| An Overview of the SAS/C Debugger |
This chapter introduces the methods of running the SAS/C
Debugger, summarizes its capabilities, and provides a quick start to using
the debugger under the CMS and OS/390 operating environments.
The SAS/C Debugger
helps you find run-time errors, or bugs, in programs that have been compiled
by the SAS/C Compiler. This process
is commonly referred to as debugging. The debugger has been designed to help
you determine the location of errors in your programs and the reasons why
the errors are occurring.
There are two interactive methods of running the SAS/C Debugger
under both CMS and OS/390: full-screen mode and line mode. If you are running
under OS/390, you can also run the debugger noninteractively in batch mode.
In
full-screen mode, the SAS/C Debugger
must be used with an IBM 3270 type of terminal display system or an emulator.
Today, most people work on a Windows operating environment that uses 3270
emulator software. If your terminal supports full-screen applications, the
SAS/C Debugger runs in full-screen
mode by default. In full-screen mode, the debugger provides an interactive
windowing interface that enables you to view information and operate through
a series of windows. Each window has a distinct function and displays logically
related data. You will probably find that full-screen mode offers the most
efficient interface.
You
can override the default and run the debugger interactively in line mode.
In line mode, you issue debugger commands at the Cdebug:
prompt, and the screen displays information in response. The SAS/C Debugger
supports all commands from previous releases as well as several new features
for Release 7.00. You can switch to line mode after invoking the debugger,
as described in Switching to Line Mode.
The
OS/390 data set can be routed to any system output device that is available
at your site, including a direct access storage device or your terminal. The
details of batch mode are presented in Running the Debugger under TSO and in
Running the Debugger under OS/390 Batch.
Regardless of the
method you use to run the debugger, you will find that it has many capabilities
that will enhance your productivity. With the SAS/C
Debugger, you can
The SAS/C
Debugger must be used with an IBM 3270 type of terminal display system or
emulator. An IBM mainframe environment handles screen display differently
from a UNIX or Windows environment. If you are new to IBM mainframes, be
aware of some of the differences, because they affect the way you interact
with the SAS/C Debugger. A basic understanding
of 3270 concepts helps you to understand why the debugger reacts in a manner
that may seem unfamiliar to you. These differences are explained in the following
section.
Typically, under the UNIX or Windows environments, input
characters are available to an application program immediately as they are
typed. In fact, the terminal may be equipped with keys that allow characters
to be deleted from or inserted into a string of characters that is input to
an application program. The application program processes all characters as
they are input until a complete field is assembled.
Instead of single-character, unbuffered input and output
as is used under the Windows or UNIX environments, the IBM 3270 terminal environment
maps each character on the display to a storage area in the device. This storage
area is known as the character buffer. The applications program, in this case
the SAS/C Debugger, uses commands
to send or receive data from this buffer. The data that is transferred between
a terminal and an application is referred to as the data stream. An IBM 3270
data stream includes commands and control characters that specify the processing
of the data in the character buffer. Most often, the buffered data are grouped
into fields and formatted by using display attribute codes.
An application program can then display information
by constructing a data stream and sending it to the device. Input is obtained
by reading the buffered data and decoding the data stream that is returned.
As a result, in IBM data stream programming, output to the terminal is the
result of a command; input to an application program occurs only when the
ENTER key or a program function key is pressed.
Once a data stream is constructed, an application program
in an IBM mainframe environment must ask the operating environment to transmit
it to the terminal.
Note:
The ability to display attributes
such as color or reverse video may be limited by the capabilities of your
terminal. ![[cautionend]](../common/images/cautend.gif)
Differences in Handling Characters summarizes some important differences between the IBM 3270 full-screen communication
and other environments. Be aware of these differences when you use the SAS/C Debugger.
For additional information about the IBM 3270 data stream and full-screen
programming, see the SAS/C Full-Screen
Support Library User's Guide.
Copyright © 2001
by SAS Institute Inc., Cary, NC, USA. All rights reserved.
