Converting an integer to binary in C

Question

I m trying to convert an integer 10 into the binary number 1010    This code attempts it  but I get a segfault on the strcat     int int to bin int k       char  bin      bin    char   malloc sizeof char       while k gt 0          strcat bin  k 2         k   k 2        bin    char   realloc bin  sizeof char     sizeof bin  1            bin sizeof bin -1      0       return atoi bin       How do I convert an integer to binary in C

User · Answer

You can use function this function to return char* with string representation of the integer:

   char* itob(int i) {
      static char bits[8] = {'0','0','0','0','0','0','0','0'};
      int bits_index = 7;
      while ( i > 0 ) {
         bits[bits_index--] = (i & 1) + '0';
         i = ( i >> 1);
      }
      return bits;
   }

It's not a perfect implementation, but if you test with a simple printf("%s", itob(170)), you'll get 01010101 as I recall 170 was. Add atoi(itob(170)) and you'll get the integer but it's definitely not 170 in integer value.

User · Answer

You can add the functions to the standard library and use it whenever you need  Here is the code in C    include  lt stdio h gt   int power int x  int y    calculates x y    int product   1  for  int i   0  i  lt  y  i          product   product   x    return  product     int gpow bin int a    highest power of 2 less equal to than number itself    int i  z  t  for  i   0   i          t   power 2  i       z   a   t      if  z    0                break          return  i - 1     void bin write int x      printf  quot  d quot   1   int current power   gpow bin x   int left   x - power 2  current power   int lower power   gpow bin left   for  int i   1  i  lt  current power - lower power  i          printf  quot 0 quot      if  left    0        printf  quot  d quot   1       bin write left       void main       printf  quot  d quot   gpow bin 67    int user input  printf  quot Give the input    quot    scanf  quot  d quot    amp user input   printf  quot  d quot   1   bin write user input

User · Answer

Just use itoa to convert to a string  then use atoi to convert back to decimal   unsigned int to int unsigned int k        char buffer 65      any number higher than sizeof unsigned int  bits per byte 8         return atoi  itoa k  buffer  2

User · Answer

The working solution for Integer number to binary conversion is below   int main         int num 241    Assuming 16 bit integer     for int i 15  i gt  0  i--  cout lt  lt   num  gt  gt  i   amp  1       cout lt  lt endl      for int i 0  i lt 16  i    cout lt  lt   num  gt  gt  i   amp  1       cout lt  lt endl      return 0      You can capture the cout lt  lt  part based on your own requirement

User · Answer

You need to initialise bin  e g   bin   malloc 1   bin 0      0     or use calloc   bin   calloc 1  1     You also have a bug here    bin    char   realloc bin  sizeof char     sizeof bin  1      this needs to be    bin    char   realloc bin  sizeof char     strlen bin  1       i e  use strlen  not sizeof    And you should increase the size before calling strcat   And you re not freeing bin  so you have a memory leak   And you need to convert 0  1 to  0    1    And you can t strcat a char to a string   So apart from that  it s close  but the code should probably be more like this  warning  untested      int int to bin int k       char  bin     int tmp      bin   calloc 1  1      while  k  gt  0             bin   realloc bin  strlen bin    2         bin strlen bin  - 1     k   2     0         bin strlen bin       0         k   k   2          tmp   atoi bin      free bin      return tmp

User · Answer

If you want to transform a number into another number  not number to string of characters   and you can do with a small range  0 to 1023 for implementations with 32-bit integers   you don t need to add char  to the solution  unsigned int to int unsigned k        if  k    0  return 0      if  k    1  return 1                           optional        return  k   2    10   int to int k   2       HalosGhost suggested to compact the code into a single line  unsigned int int to int unsigned int k        return  k    0    k    1   k     k   2    10   int to int k   2

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You can convert decimal to bin  hexa to decimal  hexa to bin  vice-versa etc by following this example  CONVERTING DECIMAL TO BIN   int convert to bin int number       int binary   0  counter   0      while number  gt  0           int remainder   number   2          number    2          binary    pow 10  counter    remainder          counter                 Then you can print binary equivalent like this   printf  08 d   convert to bin 13      shows leading zeros

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void intToBin int digit        int b      int k   0      char  bits       bits   char    malloc sizeof char        printf  intToBin n        while  digit            b   digit   2          digit   digit   2          bits k    b          k             printf   d   b             printf   n        for  int i   k - 1  i  gt   0  i--            printf   d   bits i

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Result in string  The following function converts an integer to binary in a string  n is the number of bits       Convert an integer to binary  in a string  void int2bin unsigned integer  char  binary  int n 8        for  int i 0 i lt n i           binary i     integer  amp   int 1 lt  lt  n-i-1      1     0     binary n    0       Test online on repl it   Source   AnsWiki   Result in string with memory allocation  The following function converts an integer to binary in a string and allocate memory for the string  n is the number of bits       Convert an integer to binary  in a string  char  int2bin unsigned integer  int n 8      char  binary    char  malloc n 1     for  int i 0 i lt n i           binary i     integer  amp   int 1 lt  lt  n-i-1      1     0     binary n    0     return binary      This option allows you to write something like printf    s   int2bin 78    but be careful  memory allocated for the string must be free later   Test online on repl it   Source   AnsWiki   Result in unsigned int  The following function converts an integer to binary in another integer  8 bits maximum       Convert an integer to binary  in an unsigned  unsigned int int to int unsigned int k        return  k    0    k    1   k     k   2    10   int to int k   2         Test online on repl it  Display result  The following function displays the binary conversion     Convert an integer to binary and display the result void int2bin unsigned integer  int n 8        for  int i 0 i lt n i           putchar    integer  amp   int 1 lt  lt  n-i-1      1     0         Test online on repl it   Source   AnsWiki

User · Answer

Well  I had the same trouble     so I found this thread  I think the answer from user  pmg  does not work always   unsigned int int to int unsigned int k        return  k    0    k    1   k     k   2    10   int to int k   2         Reason  the binary representation is stored as an integer  That is quite limited  Imagine converting a decimal to binary    dec 255  - gt  hex 0xFF  - gt  bin 0b1111 1111  dec 1023 - gt  hex 0x3FF - gt  bin 0b11 1111 1111   and you have to store this binary representation as it were a decimal number   I think the solution from Andy Finkenstadt is the closest to what you need  unsigned int to int unsigned int k        char buffer 65      any number higher than sizeof unsigned int  bits per byte 8      return itoa  atoi k  buffer  2         but still this does not work for large numbers  No suprise  since you probably don t really need to convert the string back to decimal  It makes less sense  If you need a binary number usually you need for a text somewhere  so leave it in string format    simply use itoa    char buffer 65   itoa k  buffer  2

User · Answer

You could use this function to get array of bits from integer       int  num to bit int a  int  len           int arrayLen 0 i 1          while  i lt a               arrayLen                i  2                     len arrayLen          int  bits          bits  int  malloc arrayLen sizeof int            arrayLen--          while a gt 0               bits arrayLen--  a amp 1              a gt  gt  1                    return bits

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short a  short b  short c  short d  short e  short f  short g  short h  int i  char j 256    printf  BINARY CONVERTER n n n       uses  lt stdlib h gt   while 1     a 0  b 0  c 0  d 0  e 0  f 0  g 0  h 0  i 0    gets j   i atoi j   if i gt 255   printf  int i must not pass the value 255  n    i 0    if i gt  128   a 1  i i-128   if i gt  64   b 1  i i-64   if i gt  32   c 1  i i-32   if i gt  16   d 1  i i-16   if i gt  8   e 1  i i-8   if i gt  4   f 1  i i-4   if i gt  2   g 1  i i-2   if i gt  1   h 1  i i-1    printf   n d d d d d d d d n n  a b c d e f g h

[c] Converting an integer to binary in C

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