.  \"ident	"@(#)cls4:man/task/TASK.INTRO.3	1.1"
.  \"Copyright (c) 1984 AT&T
.  \"All Rights Reserved        
.  \"THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T
.  \"The copyright notice above does not evidence any           
.  \"actual or intended publication of such source code.
.TH TASK.INTRO 3C++ "C++ Task Library" " "
.SH NAME
task \- coroutines, multiple threads of control, C++ task library
.SH SYNOPSIS
\f3
.nf
#include <task.h>

class object;
class sched : public object;
class timer : public sched;
class task  : public sched;
.sp
class qhead : public object;
class qtail : public object;
.sp
class Interrupt_handler : public object;
.sp
class histogram;
class randint;
class urand : public randint;
class erand : public randint;

.fi
\f1
.sp-1.5v
.SH DESCRIPTION
The C++ task library provides facilities for writing programs
with multiple threads of control
within one UNIX system process.
Each thread of control is a \f(CWtask\fP or coroutine.
Each \f(CWtask\fP is an instance of a user-defined class derived from class
\f(CWtask\fP,
and the main program of the \f(CWtask\fP is the constructor of its class.
A \f(CWtask\fP can be suspended and resumed without interfering with its 
internal state.
Each \f(CWtask\fP runs until it explicitly gives up the processor;
there is no pre-emption.
.P
Most classes in the task system are derived from the base class
\f(CWobject\fP.
The base class
\f(CWsched\fP
is responsible for scheduling and for the functionality
that is common to \f(CWtask\fPs and \f(CWtimer\fPs.
Class \f(CWsched\fP is meant to be used strictly as a base class,
that is, it is illegal to create objects of class \f(CWsched\fP.
Class \f(CWtask\fP must also be used only as a base class.
The programmer must derive a class from class \f(CWtask\fP,
and provide a constructor to serve as the \f(CWtask\fP's main program.
The task system can be used for writing event-driven simulations.
\f(CWtask\fPs execute in a simulated time frame.
Objects of class \f(CWtimer\fP provide a facility
for implementing time-outs and other time-dependent phenomena.
Classes \f(CWtask\fP, \f(CWtimer\fP, \f(CWsched\fP, and \f(CWobject\fP
and their public member functions are described on the task(3C++)
manual page.
.P
Classes \f(CWqhead\fP and \f(CWqtail\fP
enable a wide range of message-passing and data-buffering schemes
to be implemented simply.
These classes are described on the queue(3C++) manual page.
.P
Class \f(CWInterrupt_handler\fP 
provides an interface for writing classes that can wait
for external events using UNIX system signals.
These classes are described on the interrupt(3C++) manual page.
.P
Class \f(CWhistogram\fP aids data gathering.
Classes \f(CWrandint\fP, \f(CWurand\fP, and \f(CWerand\fP
provide random number generation.
These four classes are described on the tasksim(3C++) manual page.
.SH SEE ALSO
task(3C++), queue(3C++), interrupt(3C++), tasksim(3C++)
.br
Stroustrup, B. and Shopiro, J. E.,
"A Set of C++ Classes for Co-routine Style Programming,"
in
.I "AT&T C++ Language System Release 2.0 Library Manual."
.br
Shopiro, J. E.,
"Extending the C++ Task System for Real-Time Control,"
in
.I "AT&T C++ Language System Release 2.0 Library Manual."