Write simple switch (a) in C

　// This is the note, record the first day

#include <stdio.h>

/*
head File
    stdio refers to "standard input & output" (standard output)
Therefore, when the source code is used as the standard input and output functions, it must include the header!
E.g. c language printf ( "% d", i); function or the like; scanf ( "% d", & i).

In double quotation marks header files, which means looking for this header file to find in the same directory as the following
include "test.h"

*/

int main(void)
{
    printf ( " --- switch background management ---- \ the n- " );
    printf ( " login \ the n- " );
    printf ( " Create an account \ the n- " );
    printf ( " delete account \ the n- " );
    printf ( " Exit \ the n- " );
    printf ( " Name:% s martial art:% s force value:% d \ the n- " , " Joe Smith crazy " , " non-partisan " , 89 );    
    the printf ( " Pi:% 20f \ n-. " , 3.1415926 );

    return 0;
}

/*
main function

    mian is the single entry program, a program can have only one main function

    the main function returns an int integer

    General usage:
        Program ended successfully, with the main function returns 0
        Program ends abnormally, the main function returns with a number greater than 0
*/

/*
Line breaks and tabs
    \ N newline
    \ T Tab: text may be aligned vertically
*/

/*
printf () function call format is: printf ( "<format string>", <argument list>).
    % S% c and commonly used in like printf, sprintf string formatting functions, parameters for formatting the data type is determined. The printf ( "% s", a) will be a variable
        Formatted string type.
*/
  
/*
The format specification "%" and formatting characters representing the data output from the converter to the specified output format. Format Description always by the "%" character began.
    %% percent sign printed, are not converted.
    % C integer converted to the corresponding ASCII characters.
    % D converted to decimal integer.
    % F converted into double precision floating point number, i.e. after the decimal point 6
    % .20f after the decimal point indicates accurate to 20
    20% 20f represents a placeholder, starting from the right, no digital place filled with spaces
    % O Integer into octal.
    % S Integer translated into strings.
    % X an integer to lower case hexadecimal.
    % X Integer to uppercase hex.
    % X output integer in hexadecimal form, or the address of the output string.
    % U unsigned decimal number to the data type (unsigned). Note: d% u whether a value range of symbols, that is, the value of% limit, otherwise the value will be printed out by mistake.
    % E real output exponentially,
    % G automatically selected f or e format depending on the size format, does not output the zero meaningless.
*/