구차니의 잡동사니 모음

pi@raspberrypi ~ $ sudo cat /etc/default/keyboard

# KEYBOARD CONFIGURATION FILE

# Consult the keyboard(5) manual page.

XKBMODEL="pc105"

XKBLAYOUT="gb"

XKBVARIANT=""

XKBOPTIONS=""

BACKSPACE="guess" 

pi@raspberrypi ~ $ sudo setupcon

We are not on the console, the console is left unconfigured. 

} 

$ ./a.out

#include <stdint.h>를 넣지 않으면 에러가 발생한다.

$ gcc size.c

size.c: In function ‘main’:

size.c:6:2: error: unknown type name ‘int64_t’

These -m switches are supported in addition to the above on AMD x86-64 processors in 64-bit environments.

-m32

-m64

Generate code for a 32-bit or 64-bit environment. The 32-bit environment sets int, long and pointer to 32 bits and generates code that runs on any i386 system. The 64-bit environment sets int to 32 bits and long and pointer to 64 bits and generates code for AMD's x86-64 architecture. 

[링크 : https://gcc.gnu.org/onlinedocs/gcc-3.1/gcc/i386-and-x86-64-Options.html]

$ gcc -m32 void.c

In file included from /usr/include/stdio.h:28:0,

                 from void.c:1:

/usr/include/features.h:324:26: fatal error: bits/predefs.h: No such file or directory

compilation terminated.

$ sudo apt-get install gcc-multilib

[링크 : http://uce.uniovi.es/tips/Programming/Cpp/forc32bitscompilation.html] 

[링크 : http://stackoverflow.com/questions/22355436/how-to-compile-32-bit-apps-on-64-bit-ubuntu]

$ gcc -v

Using built-in specs.

COLLECT_GCC=gcc

COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6/lto-wrapper

Target: x86_64-linux-gnu

Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu

Thread model: posix

gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) 

$ vi void.c

#include <stdio.h>

void main()

{

        void *fp;

        int a = 0;

        fp = &a;

        printf("sizeof(void) %d\n",sizeof(void));

        fp++;

        printf("fp %8X\n",fp);

} 

$ gcc void.c

void.c: In function ‘main’:

void.c:9:2: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘long unsigned int’ [-Wformat]

void.c:10:2: warning: format ‘%X’ expects argument of type ‘unsigned int’, but argument 2 has type ‘void *’ [-Wformat]

void.c:12:2: warning: format ‘%X’ expects argument of type ‘unsigned int’, but argument 2 has type ‘void *’ [-Wformat]

6.23 Arithmetic on void- and Function-Pointers

In GNU C, addition and subtraction operations are supported on pointers to void and on pointers to functions. This is done by treating the size of a void or of a function as 1.

A consequence of this is that sizeof is also allowed on void and on function types, and returns 1.

The option -Wpointer-arith requests a warning if these extensions are used.

[링크 : https://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html]

Compiler Error CS0242

The operation in question is undefined on void pointers

Incrementing a void pointer is not allowed. For more information, see Unsafe Code and Pointers (C# Programming Guide).

[링크 : https://msdn.microsoft.com/en-us/library/dhyat531(v=vs.90).aspx] 

4.3.3 ‘Implicit CR in every LF’

Most servers send two control characters, CR and LF, to start a new line of the screen. The CR character makes the cursor return to the left-hand side of the screen. The LF character makes the cursor move one line down (and might make the screen scroll).

Some servers only send LF, and expect the terminal to move the cursor over to the left automatically. If you come across a server that does this, you will see a stepped effect on the screen, like this:

First line of text
                  Second line
                             Third line

If this happens to you, try enabling the ‘Implicit CR in every LF’ option, and things might go back to normal:

First line of text
Second line
Third line

4.3.4 ‘Implicit LF in every CR’

Most servers send two control characters, CR and LF, to start a new line of the screen. The CR character makes the cursor return to the left-hand side of the screen. The LF character makes the cursor move one line down (and might make the screen scroll).

Some servers only send CR, and so the newly written line is overwritten by the following line. This option causes a line feed so that all lines are displayed.

[링크 : http://tartarus.org/~simon/putty-snapshots/htmldoc/Chapter4.html]

Voltage: 4.75-5.25V

Working Frequency: 125 KHz

Sensing Distance(Max): 70mm

TTL Output: 9600 baudrate, 8 data bits, 1 stop bit, and no verify bit

Wiegand Output: 26 bits Wiegand format, 1 even verify bit, 24 data bits, and 1 odd verify bit

[링크 : http://www.seeedstudio.com/wiki/Grove_-_125KHz_RFID_Reader] 

125Khz  EM카드

저렴하고 광범위하게 사용되고 있는카드

13.56Mhz MF카드

카드의 데이터값을 수정할 수 있으며

교통카드가 대표적인 MF카드임.

[링크 : http://korearfidtag.com/]