How do I print unsigned char values as hexadecimal in C using ostream?

Printing Unsigned Char as Hex Using Ostream in C

In C , handling unsigned 8-bit variables can be done using either unsigned char or uint8_t. However, printing these variables directly using ostream interprets them as characters, leading to undesired results as observed when dealing with unsigned integer values.

To accurately display unsigned char or uint8_t as hexadecimal values, you need to cast them to int before passing them to ostream. For example, instead of:

cout << "a is " << hex << a << "; b is " << hex << b << endl;

Use:

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

This approach ensures that the data is treated as an integer, resulting in the correct hexadecimal representation.

If you want to add padding with leading zeros, you can include the header file and use the following syntax:

cout << "a is " << setw(2) << setfill('0') << hex << (int) a;

Furthermore, to simplify this process, you can create a macro:

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

This allows you to print hex values concisely using:

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

However, it's worth considering an alternative approach suggested by MartinStettner, which involves using the manipulator std::hex, making the code more readable and eliminating the need for casting:

cout << "a is " << std::hex << a << "; b is " << std::hex << b << endl;

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