Editing Printf (section)

===Length field===

The length field can be omitted or be any of:

{{Table alignment}}
{| class="wikitable col1center"
|-
! Text
! Description
|-
| {{tt|hh}}
| For integer types, causes {{tt|printf}} to expect an {{tt|int}}-sized integer argument which was promoted from a {{tt|char}}.
|-
| {{tt|h}}
| For integer types, causes {{tt|printf}} to expect an {{tt|int}}-sized integer argument which was promoted from a {{tt|short}}.
|-
| {{tt|l}}
| For integer types, causes {{tt|printf}} to expect a {{tt|long}}-sized integer argument.
For floating-point types, this is ignored. {{tt|float}} arguments are always promoted to {{tt|double}} when used in a [[varargs]] call.<ref name="c99io">{{cite standard| publisher= [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] | year= 1999 | title-link= C99 | title= ISO/IEC 9899:1999(E): Programming Languages – C | section= 7.19.6.1 | at= para. 7 }}</ref>
|-
| {{tt|ll}}
| For integer types, causes {{tt|printf}} to expect a {{tt|long long}}-sized integer argument.
|-
| {{tt|L}}
| For floating-point types, causes {{tt|printf}} to expect a {{tt|long double}} argument.
|-
| {{tt|z}}
| For integer types, causes {{tt|printf}} to expect a {{tt|size_t}}-sized integer argument.
|-
| {{tt|j}}
| For integer types, causes {{tt|printf}} to expect a {{tt|intmax_t}}-sized integer argument.
|-
| {{tt|t}}
| For integer types, causes {{tt|printf}} to expect a {{tt|ptrdiff_t}}-sized integer argument.
|}

Platform-specific length options came to exist prior to widespread use of the ISO C99 extensions, including:

{{Table alignment}}
{| class="wikitable col1center"
|-
! Text
! Description
! ''Commonly found platforms''
|-
| {{tt|I}}
| For signed integer types, causes {{tt|printf}} to expect {{tt|ptrdiff_t}}-sized integer argument; for unsigned integer types, causes {{tt|printf}} to expect {{tt|size_t}}-sized integer argument. || [[Win32]]/[[Win64]]
|-
| {{tt|I32}}
| For integer types, causes {{tt|printf}} to expect a 32-bit ([[double word]]) integer argument. || Win32/Win64
|-
| {{tt|I64}}
| For integer types, causes {{tt|printf}} to expect a 64-bit (quad word) integer argument. || Win32/Win64
|-
| {{tt|q}}
| For integer types, causes {{tt|printf}} to expect a 64-bit (quad word) integer argument. || [[BSD]]
|}

ISO C99 includes the <code>[[inttypes.h]]</code> header file that includes a number of [[Macro (computer science)|macros]] for platform-independent {{code|printf}} coding. For example: {{code|printf("%" PRId64, t);|c}} specifies decimal format for a [[Integer (computer science)|64-bit signed integer]]. Since the macros evaluate to a [[string literal]], and the compiler [[concatenates]] adjacent string literals, the expression {{code|"%" PRId64|c}} compiles to a single string.

Macros include:

{| class="wikitable"
|-
! Macro
! Description
|-
| {{tt|PRId32}}
| Typically equivalent to {{tt|I32d}} (''Win32/Win64'') or {{tt|d}}
|-
| {{tt|PRId64}}
| Typically equivalent to {{tt|I64d}} (''Win32/Win64''), {{tt|lld}} (''32-bit platforms'') or {{tt|ld}} (''64-bit platforms'')
|-
| {{tt|PRIi32}}
| Typically equivalent to {{tt|I32i}} (''Win32/Win64'') or {{tt|i}}
|-
| {{tt|PRIi64}}
| Typically equivalent to {{tt|I64i}} (''Win32/Win64''), {{tt|lli}} (''32-bit platforms'') or {{tt|li}} (''64-bit platforms'')
|-
| {{tt|PRIu32}}
| Typically equivalent to {{tt|I32u}} (''Win32/Win64'') or {{tt|u}}
|-
| {{tt|PRIu64}}
| Typically equivalent to {{tt|I64u}} (''Win32/Win64''), {{tt|llu}} (''32-bit platforms'') or {{tt|lu}} (''64-bit platforms'')
|-
| {{tt|PRIx32}}
| Typically equivalent to {{tt|I32x}} (''Win32/Win64'') or {{tt|x}}
|-
| {{tt|PRIx64}}
| Typically equivalent to {{tt|I64x}} (''Win32/Win64''), {{tt|llx}} (''32-bit platforms'') or {{tt|lx}} (''64-bit platforms'')
|}