intro.3

unix v7是最后一个广泛发布的研究型UNIX版本

.TH INTRO 3
.SH NAME
intro \- introduction to library functions
.SH SYNOPSIS
.B #include <stdio.h>
.PP
.B #include <math.h>
.SH DESCRIPTION
This section describes functions that may be found
in various libraries, other than those functions
that directly invoke UNIX system primitives,
which are described in section 2.
Functions are divided into various libraries distinguished
by the section number at the top of the page:
.TP 6n
(3)
These functions, together with those of section 2 and those
marked (3S), constitute library
.I libc,
which is automatically loaded by the C compiler
.IR cc (1)
and the Fortran compiler
.IR f77 (1).
The link editor
.IR ld (1)
searches this library under the `\-lc' option.
Declarations for some of these functions may be obtained
from include files indicated on the appropriate pages.
.TP
(3M)
These functions constitute the math library,
.I libm.
They are automatically loaded as needed by the Fortran compiler
.IR f77 (1).
The link editor searches this library under the `\-lm' option.
Declarations for these functions may be obtained from
the include file <math.h>.
.TP 
(3S)
These functions constitute the
`standard I/O package',
see
.IR stdio (3).
These functions are in the library
.I libc
already mentioned.
Declarations for these functions may be obtained from
the include file <stdio.h>.
.TP
(3X)
Various
specialized libraries have not been given distinctive
captions.
The files in which these libraries are found are named
on the appropriate pages.
.SH FILES
/lib/libc.a
.br
/lib/libm.a, /usr/lib/libm.a (one or the other)
.SH SEE ALSO
stdio(3),
nm(1), ld(1), cc(1), f77(1), intro(2)
.SH DIAGNOSTICS
Functions in the math library (3M) may return
conventional values when the function is undefined for the
given arguments or when the value is not representable.
In these cases the external variable
.I errno
(see
.IR intro (2))
is set to the value EDOM
or ERANGE.
The values of EDOM and ERANGE are defined in
the include file
.I <math.h>.
.SH ASSEMBLER
In assembly language these functions may be accessed
by simulating the C calling sequence.
For example,
.IR ecvt (3)
might be called this way:
.IP ""
.globl	_ecvt
.nf
setd
mov	$sign,\-(sp)
mov	$decpt,\-(sp)
mov	ndigit,\-(sp)
movf	value,\-(sp)
jsr	pc,_ecvt
add	$14.,sp
.fi