Thread: char array output confusion

Hello all, I'm pretty new to C, so this might be a silly question. Im doing some bitshifting in chunks of 8 bytes and outputting 7 bytes. For the output im using a char array of size 7 storing a single byte in each location. Here's where things deviate from what I expect: when I print the values at all 7 locations of my char array in hex, I get 32 bit results form each array index (which should only be ably to hold 8 bits). Why is this? Heres my relevant (and probably poorly formatted) code:
Edit: buff[] is a char array as well, declared earlier in the code. The values it outputs are correct.

Code:

                char out[7];    
          
                out[0] = ((buff[i] & 0x7f) << 1) | ((buff[i+1] & 0x40) >> 6);
                printf("%x -> %x\n",buff[i],out[0]);
                
                out[1] = ((buff[i+1] & 0x3f) << 2) | ((buff[i+2] & 0x60) >> 5);
                printf("%x -> %x\n",buff[i+1],out[1]);


                
                out[2] = ((buff[i+2] & 0x1f) << 3) | ((buff[i+3] & 0x70) >> 4);
                printf("%x -> %x\n",buff[i+2],out[2]);


                
                out[3] = ((buff[i+3] & 0x0f) << 4) | ((buff[i+4] & 0x78) >> 3);
                printf("%x -> %x\n",buff[i+3],out[3]);
    
                
                out[4] = ((buff[i+4] & 0x07) << 5) | ((buff[i+5] & 0x7c) >> 2);
                printf("%x -> %x\n",buff[i+4],out[4]);


                
                out[5] = ((buff[i+5] & 0x03) << 6) | ((buff[i+6] & 0x7e) >> 1);
                printf("%x -> %x\n",buff[i+5],out[5]);
                
                
                out[6] = ((buff[i+6] & 0x01) << 7) | (buff[i+7] & 0x7f);
                printf("%x -> %x\n",buff[i+6],out[6]);

Heres some sample output
hex on right is orig val from buff[] index hex on left is val of out[] index:
61 -> ffffffc362 -> ffffff8b
63 -> 1e
64 -> 4c
65 -> ffffffb9
66 -> ffffffb3
67 -> ffffffe8
Why are the values on the right hand side 32 bits when each one should only represent a char (1 byte) and both are printed using hex %x?

This happens probably because a negative char( if the type is signed ) gets converted to its long 32-bit form. For example:

Code:

8-bit -1  : 0xFF
32-bit -1 : 0xFFFFFFFF

If you use "unsigned char" instead, the problem will likely disappear.

EDIT: Good, you figured it out by yourself. Yes, please leave this post as it is for others to learn from your mistake.