I am confused about QByteArray data. Can someone please explain the below scenario for me.

Here data type for each array index is char. I understand some of those values. Like 74 'J'
I understand the first one is ASCII and second one is the corresponding character. But what is the meaning of -1 '\\377'
Also what does the below gui means?? I sent the QByteArray of above to a function which takes the QByteArray as unsigned char* source. The below gui is showing the value of that source.

The main confusing part is the first line’s value 0x87089e8 "\377\330\377\340"
charin C/C++ is a signed 1-byte integer. This GUI is simply expressing that value as a signed decimal number, and the equivalent ASCII character.You’re asking about the byte value -1, which can be interpretted in the following ways:
Note that there isn’t a standard printable ASCII character for 255, which is why they show it like they do.
Another Example: