INTRO(3)                 DOMAIN/IX SYS5                  INTRO(3)



NAME
     intro - introduction to subroutines and libraries

USAGE
     #include <stdio.h>
     #include <math.h>


DESCRIPTION
     This section describes a variety of functions and subrou-
     tines.  Certain major categories of subroutine are identi-
     fied by a letter after the section number:

     (3C) These functions, together with those of Section 2 and
          those marked (3S), constitute the Standard C Library.
          Declarations for some of these functions may be
          obtained from #include files indicated on the appropri-
          ate pages.

     (3S) These functions constitute the "standard I/O package"
          (see stdio(3S)).  Declarations for these functions may
          be obtained from the #include file <stdio.h>.

     (3M) These functions constitute the Math Library, libm.
          Declarations for these functions may be obtained from
          the #include file <math.h>.  Several generally useful
          mathematical constants are also defined there.

     (3X) Various specialized libraries.  The files in which
          these libraries are found are given on the appropriate
          pages.

DEFINITIONS
     character      any bit pattern able to fit into a byte on
                    the machine.  The null character is a charac-
                    ter with value zero, represented in the C
                    language as \0.

     character array
                    a sequence of characters.  A null-terminated
                    character array is a sequence of characters,
                    the last of which is the null character.

     string         in C, a null-terminated character array.  The
                    null string is a character array containing
                    only the null character.  A NULL pointer is
                    the value that is obtained by casting zero
                    into a pointer.  The C language guarantees
                    that this value will not match that of any
                    legitimate pointer, so many functions that



Printed 12/4/86                                           INTRO-1

INTRO(3)                 DOMAIN/IX SYS5                  INTRO(3)



                    return pointers return zero to indicate an
                    error.  NULL is defined as zero in <stdio.h>;
                    the user can include an appropriate defini-
                    tion if not using <stdio.h>.

NOTE
     The DOMAIN System uses dynamically-loaded global libraries
     that are mapped into the machine's address space at boot
     time and, therefore, don't have to be bound with the pro-
     grams that use them.  All references to routines in global
     libraries are resolved at load time.  The routines in this
     section are in the libraries /lib/clib and /lib/unixlib.

DIAGNOSTICS
     Functions in the C and Math Libraries (Sections 3C and 3M)
     may return the conventional values 0 or +HUGE (the largest-
     magnitude single-precision floating-point numbers; HUGE is
     defined in the <math.h> header file) when the function is
     undefined for the given arguments or when the value is not
     representable.  In these cases, the external variable errno
     (see intro(2)) is set to the value EDOM or ERANGE.

WARNING
     Many of the functions in the libraries call and/or refer to
     other functions and external variables described in this
     section and in Section 2 of this volume.  If a program inad-
     vertantly defines a function or external variable with the
     same name, the presumed library version of the function or
     external variable may not be loaded.  The lint(1) program
     checker reports name conflicts of this kind as "multiple
     declarations" of the names in question.  It checks defini-
     tions for functions in sections 2, 3C, and 3S automatically.
     To check other definitions, use the -l option to lint.

RELATED INFORMATION
     intro(2), stdio(3S), ar(1), cc(1), ld(1), lint(1), nm(1)

















INTRO-2                                           Printed 12/4/86