How to Print Unsigned Chars as Hexadecimal in C Using ostream?

Printing Unsigned Chars as Hexadecimal in C Using ostream

In C , printing unsigned 8-bit variables directly using ostream treats them as characters, resulting in inaccurate hexadecimal representation. To overcome this, there are several methods available:

Casting to int

One common approach is to cast the unsigned char to an integer before printing. This forces ostream to treat the value as a hexadecimal number. For example:

cout << "a is " << hex << (int) a << "; b is " << hex << (int) b << endl;

Using hex manipulator with int

Alternatively, you can use the hex stream manipulator directly with an integer. This will convert the integer to hexadecimal representation and append it to the stream. For example:

cout << "a is " << hex << int(a) << "; b is " << hex << int(b) << endl;

Using hex manipulator with setw and setfill

If you require leading zeros for padding, you can combine the hex manipulator with setw and setfill to specify the desired width and fill character. For example:

#include <iomanip>
...
cout << "a is " << setw(2) << setfill('0') << hex << int(a);

Creating a macro

You can simplify the printing process by creating a macro that combines the necessary манипуляции. For example:

#define HEX( x )
   setw(2) << setfill('0') << hex << (int)( x )

With this macro, you can simply write:

cout << "a is " << HEX( a );

MartinStettner's solution

Another elegant solution is to create a custom stream inserter for unsigned chars that automatically prints them as hex. Please refer to the original question and answer for more details on MartinStettner's approach.

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