CLOCKS_PER_SEC

 

C

Compiler support

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Strings library

Algorithms

Numerics

Date and time utilities

Input/output support

Localization support

Concurrency support (C11)

Technical Specifications

Symbol index

 

Date and time utilities

Functions

Time manipulation

difftime

time

clock

timespec_get (C11)

timespec_getres (C23)

Format conversions

asctimeasctime_s (deprecated in C23)(C11)

ctimectime_s (deprecated in C23)(C11)

strftime

wcsftime (C95)

gmtimegmtime_rgmtime_s (C23)(C11)

localtimelocaltime_rlocaltime_s (C23)(C11)

mktime

Constants

CLOCKS_PER_SEC

Types

tm

time_t

clock_t

timespec (C11)

 

Defined in header <time.h>
#define CLOCKS_PER_SEC /*implementation defined*/

Expands to an expression (not necessarily a compile-time constant) of type clock_t equal to the number of clock ticks per second, as returned by clock().

Notes

POSIX defines CLOCKS_PER_SEC as one million, regardless of the actual precision of clock.

Until standardized as CLOCKS_PER_SEC in C89, this macro was sometimes known by its IEEE std 1003.1-1988 name CLK_TCK: that name was not included in C89 and was removed from POSIX itself in 1996 over ambiguity with _SC_CLK_TCK, which gives number of clocks per second for the function times()).

References

• C23 standard (ISO/IEC 9899:2024):

• 7.27.1/2 Components of time (p: TBD)

• C17 standard (ISO/IEC 9899:2018):

• 7.27.1/2 Components of time (p: 284)

• C11 standard (ISO/IEC 9899:2011):

• 7.27.1/2 Components of time (p: 388)

• C99 standard (ISO/IEC 9899:1999):

• 7.23.1/2 Components of time (p: 338)

• C89/C90 standard (ISO/IEC 9899:1990):

• 4.12.1 Components of time

See also

clock	returns raw processor clock time since the program is started (function)
clock_t	processor time since era type (typedef)
C++ documentation for CLOCKS_PER_SEC