A DEVELOPMENT OF THAI KERNEL SYSTEM
PORNPOTE SURIYAWONG
Researcher
Dept. of Computer Engineering
Kasetsart University, Thailand
YUEN POOVARAWAN
Associate Professor
Dept. of Computer Engineering
Kasetsart University, Thailand
CHAIYONG WONGCHAISUWAT
Assistant Professor
Dept. Of Computer Engineering
Kasetsart University, Thailand
SUMMARY
This paper presents the design and development of the Thai
K e r n e l S y s t e m ( T KS ) f o r a p p l i ca t i on t o T ha i d a ta p ro c e s s i ng
activities. With the layered organization, TKS consists of several
low-level service routines which can be accessed easily through
system calls. As TKS is hardware independence, it can be mounted and
applied on different computer systems. The proposed kernel written
in the C and assembly language for 16-bit microcomputer is divided
into three parts as follows:- Physical Device Driver (PDD), Logical
Device Driver (LDD) and, Function calls and Library Functions (FCLF).
With bit-image-graphic mode for Thai displaying, Thai software
packages such as wo rd-processors, graphics, spreadsheets and
databases which are accessed through the proposed TKS can be
developed successfully with less time and effort.
INTRODUCTION
Recently a microcomputer has gained significant popularity
especially as a personal use primarily due to its high performance
and flexible software package. In Thailand, the characteristics of
Thai language which are writter in 4 levels are unique and ambiguous.
There is no clear punctuation or blank between words for Thai word
separation.
To use Thai software either locally self developed as
Thai word-processors or modified from the imported packages as Lotus
1-2-3, dBASE etc, an enhanced CRT controller card and a specific
driver are needed for Thai character displaying.
With
several
incompatible
hardware
cards
designed
from
different vendors, Thai application programs are individually
developed.
They are practically unable to run across or transfer
between them.
Due to the problem of hardware independence, the
growth of Thai local software development is very difficult and
limited.
In the recent years, displaying Thai characters on bit image
graphic mode has been developed to avoid the modification of hardware.
However, with vendors’ different hardware configurations, Thai
application software are still separately developed.
Upgrading
either hardware or operating systems causes the problems of software
modification.
To avoid the problems mentioned above, in this research, the
system called “Thai Kernel System – TKS” based on the layered
organization is proposed.
The layering approach with system call
interfacing between layers have been found in most modern operating
systems i.e. UNIX [1], OS/2 [2] and in applications i.e. Graphical
Kernel System, GKS [3,4].
The system service routines of TKS for
Thai processing activities are provided to interface between the user
program and I/O systems of keyboard, printer and video displays.
Thai application programs under TKS are hardware independence and
applicable to expand and mount on higher level machines.
This paper presents the structure and applications of TKS, as
wel as the possibility of the expansion of this proposed system.
THE STRUCTURE OF TKS
Thai Kernel system (TKS) is developed to solve the problem of
incompatible that occurs in the usage of Thai language on computer.
TKS is a set of function service routines for Thai data processing.
The properties of the proposed TKS are listed below.
1. All service routines are easy to apply with specific
function numbers called from the user program.
2. Basic I/O routines dealt with Thai language such as keyboard,
printer and video functions are provided.
3. They can be easily modified and extended.
4. Only the lowest layer of TKS interacts directly with I/O
devices to handle device-specific activities. User programs
access devices by name under a layer of high level device
independent I/O operations.
Since the structure of TKS is in the lower level closed to the
hardware for Thai data processing, it is divided as layered
organization (Fig. 1) for ease of calling and applying effectively.
Fig. 1. The Structure of TKS
The lowest layer of TKS called Physical Device Driver (PDD)
consists of a set of procedures performing the real work of carrying
out the physical input and output operations and fielding interrupts.
It is kept as small as possible so it can be easily ported into many
kinds of machines. The upper layer above PDD called Logical Device
Driver (LDD) is provided in TKS to carry out the redirection and
piping of the physical devices.
Finally, the highest layer called
Function Call and Library Function (FCLF) is a collection of service
routines of high-level operations for manipulating all Thai data
processing.
The proposed TKS is mainly implemented on portable C
programming language for 16-bit microcomputer. Some portion of PDD
is also written in assembly language for gaining the most
effectiveness in speed and manipulating the hardware easily. For the
near future, this proposed TKS will be upgraded and mounted on
different operating systems and hardware configurations.
PHYSICAL DEVICE DRIVER
In TKS, the Physical Device Driver (PDD) manages input from the
keyboard and output to the display screen and the printer. Since the
PDD interacts directly with the hardware, the modification or
reinstallation of hardware configurations causes this layer to be
changed.
Procedures in higher layers call routines in PDD through
system calls with well-defined entry of a specific device number.
Only video display, keyboard and printer have been installed in this
current version of TKS.
The video display installed in TKS shows characters on screen
in virtual text mode for bit image graphics display. Twenty dots or
scan lines will be used to display Thai language in 4 levels
structure as shown in Fig. 2. The scan lines for tone marks, upper
vowels, normal vowels and consonants, and lower vowels are proposed
as 4, 4, 8 and 4 lines respectively. All characters width is assumed
to be 8 dots equally. With the defined character size, the number of
lines and columns for the different resolutions of video systems are
carried out in Table 1.
Fig. 2. Thai language structure for video displaying
Table 1.
Video Systems
CGA
MGA
EGA
MCGA
VGA
Video Display System
Resolution
640x200
720x348
640x350
640x480
640x480
No. of Lines
10
17
17
24
24
No. of Columns
80
90
80
80
80
The input from keyboard is normally in ASCII codes. To receive
Thai character in TISI code [5], the PDD of TKS will map the English
ASCII code into Thai TISI code with table look-up approach.
The
appropriate table from two standard Thai keyboard types namely
Pattachote and Gatmanee is selected prior to the table look-up
mapping. The routine for keyboard inputting process is shown in Fig.
3.
RECEIVE DATA FROM KEYBOARD
IF THAI-KEYBOARD THEN
IF PATTACHOTE THEN
LOOK-UP IN PATTACHOTE TABLE
ELSE
LOOK-UP IN GATEMANEE TABLE
ENDIF
ENDIF
RETURN DATA
Fig. 3.
Keyboard inputting algorithm
The printer outputting concerns the status checking and the
transferring of ASCII data in either English or Thai code to printer.
The formats of PDD system call functions for video display, keyboard
and printer are in the same form as follows:vdo_func(<function no.> [argument [,…]])
kbd_func(<function no.> [argument [,…]])
and_prn_func(<function no.> [argument [,…]])
where <function no.> is the specific number for each device functions.
LOGICAL DEVICE DRIVER
In TKS, the Logical Device Driver (LDD) manage input from and
output to standard devices already defined in Table 2. The purpose
of this layer is inserted in the system for the redirection and
piping of physical devices as shown in Fig. 4 and 5.
Table 2.
Logical
Device Name
Stdin
Stdout
Stderr
Stdaux
Stdprn
Standard Logical Devices
Meaning
Standard
Standard
Standard
Standard
Standard
Input
Output
Error Display
Auxiliary
Printing
Physical Devices
Keyboard
Video Display
Video Display
Communication Device
Printer
Fig. 5.
Piping
There may be two methods to redirect the standard devices for
processing data either via operating systems or directly on devices.
The method via operating systems is chosen in TKS due to its easiness
in implementation. It functions as a filter to operating systems as
shown in Fig. 6.
Fig. 6.
Method of Redirection in TKS
The format of LDD system call functions for standard device is
Ldd_func( <function no.>, <logical device>, [argument,…] )
where <function no.> refers to a specific device routine which is
already defined in the PDD layer.
LIBRARY FUNCTION AND APPLICATION
Function Call and Library Function (FCLF) is a collection of
procedures (functions) available for Thai data processing and other
complex frequently used routines.
The procedures putting in the
library are more complex than the lower layers of LDD and PDD. They
are two groups of procedures namely I/O system and Thai system.
I/O system procedures are provided as abstract operations for
user programs. They can be called or accessed by either a function
number or a library function through the lower layer of physical
devices. Thai system procedures are provided to manipulate all Thai
data processing activities such as Thai searching, sorting and Thai
language leveling etc. in the form of library functions.
The proposed TKS has been used extensively as the system call
interfacing
for
Thai
microcomputer
software
packages
under
development at Kasetsart University.
Those software packages are
Thai word-processor, Thai spreadsheet, Thai database management
system and Thai graphics software. It is shown that the development
of application program accessed through this proposed TKS can be
easily implemented with less time and effort.
With the extended
version of TKS that will be developed in the future, the application
programs on 16-bit microcomputer now can be portable to higher-level
machines with different operating systems.
DISCUSSION AND CONCLUSION
The Thai Kernel System TKS proposed in this research is the
basic primitive operations as a system call services to work along
with Thai Application programs. Under the environment of TKS, user
programs can be run on several hardware configurations without any
modification.
The layered organization of the TKS is divided into three parts.
The lower layer of physical device driver interacts directly with the
I/O hardware.
The next upper layer is logical device driver for
redirection and piping the standard devices.
The upper layer is a
collection of I/O system procedures as function calls and Thai system
procedures as library function.
The current version of TKS is developed for 16 bit
microcomputer under MS-DOS environment.
The next move will be the
implementation of proposed TKS on upper level machine of an
engineering workstation. Under UNIX-based system.
REFERENCE
1.
M.J. Bach (1986), The Design of the UNIX
Prentice-Hall, Englewood Cliffs, New Jersey.
2.
E. Lacobucci
California.
3.
American National Standards Institute, Inc. (1985), Computer
Graphics – Graphical Kernel (GKS) Gunctional Description, ANSI
X3, 124, New York.
4.
F.R.A. Hopgood, D.A. Duce, J.R. Gallop and D.C. Sutcliffe
(1986), Introduction to the Graphical Kernel System (GKS), 2nd
Edn, Academic Press Inc., London.
5.
Thai Industrial Standard Institute (1986), TISI 620-1986 Thai
Character Code for Computer, Bangkok, Thailand.
(1988),
OS/2
Programmer’s
Operating
Guide,
System,
McGraw-Hill,