C++ doesn’t specify whether char is signed or unsigned. Thus, the interpretation of the following declaration:

   char arr[100];

Is platform-dependent: some compilers will treat arr as an array of 100 unsigned characters whereas others will treat it as an array of 100 signed characters. The unsigned quality of char is important when dealing with raw binary data. To ensure portability, always add an explicit ‘unsigned’ specifier (or use an appropriate typedef such as UCHAR, uint8_t etc.) when you declare char variables that store binary data:

   unsigned char mp3_clip[10048576]; // 1 Mb buffer