|Input the hexadecimal value||The binary result is|
Hex to binary is probably the easiest conversion between the number systems. To turn a hexadecimal value to a binary number do the following
Here is a table that contains the hex-to-binary mappings:
Download the source code of the example implementation from here: hex-to-bin.zip
The hex to binary algorithm doesn't have any fancy tricks. It is straight forward work with strings.
We begin by reading a hex number, up to 100 digits long. Of course we reserve one byte for the null terminating symbol. That's why the size of the array hex is 101 elements. After we read the input we begin the conversion in the hexToBinary function.
The binary char pointer holds the result. Now, looking at the table above you see that for each hex digit we need exactly 4 binary digits. Plus we want to insert spaces between the digits, so the result is easier to read. That's why, we allocate 5 times the length of the input + 1 element for the terminating symbol.
Then we loop through the hex value and take the corresponding binary string with a switch. The inner while just copies the current binary number into the pointer that holds the final result.
Finally, we reset the binary pointer, so that it points to the beginning of the bin value.
That's it, really simple – just handling strings.
length = strlen(hex);
binary = hexToBinary(hex, length);
printf("%s in hexadecimal is %sin binary\n", hex, binary);
char *binary = (char*) malloc(length * 5 + 1);
if(binary == NULL)
while(*hex != '\0')
char *binaryValue = valueOf(*hex);
while(*binaryValue != '\0')
*binary++ = *binaryValue++;
*binary = '\0';
binary -= length * 5;
See also how to convert from: