The C99 and C11 standards specify the following length modifiers for printf(); their meanings are:
Modifier | Modifies | Applies to |
|–––––|———————|—————————————————————| | hh | d, i, o, u, x, or X | char, signed char or unsigned char | h | d, i, o, u, x, or X | short int or unsigned short int | l | d, i, o, u, x, or X | long int or unsigned long int | l | a, A, e, E, f, F, g, or G | double (for compatibility with scanf(); undefined in C90) | ll | d, i, o, u, x, or X | long long int or unsigned long long int | j | d, i, o, u, x, or X | intmax_t or uintmax_t | z | d, i, o, u, x, or X | size_t or the corresponding signed type (ssize_t in POSIX) | t | d, i, o, u, x, or X | ptrdiff_t or the corresponding unsigned integer type | L | a, A, e, E, f, F, g, or G | long double
If a length modifier appears with any conversion specifier other than as specified above, the behavior is undefined.
Microsoft specifies some different length modifiers, and explicitly does not support hh, j, z, or t.
Modifier | Modifies | Applies to |
|–––––|———————|—————————————————————| | I32 | d, i, o, x, or X | __int32 | I32 | o, u, x, or X | unsigned __int32 | I64 | d, i, o, x, or X | __int64
I64 | o, u, x, or X | unsigned __int64
I | d, i, o, x, or X | ptrdiff_t (that is, __int32 on 32-bit platforms, __int64 on 64-bit platforms)
I | o, u, x, or X | size_t (that is, unsigned __int32 on 32-bit platforms, unsigned __int64 on 64-bit platforms) l or L | a, A, e, E, f, g, or G | long double (In Visual C++, although long double is a distinct type, it has the same internal representation as double.)
l or w | c or C | Wide character with printf and wprintf functions. (An lc, lC, wc or wC type specifier is synonymous with C in printf functions and with c in wprintf functions.)
l or w | s, S, or Z | Wide-character string with printf and wprintf functions. (An ls, lS, ws or wS type specifier is synonymous with S in printf functions and with s in wprintf functions.)
Note that the C, S, and Z conversion specifiers and the I, I32, I64, and w length modifiers are Microsoft extensions. Treating l as a modifier for long double rather than double is different from the standard, though you’ll be hard-pressed to spot the difference unless long double has a different representation from double.