Why use the output controller:

• We know that the data in the computer is stored in the form of binary, but the code composed of 01 can represent both data and instructions. It's easy to misunderstand if you don't use the output controller to become what you want.

• If the 01 code represents data, then different output formats of the same 01 code combination will have different output results. So you need to use the output controller

Common output controllers include the following:

%d --------------- int

%ld --------------- long int

%c --------------- char

%f --------------- float

%lf --------------- double

%X (or% x, the latter% ාX) ---- integer (length is OK) (use hex output)

%o ------------ integer (length is OK) (octal output)

%s ------------ string

Code demo

/*

  ----------------2020/3/13 21:45---------------
 
  Objective: To explore the non - binary control output character

*/
# include<stdio.h>
int main(void)
{
    int i=10;
    char a='a';
    float b=2.123459789;
    double c=3.123456789;

    //%d is generally used for int type. Indicates output in decimal
    printf("%d\n",i);

    //%ld for long int type
    printf("%d\n",i);

    //%c for output string
    printf("%c\n",a);

    //%f is used to output single precision floating-point numbers
    printf("%f\n" ,b);

    //%lf is used to output double precision floating point numbers
    printf("%lf\n" ,c);

    
    return 0;
}
/*

--------------------vc++6.0 Results of running on------------------
10
10
a
2.123460
3.123457
---------------------------------------------------------

Experience:

  We can see that the output of floating-point number is up to six decimal places, both single precision and double precision are the same.
  Floating point numbers that exceed six digits are rounded off from the seventh digit. No matter how large the eighth digit is, the number after the seventh digit has nothing to do with it. It only depends on whether the seventh digit is rounded
  Floating point numbers less than six digits are followed by 0

*/

Hexadecimal output controller

• Code demo

/*

  -----------------2020/3/13 22:35----------------
  Objective:
  On the control of base output character

*/
# include<stdio.h>
int main(void)
{
    int i=30;

    //Output in octal
    printf("%o\n",i); //Enter the lowercase o
    printf("%O\n",i); //Uppercase O entered
    printf("%0\n",i);   //Number zero entered
    printf("%#o\n",i); / / enter the pound sign and lowercase letter o
    printf("%#O\n",i);
    
    printf("----------------\n");

    //Hex output
    printf("%x\n",i); //Enter lowercase x
    printf("%X\n",i); //The input is an uppercase X
    printf("%#x\n",i); / / enter the pound sign and lowercase o
    printf("%#X\n",i); / / enter the pound sign and lowercase o
    return 0;

}
/*

---------vc++6.0 Results of running in--------------
36
O

036
O
----------------
1e
1E
0x1e
0X1E
------------------------------------------

  Experience:
  
  Write o in octal to output an unsigned octal number. O in uppercase looks like zero, but o in uppercase is zero. And the number 0 is a blank line
  So in octal, only lowercase o can output data, andාo can output signed octal numbers

  In hexadecimal case x can output data. X outputs more than 10 uppercase characters. Lowercase must be lowercase characters. #X signed hexadecimal number.

  The reason why case can be output in hexadecimal and only lowercase can be output in octal may be because more than 10 parts of hexadecimal are represented by letters. Case can be used. Octal numbers are not case sensitive

*/
}