Nobody substitutes random three letter strings for keywords in ordinary C code unless they intend on some trivial obfuscation.

    define O1O printf
    #define OlO putchar
    #define O10 exit
    #define Ol0 strlen
    #define QLQ fopen
    #define OlQ fgetc
    #define O1Q abs
    #define QO0 for
    typedef char lOL;