C cout hex values

Question

I want to do   int a   255   cout  lt  lt  a    and have it show FF in the output  how would I do this

User · Answer

If you want to print a single hex number  and then revert back to decimal you can use this   std  cout  lt  lt  std  hex  lt  lt  num  lt  lt  std  dec  lt  lt  std  endl

User · Answer

To manipulate the stream to print in hexadecimal use the hex manipulator   cout  lt  lt  hex  lt  lt  a    By default the hexadecimal characters are output in lowercase  To change it to uppercase use the uppercase manipulator   cout  lt  lt  hex  lt  lt  uppercase  lt  lt  a    To later change the output back to lowercase  use the nouppercase manipulator   cout  lt  lt  nouppercase  lt  lt  b

User · Answer

Use    include  lt iostream gt        std  cout  lt  lt  std  hex  lt  lt  a    There are many other options to control the exact formatting of the output number  such as leading zeros and upper lower case

User · Answer

std  hex is defined in  lt ios gt  which is included by  lt iostream gt   But to use things like std  setprecision std  setw std  setfill etc you have to include  lt iomanip gt

User · Answer

If you want to print a single hex number  and then revert back to decimal you can use this   std  cout  lt  lt  std  hex  lt  lt  num  lt  lt  std  dec  lt  lt  std  endl

User · Answer

How are you   include  lt iostream gt   include  lt iomanip gt   unsigned char buf0      4  85  250  206   for  int i   0 i  lt  sizeof buf0   sizeof buf0 0   i          std  cout  lt  lt  std  setfill  0                   lt  lt  std  setw 2                  lt  lt  std  uppercase                 lt  lt  std  hex  lt  lt   0xFF  amp  buf0 i    lt  lt   quot   quot

User · Answer

std  hex is defined in  lt ios gt  which is included by  lt iostream gt   But to use things like std  setprecision std  setw std  setfill etc you have to include  lt iomanip gt

User · Answer

Use std  uppercase and std  hex to format integer variable a to be displayed in hexadecimal format    include  lt iostream gt  int main        int a   255         Formatting Integer    std  cout  lt  lt  std  uppercase  lt  lt  std  hex  lt  lt  a  lt  lt  std  endl     Output  FF    std  cout  lt  lt  std  showbase   lt  lt  std  hex  lt  lt  a  lt  lt  std  endl     Output  0XFF    std  cout  lt  lt  std  nouppercase  lt  lt  std  showbase   lt  lt  std  hex  lt  lt  a  lt  lt  std  endl     Output  0xff     return 0

User · Answer

I understand this isn t what OP asked for  but I still think it is worth to point out how to do it with printf  I almost always prefer using it over std  cout  even with no previous C background    printf    2X   a      2  defines the precision   X  or  x  defines case

User · Answer

There are different kinds of flags  amp  masks you can use as well  Please refer http   www cplusplus com reference iostream ios base setf  for more information    include  lt iostream gt  using namespace std   int main         int num   255      cout setf ios  hex  ios  basefield       cout  lt  lt   Hex     lt  lt  num  lt  lt  endl       cout unsetf ios  hex       cout  lt  lt   Original format     lt  lt  num  lt  lt  endl       return 0

User · Answer

std  hex gets you the hex formatting  but it is a stateful option  meaning you need to save and restore state or it will impact all future output   Naively switching back to std  dec is only good if that s where the flags were before  which may not be the case  particularly if you re writing a library    include  lt iostream gt   include  lt ios gt        std  ios base  fmtflags f  cout flags          save flags state std  cout  lt  lt  std  hex  lt  lt  a  cout flags  f        restore flags state   This combines Greg Hewgill s answer and info from another question

User · Answer

Use    include  lt iostream gt        std  cout  lt  lt  std  hex  lt  lt  a    There are many other options to control the exact formatting of the output number  such as leading zeros and upper lower case

User · Answer

How are you   include  lt iostream gt   include  lt iomanip gt   unsigned char buf0      4  85  250  206   for  int i   0 i  lt  sizeof buf0   sizeof buf0 0   i          std  cout  lt  lt  std  setfill  0                   lt  lt  std  setw 2                  lt  lt  std  uppercase                 lt  lt  std  hex  lt  lt   0xFF  amp  buf0 i    lt  lt   quot   quot

User · Answer

Use    include  lt iostream gt        std  cout  lt  lt  std  hex  lt  lt  a    There are many other options to control the exact formatting of the output number  such as leading zeros and upper lower case

User · Answer

std  hex gets you the hex formatting  but it is a stateful option  meaning you need to save and restore state or it will impact all future output   Naively switching back to std  dec is only good if that s where the flags were before  which may not be the case  particularly if you re writing a library    include  lt iostream gt   include  lt ios gt        std  ios base  fmtflags f  cout flags          save flags state std  cout  lt  lt  std  hex  lt  lt  a  cout flags  f        restore flags state   This combines Greg Hewgill s answer and info from another question

User · Answer

I understand this isn t what OP asked for  but I still think it is worth to point out how to do it with printf  I almost always prefer using it over std  cout  even with no previous C background    printf    2X   a      2  defines the precision   X  or  x  defines case

User · Answer

Use    include  lt iostream gt        std  cout  lt  lt  std  hex  lt  lt  a    There are many other options to control the exact formatting of the output number  such as leading zeros and upper lower case

User · Answer

C  20 std  format This is now the cleanest method in my opinion  as it does not pollute std  cout state with std  hex  main cpp  include  lt format gt   include  lt string gt   int main         std  cout  lt  lt  std  format  quot   x     x     n quot   16  17  18      Expected output  10 0x11 18  Not yet implemented on GCC 10 0 1  Ubuntu 20 04  But the awesome library that became C  20 and should be the same worked once installed with  git clone https   github com fmtlib fmt cd fmt git checkout 061e364b25b5e5ca7cf50dd25282892922375ddc mkdir build cmake    sudo make install  main2 cpp  include  lt fmt core h gt   include  lt iostream gt   int main         std  cout  lt  lt  fmt  format  quot   x     x     n quot   16  17  18      Compile and run  g   -ggdb3 -O0 -std c  11 -Wall -Wextra -pedantic -o main2 out main2 cpp -lfmt   main2 out  Documented at   https   en cppreference com w cpp utility format format https   en cppreference com w cpp utility format formatter Standard format specification  More info at  std  string formatting like sprintf Pre-C  20  cleanly print and restore std  cout to previous state main cpp  include  lt iostream gt   include  lt string gt   int main         std  ios oldState nullptr       oldState copyfmt std  cout       std  cout  lt  lt  std  hex      std  cout  lt  lt  16  lt  lt  std  endl      std  cout copyfmt oldState       std  cout  lt  lt  17  lt  lt  std  endl     Compile and run  g   -ggdb3 -O0 -std c  11 -Wall -Wextra -pedantic -o main out main cpp   main out  Output  10 17  More details  Restore the state of std  cout after manipulating it Tested on GCC 10 0 1  Ubuntu 20 04

User · Answer

There are different kinds of flags  amp  masks you can use as well  Please refer http   www cplusplus com reference iostream ios base setf  for more information    include  lt iostream gt  using namespace std   int main         int num   255      cout setf ios  hex  ios  basefield       cout  lt  lt   Hex     lt  lt  num  lt  lt  endl       cout unsetf ios  hex       cout  lt  lt   Original format     lt  lt  num  lt  lt  endl       return 0

User · Answer

Use std  uppercase and std  hex to format integer variable a to be displayed in hexadecimal format    include  lt iostream gt  int main        int a   255         Formatting Integer    std  cout  lt  lt  std  uppercase  lt  lt  std  hex  lt  lt  a  lt  lt  std  endl     Output  FF    std  cout  lt  lt  std  showbase   lt  lt  std  hex  lt  lt  a  lt  lt  std  endl     Output  0XFF    std  cout  lt  lt  std  nouppercase  lt  lt  std  showbase   lt  lt  std  hex  lt  lt  a  lt  lt  std  endl     Output  0xff     return 0

User · Answer

std  hex is defined in  lt ios gt  which is included by  lt iostream gt   But to use things like std  setprecision std  setw std  setfill etc you have to include  lt iomanip gt

User · Answer

To manipulate the stream to print in hexadecimal use the hex manipulator   cout  lt  lt  hex  lt  lt  a    By default the hexadecimal characters are output in lowercase  To change it to uppercase use the uppercase manipulator   cout  lt  lt  hex  lt  lt  uppercase  lt  lt  a    To later change the output back to lowercase  use the nouppercase manipulator   cout  lt  lt  nouppercase  lt  lt  b

User · Answer

std  hex is defined in  lt ios gt  which is included by  lt iostream gt   But to use things like std  setprecision std  setw std  setfill etc you have to include  lt iomanip gt

User · Answer

C  20 std  format This is now the cleanest method in my opinion  as it does not pollute std  cout state with std  hex  main cpp  include  lt format gt   include  lt string gt   int main         std  cout  lt  lt  std  format  quot   x     x     n quot   16  17  18      Expected output  10 0x11 18  Not yet implemented on GCC 10 0 1  Ubuntu 20 04  But the awesome library that became C  20 and should be the same worked once installed with  git clone https   github com fmtlib fmt cd fmt git checkout 061e364b25b5e5ca7cf50dd25282892922375ddc mkdir build cmake    sudo make install  main2 cpp  include  lt fmt core h gt   include  lt iostream gt   int main         std  cout  lt  lt  fmt  format  quot   x     x     n quot   16  17  18      Compile and run  g   -ggdb3 -O0 -std c  11 -Wall -Wextra -pedantic -o main2 out main2 cpp -lfmt   main2 out  Documented at   https   en cppreference com w cpp utility format format https   en cppreference com w cpp utility format formatter Standard format specification  More info at  std  string formatting like sprintf Pre-C  20  cleanly print and restore std  cout to previous state main cpp  include  lt iostream gt   include  lt string gt   int main         std  ios oldState nullptr       oldState copyfmt std  cout       std  cout  lt  lt  std  hex      std  cout  lt  lt  16  lt  lt  std  endl      std  cout copyfmt oldState       std  cout  lt  lt  17  lt  lt  std  endl     Compile and run  g   -ggdb3 -O0 -std c  11 -Wall -Wextra -pedantic -o main out main cpp   main out  Output  10 17  More details  Restore the state of std  cout after manipulating it Tested on GCC 10 0 1  Ubuntu 20 04

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