace std;

int main()
{
	/*
	First execute the loop statement once, and then judge the loop.
	do
	{
		Loop statement;
	}
	while(Cycle conditions);
	*/

	system("pause");

	return 0;
}

4.2.3 for loop statement

# include <iostream>
using namespace std;

int main()
{
	/*
	for(Start expression; Conditional expression; End loop body)
	{
		Loop statement;
	}
	*/

	system("pause");

	return 0;
}

4.2.4 nested loops

# include <iostream>
using namespace std;

int main()
{
	/*
	for(Start expression; Conditional expression; End loop body)
	{
		Loop statement;
		for(Start expression; Conditional expression; End loop body)
		{
			Loop statement;
		}
	}
	*/

	system("pause");

	return 0;
}

4.3 jump statement

4.3.1 break statement

Jump out of selection structure or loop structure

• In the switch statement, the function is to terminate the case and jump out of the switch
• In the circular statement, the function is to jump out of the current circular statement
• Appears in a nested loop to jump out of the nearest inner loop statement

4.3.2 continue statement

Function: in a loop statement, skip the remaining unexecuted statements in this loop and continue to execute the next loop.

4.3.3 goto statement

Not recommended

# include <iostream>
using namespace std;

int main()
{
	/*
	Function: unconditional jump
	Usage: goto tag; When the goto statement is executed, if the name of the tag exists, it will jump to the location of the tag.
	*/
	cout << "first" << endl;
	goto FLAG;
	cout << "the second" << endl;
	cout << "Third" << endl;
	FLAG:
	cout << "Fourth" << endl;
	cout << "Fifth" << endl;
	cout << "Sixth" << endl;

	system("pause");

	return 0;
}

5. Array

An array is a collection of the same elements
characteristic:

• Each data element in the array is of the same data type.
• An array consists of contiguous memory locations.

5.1 one dimensional array

Definition of array

1. Data type array name [array length];
2. Data type array name [array length] = {value 1, value 2...};
3. Data type array name [] = {value 1, value 2...};

Purpose of array name

• You can count the length of the entire array in memory.
  • Sizeof (array name);
• You can get the first address of the array in memory.
  • (int) array name: This outputs the decimal first address.
  • Array name: This outputs the first hexadecimal address.
  • (int) & array name [0]: the address of the first element in the array. The address of the first element is the first address of the array.
• The array name is a constant and cannot be assigned.

5.2 two dimensional array

Array definition (the second is recommended)

1. Data type array name [number of rows] [number of columns];
2. Data type array name [number of rows] [number of columns] = {value 11, value 12...}, {value 21, value 22...}...};
3. Data type array name [number of rows] [number of columns] = {value 1, value 2, value 3, value 4, value 5...};
4. Data type array name [] [number of columns] = {value 1, value 2, value 3, value 4, value 5...};

Purpose of array name

• View the memory space occupied by the two-dimensional array
• Get the first address of two-dimensional array

6. Function

Function: encapsulate a piece of frequently used code to reduce code duplication. Large programs will be divided into several program blocks, and each module will realize specific functions.

6.1 definition of function

/*
Syntax:
Return value type function name (parameter list)
{
	Function body statement

	return expression
}
*/

6.2 function call

# include <iostream>
using namespace std;
// Function declaration: if the function to be called is defined after the function to be called, you need to declare the function.
int add(int num1,int num2);

int main()
{
	int a = 1;
	int b = 2;
	// When calling a function, the passed a and b have actual values, and they become arguments.
	int c = add(a, b);

	cout << "c=" << c << endl;

	system("pause");

	return 0;
}

// When defining, num1 and num2 have no real data. At this time, it is a formal parameter.
int add(int num1, int num2)
{
	int sum = num1 + num2;
	return sum;
}

Note: any change in the formal parameter in the function during value transfer will not affect the actual parameter value.

6.3 function sub file preparation

Function: make the code structure clearer
Steps:

• Create a header file with the suffix. h
• Create a source file with the suffix. cpp
• Write the declaration of the function in the header file
• Write the definition of the function in the source file

// swap.h
# include <iostream>
using namespace std;
// Declaration of function

void swap(int a, int b);

// swap.cpp
# include "swap.h"

void swap(int a, int b)
{
	int temp = a;
	a = b;
	b = temp;

	cout << "a = " << a << endl;
	cout << "b = " << b << endl;

}

// The main function is called the source file
# include <iostream>
# include "swap.h"
// It is written by yourself to use double quotation marks, and it is written by others to use angle brackets.
using namespace std;

int main()
{
	int a = 1;
	int b = 2;
	
	swap( a, b);

	system("pause");

	return 0;
}

7. Pointer

Function: indirect access to memory through pointer.

7.1 definition and use of pointer

# include <iostream>
using namespace std;

int main()
{
	// Define pointer
	int a = 10;
	// Syntax of pointer definition: data type * pointer variable name;
	int * p;
	//Pointer variable records the address of variable a
	p = &a;
	// Use pointer
	cout << "a Your address is:" << &a << endl;
	cout << "a Your address is:" << p << endl;
	// You can find the memory stored value pointed to by the pointer by dereference.
	cout << "Pointer p Points to the value stored in the memory space" << *p << endl;
	// You can change the value stored in the specified memory space in this way
	*p = 100;
	cout << "a = " << a << endl;
	cout << "*P = " << *p << endl;
	
	system("pause");

	return 0;
}

In the 32-bit operating system, the memory space occupied by pointers is fixed at 4 bytes, and in the 64 bit operating system, it is 8 bytes (whether int, double... All types of pointers are the same)

7.2 null pointer and wild pointer

Null pointer: pointer variable points to the space numbered 0 in memory.
Purpose: initialize pointer variables.
Note: the memory pointed to by the null pointer is inaccessible.

Wild pointer: pointer variable points to illegal memory space. Avoid wild pointer in the program.

// Define null pointer
int *p = NULL;

// Define field pointer
int *p = (int *)0x1234;
// 0x1234 this memory space is not owned by itself and has no permission to operate it.

7.3 const modifier pointer

const modifies pointers in three ways:

1. const modifier pointer: constant pointer.
2. const modifier constant: pointer constant.
3. const modifies both pointers and constants.

/*
const pointer 
Features: the pointer can be modified, but the value pointed to by the pointer cannot be modified.
*/
const int * p = &a;
/*
constant pointer 
Features: the pointer cannot be modified, and the value pointed by the pointer can be modified.
*/
int * const p = &a;
/*
const That is, it modifies both pointers and constants
 Features: the pointing of the pointer cannot be modified, and the value pointed by the pointer cannot be modified.
*/
const int * const p = &a;

7.4 joint use of pointer, array and function

# include <iostream>
using namespace std;

void swap(int * p1, int * p2)
{
	int temp = *p1;
	*p1 = *p2;
	*p2 = temp;
}

int main()
{
	int arr[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

	// Using pointers to access elements in an array
	int *p = arr;  // arr is the first address of the array
	cout << "Accessing the first element with a pointer:" << *p << endl;
	p++; // Let the pointer back 4 bytes, and the pointer points to the second element.
	cout << "Accessing the second element with a pointer:" << *p << endl;

	cout << "Traverse the array with a pointer:" << endl;
	// Using pointers to facilitate arrays
	int * p2 = arr;
	for (int i = 0; i < 10; i++)
	{
		cout << *p << endl;
		p++;
	}
	
	//Address passing will change the argument value
	int a = 10;
	int b = 20;

	swap(&a, &b);

	cout << "After exchange a:" << a << endl;
	cout << "After exchange b:" << b << endl;
	
	system("pause");

	return 0;

}

// Encapsulates a function that uses bubble sorting to sort an integer array in ascending order
# include <iostream>
using namespace std;

void bubbleSort(int * arr, int len)
{
	for(int i = 0; i < len - 1; i++)
	{
		for(int j = 0; j < len - i - 1; j++)
		{
			if(arr[j] > arr[j+1])
			{
				int temp = arr[j];
				arr[j] = arr[j+1];
				arr[j+1] = temp;	
			}
		}
	}
}


int main()
{
	int arr[10] = {4, 3, 6, 9, 1, 2, 7, 5, 8};
	bubbleSort(arr, 9);
	
	system("pause");

	return 0;
}

8. Structure

Structures are user-defined data types, allowing users to store different data types

8.1 definition and use of structure

Syntax: struct structure name {structure member list};
There are three ways to create variables through structures:

• struct structure name variable name
• struct structure name variable name = {member 1 value, member 2 value...}
• When you define a structure, you create variables

#include <iostream>
using namespace std;
#include <string>
struct Student
{
	string name;
	int age;
	int score;
}s3;
// Create variables when defining structures

int main()
{
	// The struct keyword can be omitted when creating variables
	struct Student s1;
	s1.name = "Zhang San";
	s1.age = 15;
	s1.score = 90;

	struct Student s2 = {"Li Si", 16, 89};
	
	s3.name = "Wang Wu";
	s3.age = 16;
	s3.score = 91;
	
	system("pause");

	return 0;
}

Structure array: struct structure name array name [number of elements] = {}, {}, {},...}

8.2 structure pointer

Accessing members in a structure through a pointer

• Using the operator - > you can access structure properties through the structure pointer

#include <iostream>
using namespace std;
#include <string>
struct Student
{
	string name;
	int age;
	int score;
};

int main()
{
	// Create student structure variable
	Student s = {"Zhang San", 18, 100};

	// Pointer to structure variable
	Student *p = &s;
	
	// Accessing data in structure variables through pointers
	cout << "full name:" << p->name << "Age:" << p->age << "fraction:" << p->score << endl; 
	
	system("pause");

	return 0;
}

8.3 structure nested structure

#include <iostream>
using namespace std;
#include <string>

struct Student
{
	string name;
	int age;
	int score;
};

struct Teacher
{
	int id;
	string name;
	int age;
	struct Student stu;
};

int main()
{
	// Create teacher
	Teacher t;
	t.id = 100;
	t.name = "Lao Wang";
	t.age = 50;
	t.stu.name = "Xiao Wang";
	t.stu.age = 18;
	t.stu.score = 89;
	
	cout << "Teacher's name:" << t.name << "Teacher's age:" << t.age << "Teacher's number:" << t.id << << "Teacher's Student Name:" << t.stu.name << "Age of teacher's students:" << t.stu.age << "Teacher's student performance:" << t.stu.score << endl; 
	
	system("pause");

	return 0;
}

8.4 structure as function parameter

• pass by value
• Address delivery

As with ordinary parameters, value passing only passes values, and changing formal parameters does not change arguments.

8.5 const usage scenario in structure

Function: prevent misoperation

#include <iostream>
using namespace std;
#include <string>
struct Student
{
	string name;
	int age;
	int score;
};

void printStudents(const Student * s)
{
	//S - > age = 100; / / after using const modification, an error will be reported once the operation is modified, which can prevent misoperation.
	// Here, if you don't use address transfer and directly use value transfer, even if you modify it, it won't change the value of the most original data. Why not?
	    // Because if you use value passing, you need to re open up an address space. If the amount of data passed is too large, it will consume a lot of space. If you use address passing, you only need to open up a pointer space.
	cout << "Student Name:" << s->name << " Age:" << s->age << " fraction:" << s->score << endl; 
}

int main()
{
	// Create student structure variable
	Student s = {"Zhang San", 18, 100};

	printStudents(s);
	
	cout << "full name:" << s.name << "Age:" << s.age << "fraction:" << s.score << endl; 
	
	system("pause");

	return 0;
}