Start
Types, variables, expressions, statements, functions
init main()
{
return 0;
}
Function definition: return type, function name, (parameter list), function body
Compile and run the program
translater
input Output
IO mechanism
iostream library
Standard input cin
Standard output cout
Standard error cerr
clog
head File
#include <iostream>
Output operator <<
Accepts two operands, the left side must be an ostream object, and the right side is the value to be printed
Returns the operand on the left
Operator endl ends the current line
std namespace
::Scope operator
Prefix increment operator++
++ val val = val + 1;
for statement
Loop head
Initialization statement (executed only once at the entrance of the for loop), loop condition, expression
Read variable input data
while(std:cin<<val)
Detect std::cin
Use the istream object as a condition to detect the stream state, and when the end of file is encountered, invalid input (not a number)
class
Usually use .h as the suffix of the header file
Use class types that are as natural as built-in types
Sales_item item;
item is an object of type Sales_item, an object of type Sales_item
Member functions: methods
. Members of Class Type Objects
C++ basics
2. Variables and basic types
2.1 Basic built-in types
-
Arithmetic type
-
Void type
2.1.1 Arithmetic types
| Types of | meaning | smallest size |
|---|---|---|
| bool | ||
| char | character | 8 |
| int | Integer | |
| float |
Signed and unsigned types
Signed type can represent positive and negative numbers, 0
Unsigned types can only represent numbers greater than 0 unsigned
2.1.2 Type conversion
unsigned char c=-1;
char occupies 8bit, the value of c is 255
Assign an unsigned type a value outside the range, the actual result is the remainder after modulo 256
The first bit of the binary number is the symbol mark
signed char c2=256;
c2 is undefined
When assigning a signed type to a value beyond the range of her representation,