[]运算符中的十六进制

我找到了一些文章,看到了:

// Capture vendor string
char vendor[0x20];
memset(vendor, 0, sizeof(vendor));
*reinterpret_cast<int*>(vendor) = data_[0][1];
*reinterpret_cast<int*>(vendor + 4) = data_[0][3];
*reinterpret_cast<int*>(vendor + 8) = data_[0][2]; 

This line: char vendor[0x20];. Why threre are hexadecimal and may I use octal value?

CPUID