Learning records of programming -- Lesson 2 [first knowledge of C language]

Constant

1. Literal constants , Such as π.2.const Defined constant , Has constant properties , But it's actually a variable .

3. Constant of identifier Such as #define #define tall 186,4. Enumeration constants enum（ Enumerate keywords ）.

Escape character

\0 End flag for string printing . When initializing an array , If array element is a string , You need to bring \0.

\ddd Express 1-3 Eight digit octal number , Octal digit range 0-8.\xdd Represents two hexadecimal digits .

The operator

In front of ++, Say first ++, Post assignment , After ++, Indicates assignment first , after ++.

example a=10,b=++a, obtain a=b=11, if b=a++, be b=10,a=11.

scanf The value returned by the function is the number of characters entered , Writable loop while( scanf("%d",&A)!=EOF), Indicates that the number of characters entered meets the requirements ,EOF The value of is -1.

Cast

（ type ） You can implement cast for example int m=（int）3.1415, Put floating-point numbers 3.1415 Cast to integer .

Conditional operators

exp1？exp2：exp3, example (a>b)?a:b, Said when a>b Output when the condition is true a value , Otherwise output b value .