PRId64

PRId64 is a macro defined in the C standard library header inttypes.h. It expands to the correct length modifier for printing a value of type int64_t, a signed 64-bit integer, using printf-style functions. The macro is designed to provide a portable way to format 64-bit integers across different platforms and compilers.

Usage typically appears by concatenating a percent sign with the macro, for example: printf("%" PRId64 "\n", value); This approach allows the exact format specifier to be determined by the platform, so the same code prints correctly on systems where 64-bit integers have different underlying representations or format sequences.

The actual text of PRId64 varies by platform. On many Unix-like systems, int64_t corresponds to a long int, so PRId64 may expand to "ld" or "lld" depending on the environment. On Windows with MSVC, it may expand to "I64d" to be used with "%I64d". The important point is that combining "%" with PRId64 yields a portable decimal format for int64_t.

PRId64 is part of a family of macros in inttypes.h that support portable formatting for integers. Related macros include PRIu64 for unsigned decimal, PRIx64/PRIo64 for hexadecimal/octal, and their corresponding scanf equivalents such as SCNd64 and SCNu64. In C++, these macros are available via <cinttypes> and used in the same way.

In summary, PRId64 enables portable, decimal printing of 64-bit signed integers across diverse platforms.