Decimal to Binary

by

Here’s an elegant solution:

void getBin(int num, char *str)
{
  *(str+5) = '\0';
  int mask = 0x10 << 1;
  while(mask >>= 1)
    *str++ = !!(mask & num) + '0';
}

Here, we start by making sure the string ends in a null character. Then, we create a mask with a single one in it (its the mask you would expect, shifted to the left once to account for the shift in the first run of the while conditional). Each time through the loop, the mask is shifted one place to the right, and then the corresponding character is set to either a ‘1’ or a ‘0’ (the !! ensure that we are adding either a 0 or a 1 to '0'). Finally, when the 1 in the mask is shifted out of the number, the while loop ends.

To test it, use the following:

int main()
{
  char str[6];
  getBin(10, str);
  printf("%s\n", str);
  return 0;
}

More Related Contents:

  1. Are the shift operators () arithmetic or logical in C?
  2. What is Bit Masking?
  3. Casting float to int (bitwise) in C
  4. What does the statement if (counter & (1
  5. Encoding int value as an IEEE-754 float (binary32)
  6. C reverse bits in unsigned integer
  7. What is bit masking?
  8. decimal of numbers in c
  9. How do I store a 16 byte binary value that can be represented as a 32 hexadecimal characters in an unsigned char* variable in C
  10. C: Reading strings from binary file
  11. Are the results of bitwise operations on signed integers defined?
  12. Fast computing of log2 for 64-bit integers
  13. Operator precedence (bitwise ‘&’ lower than ‘==’)
  14. Bitfield manipulation in C
  15. Fastest way to clamp a real (fixed/floating point) value?
  16. How to extract the decimal part from a floating point number in C?
  17. C++ – Decimal to binary converting
  18. What does -fwrapv do?
  19. set the m-bit to n-bit [closed]
  20. Bitshift and integer promotion?
  21. Efficient bitwise operations for counting bits or find the right|left most ones
  22. How to define and work with an array of bits in C?
  23. Implementing Logical Right Shift in C
  24. Algorithm to generate bit mask
  25. Performance wise, how fast are Bitwise Operators vs. Normal Modulus?
  26. Check if a number is non zero using bitwise operators in C
  27. How to get position of right most set bit in C
  28. Can you control what a bitwise right shift will fill in C?
  29. Bitwise shifting array of char’s
  30. How to implement Bitcount using only Bitwise operators?

Leave a Comment