Basic operation and process control 2

  One .  Basic operation

（ One ）. data type  

1.  Basic data type

      a. plastic ：byte（ byte ） short（ Short plastic surgery ）  int（ plastic ） long（ Long plastic surgery ）

      b. floating-point ：float（ Single precision ）   double（ Double precision ）

      c. Boolean type ：bool

      d. Character ：char

2. Reference data type  

string（ character string ）  Array    class    Interface

（ Two ）. Variables and constants  

1. Definition

      Variable ：

               a. It refers to the amount that can change at any time during the operation of the program

               b. The amount used to store a change   A storage unit in memory
               c. Access to variable names is access to variable values
               d. Each variable is allocated a space to store its own value , And the space occupied by different types is different

      Constant ：

               a. It refers to the variables that will not change during the operation of the program  

               b. By declaring and initializing Variable when , Add in front const keyword , You can put this Variable Designated as Constant  

               c. Constants must be initialized at declaration time . After specifying its value , You can't change it any more

               d. The value of a constant must be available for calculation at compile time . therefore , You cannot initialize a constant with a value extracted from a variable                         The amount . If it needs to be done , Read only fields should be used

2. Format     

             Variable = type + Variable name  

            Hump nomenclature

3. Type conversion

  （1. Transformation types ： Implicit 、 mandatory （ Basic types ）

         a. Implicit ： From low to high        byte-->short(char)-->int-->long-->float-->double

         b. mandatory ： From high to low        byte<--short(char)<--int<--long<--float<--double

    (2). Format ：（ Force conversion of data types ） Variable name

       // Define an integer variable and assign a value , Then it is transformed into a single precision variable

        int a = 10;

        float b;

        b = a;

        print(a+"\t"+b);  //10 

        // Define a single precision variable and assign a value , Then it is transformed into a shaping variable

        float x = 2.5f;

        int y;

        y = (int)x;// Forced type conversion

        print(y);  //2

        //ASCII code ：char（a:97  A:65）

        // Define a character variable and an integer variable and assign values to them , And then do the addition （ The result is an integer or character ）

        int m = 2, n;

        char p = 'd',q;

        n = m + p;

        print(n);    //102

        q = (char)(m + p);

        print(q);   //f

        // Define a string variable , Then it is transformed into shaping

        string s = "123"; 

        int a = int.Parse(s);// Convert a string into an integer

        //Parse Method can convert a string type variable into a basic type variable   

4. Console input and output

Console.WriteLine();

Console.ReadLine();

5. Escape character

enter ：\n

Horizontal tabs （ When printing multiple variables , The space between them ）：\t

（ 3、 ... and ）. Basic operation

    1. + - * / %

      use / Do calculations , If there is a floating point in the operand , Then the result must be floating point

    2. Relational operator ：>  >=  <  <=  ==  !=

    3. Self increasing 1：++    Self reduction 1：--

                   a++ or a-- ：  Use first and then add and subtract  

                  ++a or --a ：  Add and subtract before using

    4. Logical operators ：

                            Logic and ：&&    The whole is true , False, false

                            Logic or ： ||      There are really true , All false is false

                            Logic is not ：！    1 change 0   0 change 1

   5. Three yuan （ Objective ） Operator ： 

        expression 1? expression 2： expression 3;

        int m = 1, n = 2, p;

        p = m > n ? 1 : 0;

6.VS Shortcut keys commonly used in  

       Ctrl + s preservation

       Ctrl + c Copy

       Ctrl + v Paste

       Ctrl + x shear

       Ctrl + z revoke

　　Ctrl + k +d Quick alignment code

　　Ctrl + k + c Quick comment selection

　　Ctrl + k + u Quickly cancel the selected comment content

Two . Process control

（ One ）. The order

                     Read from top to bottom

（ Two ）. Judge

         1.if 

         2.switch

（ 3、 ... and ）. loop

         1. for

             for( expression 1; expression 2; expression 3)   {     // Loop body statement     }

             for The expression of 3 Must be implemented

         2. while 

              expression 1

             while( expression 2）{  Loop body statement ;    expression 3;     }

         3. do...while

              do

              {      sentence ;  // Execute before judge    }

              while( The loop condition ）

             while and while The difference between ：

              a. Execution order is different

              b.  When conditions are not met while The loop will not execute once and do while  At least once

         4.continue

             Used inside the loop body , End this cycle , Start a new cycle

         5.break

         a. Jump out of Switch loop , Carry on switch The following statement   Generally used for swile In structure and cyclic structure
         b. Terminate a program , Continue to execute the statement after the loop , If there are multiple loops , Just jump out Break This layer of circulation
         c. and if Use it together ： Meet a certain condition , Jump out of current loop