Appendix B - Standard Library 标准库

This appendix is a summary of the library defined by the ANSI standard. The standard library is not part of the C language proper, but an environment that supports standard C will provide the function declarations and type and macro definitions of this library. We have omitted a few functions that are of limited utility or easily synthesized from others; we have omitted multi-byte characters; and we have omitted discussion of locale issues; that is, properties that depend on local language, nationality, or culture.

The functions, types and macros of the standard library are declared in standard headers:

   <assert.h>  <float.h>   <math.h>    <stdarg.h>  <stdlib.h>
   <ctype.h>   <limits.h>  <setjmp.h>  <stddef.h>  <string.h>
   <errno.h>   <locale.h>  <signal.h>  <stdio.h>   <time.h>

A header can be accessed by

  #include <header>

Headers may be included in any order and any number of times. A header must be included outside of any external declaration or definition and before any use of anything it declares. A header need not be a source file.

External identifiers that begin with an underscore are reserved for use by the library, as are all other identifiers that begin with an underscore and an upper-case letter or another underscore.

• B.1 Input and Output: <stdio.h>

• B.2 Character Class Tests: <ctype.h>

• B.3 String Functions: <string.h>

• B.4 Mathematical Functions: <math.h>

• B.5 Utility Functions: <stdlib.h>

• B.6 Diagnostics: <assert.h>

• B.7 Variable Argument Lists: <stdarg.h>

• B.8 Non-local Jumps: <setjmp.h>

• B.9 Signals: <signal.h>

• B.10 Date and Time Functions: <time.h>

• B.11 Implementation-defined Limits: <limits.h> and <float.h>