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MISC.TXT
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@Uncategorized/Miscellaneous Topics
:help:?
^HelpPC Programmers Reference
^Please register this product by sending $25 (US) to:
David Jurgens
1550 Alton Darby Creek Road
Columbus, OH 43228
CompuServe 71270,2422
^Keys used for navigating through HelpPC
Esc Exit current screen or HelpPC
End Moves text or menu to the last line/item
Home Moves text or menu to the first line/item
PgUp Moves text or menu to page top or previous page
PgDn Moves text or menu to page bottom or next page
F1 Switches from menu to prompting mode and vice versa
Alt-P Write current topic to printer
Alt-W Write topic to file HelpPC.DAT in the current directory
Alt-X Exit HelpPC and without clearing current screen
^Using HelpPC
HelpPC has two modes of operation. The first is the Prompted Mode
where you specify the topic on the command line and HelpPC prompts
you for topics until you exit. The second is the Menu Mode which
as its name implies is menu driven. To use the Menu Mode just omit
the topic from the command line. You may switch between Menu mode
and Prompted Mode with the F1 key.
^Examples of Command Line
% For information about: Use the following:
Installation: HelpPC install
Creating help files: HelpPC helppc format
Interrupts: HelpPC int #
example: HelpPC int 13
Interrupt subfunction: HelpPC int #,func
example: HelpPC int 21,4E
C function usage: HelpPC function
examples: HelpPC open
HelpPC is...
HelpPC str...
Other topics: HelpPC interrupt table
examples: HelpPC bios data area or HelpPC bda
HelpPC ansi codes
All topics are treated as lower case
^Trademarks of Vendors Mentioned in HelpPC Databases
∙ PC/AT, PC-DOS, PC/XT and PS/2 are trademarks of International
Business Machines Corporation
∙ Compaq is a registered trademark of Compaq Computer Corporation
∙ CompuServe is a registered trademark of CompuServe Incorporated
∙ DESQview is a trademark of Quarterdeck Office Systems
∙ Epson is a registered trademark of Seiko Epson Corporation
∙ HP is a registered trademark of Hewlett-Packard Company
∙ IBM is a registered trademark of International Business Machines Corp.
∙ Intel is a registered trademark of Intel Corporation
∙ LIM and EMS are trademarks of Lotus, Intel and Microsoft Corporations
∙ Maxtor is a trademark of Maxtor Corporation
∙ Microsoft is a registered trademark of Microsoft Corporation
∙ NEC is a registered trademark of NEC Electronics Incorported
∙ Tandy is a registered trademark of Tandy Corporation
∙ Turbo C is a registered trademark of Borland International Inc.
∙ Other brand and product names are trademarks or registered
trademarks of their respective holders.
- see INSTALL HELPPC FORMAT
:install:setup
^INSTALL/SETUP - HELPPC Installation
Installation requires two steps. First, simply uncompress the
HelpPC archive file. Second, issue the following command:
SET HLP=d:dirname (no blanks, except between "SET HLP")
Where 'd:' is the drive and 'dirname' is the directory where the
HelpPC.NDX and the .TXT files will reside (should be fully qualified,
with or without the trailing backslash '\', see example below).
HelpPC.COM can exist anywhere it can be accessed through the DOS
command search path (PATH). The "SET HLP=" command should be placed
in the AUTOEXEC.BAT file to allow easy access to the database each
time your PC is rebooted. It is recommended that HelpPC.COM be
renamed to something quick and comfortable to use, like H.COM or
HELP.COM.
As an example, if the files HelpPC.NDX and the .TXT files reside in
a directory named C:\HELPINFO then use:
%SET HLP=C:\HELPINFO or SET HLP=C:\HELPINFO\
:helppc format
^HelpPC Text File Format
HelpPC in its standard form can handle 2000 indexed topics and
16 independent help files. If you find you need a larger capacity,
please contact me at one of the addresses below. Each file must
have its own title which will show up in the main menu. Each topic
following the file title (see below) will show up in the subtopic
menu. Also note that HelpPC will adjust the menu format based on
the screen height and the number of items in the main menu.
HelpPC text files are simple ASCII files that contain control codes
in column one. Each file must contain a title in the first line.
The remainder of the file consists of keyed lines and help text.
Each line must end with a CR/LF pair (standard DOS format) and
shouldn't be longer than 70 characters. Tabs are treated as
physical data and are not handled logically. The following is a
list of keys:
'@' in column 1 indicates a file title which will appear in
the main topic menu. This must be the very first line
in the file and has a maximum length of 40 characters
(excluding the '@').
':' in column 1 indicates a subtopic key. Multiple keys separated
by colons ':' can be entered on the same line.
'#' in column 1 indicates a highlighted title line (not centered)
'^' in column 1 indicates a centered highlighted title
'<' text that should not be shifted right
' ' in column 1 indicates a text line. Text lines are shift
right 7 characters when displayed.
any other character in column 1 is invalid
Use the BUILD command to index/reindex the default help text files.
To add your own files to the index use the command:
% BUILD [fname [file2 ...]]
%Limits of the HelpPC program
Max items in main topic menu: 16
Max items in subtopic menu: 512
Max topics in index: 2000
Max size of topic text: 16384 bytes
Max lines of text per topic: 512
Max topic key length: 20
Max file title length: 40
No limit on file size
%Example help file:
@This title appears in main menu
:key1:key2:key3
^This line will show up centered and highlighted
%This line will show up highlighted
These lines are normal text. All three topic keys will point to
this same database entry.
:character codes:character set:ascii:ebcdic:extended ascii
^ASCII - EBCDIC - Character Codes and Character Sets
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
0 000 00 NUL NUL
1 001 01 SOH SOH
2 002 02 STX STX
3 003 03 ETX ETX
4 004 04 PF EOT
5 005 05 HT ENQ
6 006 06 LC ACK
7 007 07 DEL BEL
8 010 08 ... BS
9 011 09 ... HT
10 012 0A ... SMM LF
11 013 0B VT VT
12 014 0C FF FF
13 015 0D ... CR CR
14 016 0E SO SO
15 017 0F SI SI
16 020 10 DLE DLE
17 021 11 DC1 DC1
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
18 022 12 DC2 DC2
19 023 13 TM DC3
20 024 14 RES DC4
21 025 15 NL NAK
22 026 16 BS SYN
23 027 17 IL ETB
24 030 18 CAN CAN
25 031 19 EM EM
26 032 1A ... CC SUB
27 033 1B CU1 ESC
28 034 1C IFS FS
29 035 1D IGS GS
30 036 1E IRS RS
31 037 1F IUS US
32 040 20 DS SP
33 041 21 ! SOS !
34 042 22 " FS "
35 043 23 # #
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
36 044 24 $ BYP $
37 045 25 % LF %
38 046 26 & ETB &
39 047 27 ' ESC '
40 050 28 ( (
41 051 29 ) )
42 052 2A * SM *
43 053 2B + CU2 +
44 054 2C , ,
45 055 2D - ENQ -
46 056 2E . ACK .
47 057 2F / BEL /
48 060 30 0 0
49 061 31 1 1
50 062 32 2 SYN 2
51 063 33 3 3
52 064 34 4 PN 4
53 065 35 5 RS 5
54 066 36 6 UC 6
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
55 067 37 7 EOT 7
56 070 38 8 8
57 071 39 9 9
58 072 3A : :
59 073 3B ; CU3 ;
60 074 3C < DC4 <
61 075 3D = NAK =
62 076 3E > >
63 077 3F ? SUB ?
64 100 40 @ SP @
65 101 41 A A
66 102 42 B B
67 103 43 C C
68 104 44 D D
69 105 45 E E
70 106 46 F F
71 107 47 G G
72 110 48 H H
73 111 49 I I
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
74 112 4A J ¢ J
75 113 4B K . K
76 114 4C L < L
77 115 4D M { M
78 116 4E N + N
79 117 4F O | O
80 120 50 P & P
81 121 51 Q Q
82 122 52 R R
83 123 53 S S
84 124 54 T T
85 125 55 U U
86 126 56 V V
87 127 57 W W
88 130 58 X X
89 131 59 Y Y
90 132 5A Z ! Z
91 133 5B [ $ [
92 134 5C \ * \
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
93 135 5D ] ) ]
94 136 5E ^ ; ^
95 137 5F _ ¬ _
96 140 60 ` `
97 141 61 a / a
98 142 62 b b
99 143 63 c c
100 144 64 d d
101 145 65 e e
102 146 66 f f
103 147 67 g g
104 150 68 h h
105 151 69 i i
106 152 6A j j
107 153 6B k , k
108 154 6C l % l
109 155 6D m _ m
110 156 6E n > n
111 157 6F o ? o
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
112 160 70 p p
113 161 71 q q
114 162 72 r r
115 163 73 s s
116 164 74 t t
117 165 75 u u
118 166 76 v v
119 167 77 w w
120 170 78 x x
121 171 79 y y
122 172 7A z : z
123 173 7B { # {
124 174 7C | @ |
125 175 7D } ' }
126 176 7E ~ = ~
127 177 7F "
128 200 80 Ç
129 201 81 ü a
130 202 82 é b
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
131 203 83 â c
132 204 84 ä d
133 205 85 à e
134 206 86 å f
135 207 87 ç g
136 210 88 ê h
137 211 89 ë i
138 212 8A è
139 213 8B ï
140 214 8C î
141 215 8D ì
142 216 8E Ä
143 217 8F Å
144 220 90 É
145 221 91 æ j
146 222 92 Æ k
147 223 93 ô l
148 224 94 ö m
149 225 95 ò n
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
150 226 96 û o
151 227 97 ù p
152 230 98 ÿ q
153 231 99 Ö r
154 232 9A Ü
155 233 9B ¢
156 234 9C £
157 235 9D ¥
158 236 9E ₧
159 237 9F ƒ
160 240 A0 á
161 241 A1 í
162 242 A2 ó s
163 243 A3 ú t
164 244 A4 ñ u
165 245 A5 Ñ v
166 246 A6 ª w
167 247 A7 º x
168 250 A8 ¿ y
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
169 251 A9 ⌐ z
170 252 AA ¬
171 253 AB ½
172 254 AC ¼
173 255 AD ¡
174 256 AE «
175 257 AF »
176 260 B0 ░
177 261 B1 ▒
178 262 B2 ▓
179 263 B3 │
180 264 B4 ┤
181 265 B5 ╡
182 266 B6 ╢
183 267 B7 ╖
184 270 B8 ╕
185 271 B9 ╣
186 272 BA ║
187 273 BB ╗
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
188 274 BC ╝
189 275 BD ╜
190 276 BE ╛
191 277 BF ┐
192 300 C0 └
193 301 C1 ┴ A
194 302 C2 ┬ B
195 303 C3 ├ C
196 304 C4 ─ D
197 305 C5 ┼ E
198 306 C6 ╞ F
199 307 C7 ╟ G
200 310 C8 ╚ H
201 311 C9 ╔ I
202 312 CA ╩
203 313 CB ╦
204 314 CC ╠
205 315 CD ═
206 316 CE ╬
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
207 317 CF ╧
208 320 D0 ╨
209 321 D1 ╤ J
210 322 D2 ╥ K
211 323 D3 ╙ L
212 324 D4 ╘ M
213 325 D5 ╒ N
214 326 D6 ╓ O
215 327 D7 ╫ P
216 330 D8 ╪ Q
217 331 D9 ┘ R
218 332 DA ┌
219 333 DB █
220 334 DC ▄
221 335 DD ▌
222 336 DE ▐
223 337 DF ▀
224 340 E0 α
225 341 E1 ß
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
226 342 E2 Γ S
227 343 E3 π T
228 344 E4 Σ U
229 345 E5 σ V
230 346 E6 µ W
231 347 E7 τ X
232 350 E8 Φ Y
233 351 E9 Θ Z
234 352 EA Ω
235 353 EB δ
236 354 EC ∞
237 355 ED φ
238 356 EE ε
239 357 EF ∩
240 360 F0 ≡ 0
241 361 F1 ± 1
242 362 F2 ≥ 2
243 363 F3 ≤ 3
244 364 F4 ⌠ 4
% Extended
% Dec Octal Hex ASCII EBCDIC ASCII
245 365 F5 ⌡ 5
246 366 F6 ÷ 6
247 367 F7 ≈ 7
248 370 F8 ° 8
249 371 F9 ∙ 9
250 372 FA ·
251 373 FB √
252 374 FC ⁿ
253 375 FD ²
254 376 FE ■
255 377 FF
:ansi codes:ansi control codes
^ANSI.SYS and NANSI.SYS Functions - ANSI x3.64
ESC[y,xH Cursor position y,x
ESC[nA Cursor Up n lines
ESC[nB Cursor Down n lines
ESC[nC Cursor Forward n characters
ESC[nD Cursor Backward n characters
ESC[y;xf Cursor position y,x (less frequently used)
ESC[y;xR Cursor position report y,x
ESC[6n Device status report (cursor pos)(n is constant 'n')
ESC[s Save cursor position
ESC[u Restore cursor position
ESC[2J Erase display
ESC[K Erase to end of line
ESC[nL Inserts n blank lines at cursor line. (NANSI)
ESC[nM Deletes n lines including cursor line. (NANSI)
ESC[n@ Inserts n blank chars at cursor. (NANSI)
ESC[nP Deletes n chars including cursor char. (NANSI)
ESC[n;ny Output char translate (NANSI)
When first char is encountered in output request, it
is replaced with the second char. When no parameters
are given, all chars are reset.
ESC["str"p Keyboard Key Reassignment. The first char of str gives
the key to redefine; the rest of the string is the
key's new value. To specify unprintable chars, give
the ASCII value of the char outside of quotes, as a
normal parm. IBM function keys are two byte strings.
Ex: ESC[0;";dir a:";13;p
redefines F1 to have the value "dir a:" followed by CR.
If no parameters given, all keys are reset to their
default values. Single or double quotes are valid.
ESC[n;n;...nm Set Graphics Rendition is used to set attributes as
well as foreground and background colors. If multiple parameters
are used, they are executed in sequence, and the effects are
cumulative. 'n' is one of the following attributes or colors:
0 All attributes off 5 Blink
1 Bold 7 Reverse Video
2 Dim 8 Invisible
4 Underline
%Foreground colors Background colors
30 Black 40 Black
31 Red 41 Red
32 Green 42 Green
33 Yellow 43 Yellow
34 Blue 44 Blue
35 Magenta 45 Magenta
36 Cyan 46 Cyan
37 White 47 White
ESC[=nh Set mode (see screen modes for n)
ESC[=nl Reset Mode (see screen modes for n)
^Screen modes are similar to those found in the IBM BIOS:
0 text 40x25 Black & White
1 text 40x25 Color
2 text 80x25 Black & White
3 text 80x25 Color
4 320x200 4 bits/pixel
5 320x200 1 bit/pixel
6 640x200 1 bit/pixel
7 cursor wrap
13 320x200 4 bits/pixel (EGA)
14 640x200 4 bits/pixel (EGA)
16 640x350 4 bits/pixel (EGA)
- for more information see ANSI document x3.64 or DOS manual
:byte ordering
^Byte Ordering of Different Computer Architectures
% 16 Bit 32 Bit Floating
%Architecture Integer Format Point
MC68000 MSB MSB MSB
Intel LSB LSB LSB
PDP-11 LSB MSW...LSW MSW...LSW
VAX LSB LSB MSW...LSW
IBM 360/370 MSB MSB MSB
MSB means Most Significant Byte first or a byte order of 3210
LSB means Least Significant Byte first or a byte order of 0123
MSW...LSW means a byte order of 3201 or 67452301
See "Computer Language Magazine", April, 1987, P.J. Plauger for
more information
:cold boot:post
^POST - Cold Boot / Power On Self Test Activities
- power supply starts Clock Generator (8284) with Power
Good signal on BUS
- CPU reset line is pulsed resetting CPU
- DS, ES, and SS are cleared to zero
%Cold and Warm Boot both execute the following sequence
- CS:IP are set to FFFF:0000 (address of ROM POST code)
- jump to CS:IP (execute POST, Power On Self test)
- interrupts are disabled
- CPU flags are set, read/write/read test of CPU registers
- checksum test of ROM BIOS
- Initialize DMA (verify/init 8237 timer, begin DMA RAM refresh)
- save reset flag then read/write test the first 32K of memory
- Initialize the Programmable Interrupt Controller (8259)
and set 8 major BIOS interrupt vectors (interrupts 10h-17h)
- determine and set configuration information
- initialize/test CRT controller & test video memory (unless 1234h
found in reset word)
- test 8259 Programmable Interrupt Controller
- test Programmable Interrupt Timer (8253)
- reset/enable keyboard, verify scan code (AAh), clear keyboard,
check for stuck keys, setup interrupt vector lookup table
- hardware interrupt vectors are set
- test for expansion box, test additional RAM
- read/write memory above 32K (unless 1234h found in reset word)
- addresses C800:0 through F400:0 are scanned in 2Kb blocks in
search of valid ROM. If found, a far call to byte 3 of the ROM
is executed.
- test ROM cassette BASIC (checksum test)
- test for installed diskette drives & FDC recalibration & seek
- test printer and RS-232 ports. store printer port addresses
at 400h and RS-232 port addresses at 408h. store printer
time-out values at 478h and Serial time-out values at 47Ch.
- NMI interrupts are enabled
- perform INT 19 (bootstrap loader), pass control to boot record or
cassette BASIC if no bootable disk found
- WARM BOOT procedure is now executed
- see INT 19 WARM BOOT DIAGNOSTIC CODES
:cpu
^CPU Characteristics / Determination
8088,80188,V20 six byte prefetch queue, allows use of self
modifying code to determine length of prefetch
8086,80186,V30 four byte prefetch queue, allows use of self
modifying code to determine length of prefetch
8088,8086,80188,81086,v20,v30 Flag register bits 12
through 15 cannot be cleared
8088,8086 will shift left or right using all 8 bits of CL
if CL = 33, register is guaranteed to be cleared
80188,80186,80286,80386 will shift left or right using only
lower 5 bits of CL. If CL = 32, the shift will not occur
80286,80386 earlier CPU's decremented SP before a PUSH SP,
but 286+ pushes the value first then, decrements SP
8088,8086 non-zero multiplication result clears zero flag
V20,V30 non-zero multiplication result does not clear zero
flag, set ZF before multiply, and test after, if it's
still set, then it's a V20, V30
80286 allows setting of bit 15 of the flags register
80386 allows setting of bits 12 through 14 of flags register
- source PC Tech Journal, "Chips In Transition", April 1986
:detecting:detection:determine
^Detecting ANSI.SYS
Compare segment address of a DOS interrupt with the segment of the
standard CON device. If equal, then ANSI is not loaded. If the
segment address of CON is greater than the DOS interrupt, then ANSI
is loaded or a TSR is handling the interrupt.
- see INT 21,52 for info on CON device address
^Detecting DESQView
1. call INT 2F with AX = DE00h
2. if AL = FF on return DESQView is installed
^Detecting Disk Ready
1. use INT 13 function 4 (Verify Sector) to check ready for read
2. check for error in AH of:
80h Time out, or Not Ready
AAh Drive not ready
00h drive is ready for reading
other value indicates drive is ready, but an error occurred
3. use INT 13,2 (Read Sector) followed by INT 13,3 (Write Sector)
to check ready for read/write. First read sector, test for
ready; write sector back, check for 03h (write protect) or
any of the other BIOS disk errors
- multiple attempts should be made to allow for disk motor startup
- allows testing of drive ready bypassing DOS and critical error
- see INT 13,2 INT 13,3 INT 13,4 and INT 13,STATUS
^Detecting Drive Existence
1. save current drive (INT 21,19)
2. set current drive (INT 21,E)
3. get current drive (INT 21,19)
4. if current drive == drive requested
then drive exists
else drive doesn't exist
5. reset original drive (INT 21,E)
- no critical error is generated if invalid drive is selected
^Detecting EGA Video
INT 10h, function 12h (in AL), subfunction 10h (in BL) will
return BL = 10h if not an EGA since invalid functions requests
return without register modification
- see INT 10,12h
^Detecting VGA Video
INT 10h function 1Ah can be used to detect the presence of VGA.
BL = 7 VGA with analog monochrome display
= 8 VGA with analog color display
- some enhanced EGA adapters will incorrectly identify as VGA
when INT 10,1B is used
- see INT 10,1A
^Detecting Extended Keyboard BIOS
1. use INT 16,5 to stuff FFFF into the keyboard buffer
2. use INT 16,10 to read the keystrokes back
3. if the data stuffed into the keyboard is returned within 16
extended reads, the BIOS handles the extended keyboard
4. byte at 40:96 is another method of detecting extended BIOS but
is not reliable since some compatibles give false positives
- see INT 16,5 INT 16,10 BIOS DATA AREA INT 9
^Detecting present of Expanded Memory Manager
1. attempt to open file/device 'EMMXXXX0' using INT 21h
function 3Dh; if successful continue, else no EMM
2. make sure EMMXXXX0 is a character device and not a disk file
by using IOCTL function 0 (Get Device Info); bit 7 of DX
should be set for char device and clear for disk file
3. make sure Expanded Memory Manager is available using IOCTL
function 7 (Get Output Status); AL should be non-zero (FF)
if Memory Manager is available, and zero if not available.
4. call INT 67,46 to get version information
- see also INT 21,3D IOCTL,0 IOCTL,7 INT 67,46
^Detecting Existence of Mouse Driver
1. check INT 33 vector is not 0:0
2. check INT 33 vector does not point to an IRET
3. call INT 33,0 to reset the mouse and get installed state
4. call INT 33,24 to check version, type and IRQ
^Detecting Miscellaneous
Boot drive; see INT 21,33 (DOS 4.0+)
CPU type; see CPU
Hardware configuration; see INT 11
Logical Drive Assignment; see IOCTL,E
Memory size, Base; see INT 12
Memory size, Extended; see CMOS
Micro Channel Bus on PS/2; see INT 15,C0
Network or Local Disk; see IOCTL,9
Network or Local File; see IOCTL,A
Parallel ports; see BIOS DATA AREA locations 40:08-40:0F
RAM Disk; see INT 21,32 and MEDIA DESCRIPTOR
Redirection on command line; see IOCTL,0
Removable media; INT 21,1B INT 21,1C
MEDIA DESCRIPTOR BYTE and IOCTL,8
Serial ports; see BIOS DATA AREA locations 40:00-40:07
Single drive A: or B: selection; see BIOS DATA AREA byte 50:04
SUBST'ed drive; see INT 21,32
Video Screen Size in Columns; see INT 10,F
Video Screen Size in Rows; see INT 10,11 subfunction 30h (EGA+)
APPEND resident; see INT 2F,0
ASSIGN resident; see INT 2F,0
DOSSHELL resident; see INT 2F,0
NLSFUNC resident; see INT 2F,0
PRINT resident; see INT 2F,0
SHARE resident; see INT 2F,0
:dbase files:dbf files
^dBASE - File Header Structure (dBASE II)
%Offset Size Description
00 byte dBASE version number 02h=dBASE II
01 word number of data records in file
03 byte month of last update
04 byte day of last update
05 byte year of last update
06 word size of each data record
08 512bytes field descriptors (see below)
520 byte 0Dh if all 32 field descriptors used; otherwise 00h
- dBASE II file header has a fixed size of 521 bytes
^DBASE - File header structure (DBASE III)
%Offset Size Description
00 byte dBASE vers num 03h=dBASE III w/o .DBT
83h=dBASE III w .DBT
01 byte year of last update
02 byte month of last update
03 byte day of last update
04 dword long int number of data records in file
08 word header structure length
10 word data record length
12 20bytes version 1.0 reserved data space
32-n 32bytes ea. field descriptors (see below)
n+1 byte 0dH field terminator.
- unlike dBASE II, dBASE III has a variable length header
^dBASE - Field Descriptors
%dBASE II Field Descriptors (header contains 32 FDs)
%Offset Size Description
00 11bytes null terminated field name string, 0Dh as first
byte indicates end of FDs
11 byte data type, Char/Num/Logical (C,N,L)
12 byte field length
13 word field data address, (set in memory)
15 byte number of decimal places
%dBASE III Field Descriptors (FD count varies):
%Offset Size Description
00 11bytes null terminated field name string
11 byte data type, Char/Num/Logical/Date/Memo
12 dword long int field data address, (set in memory)
16 byte field length
17 byte number of decimal places
18 14bytes version 1.00 reserved data area
:file handles:default handles:handles
^DOS Default/Predefined File Handles
0 - Standard Input Device - can be redirected (STDIN)
1 - Standard Output Device - can be redirected (STDOUT)
2 - Standard Error Device - can be redirected (STDERR)
3 - Standard Auxiliary Device (STDAUX)
4 - Standard Printer Device (STDPRN)
%See the following INT 21h Handle related function calls:
INT 21,3C - Create file using handle
INT 21,3D - Open file using handle
INT 21,3E - Close file using handle
INT 21,3F - Read file or device using handle
INT 21,40 - Write file or device using handle
INT 21,41 - Delete file
INT 21,42 - Move file pointer using handle
INT 21,43 - Change file mode
INT 21,45 - Duplicate file handle
INT 21,46 - Force duplicate file handle
INT 21,56 - Rename file
INT 21,57 - Get/set file date and time using handle
INT 21,5A - Create temporary file (3.x+)
INT 21,5B - Create new file (3.x+)
INT 21,67 - Set handle count (3.3+)
INT 21,68 - Flush buffer (3.3+)
- STDIN, STDOUT and STDERR can be redirected
- maximum number of files available to all DOS processes at one
time is defined by the FILES=N statement of CONFIG.SYS
- maximum number of files available to an application is N-3 where
N is derived from the CONFIG.SYS FILES=N statement minus the
count of handles used by other processes
- INT 21,67 can be used to increase the number of file handles for
an application to greater than 20; the max handle count is
still limited by the value of FILES= in CONFIG.SYS file
- see SFT INT 21 INT 21,52 INT 21,67
:numeric ranges:data ranges:ranges
^Numeric Ranges for Data Elements
% Size Range Significant digits
1 byte character -128 to 127 2
2 byte integer -32,768 to 32,767 4
4 byte integer -2,147,483,648 to 2,147,483,647 9
8 byte integer -9x10e18 to 9x10e18 18
4 byte real 8.43x10e-37 to 3.37x10e38 6-7
8 byte real 4.19x10e-307 to 1.67x10e308 15-16
10 byte real 3.4x10e-4932 to 1.2x10e4932 19
10 byte packed dec -99..99 to 99..99 18
:undocumented
^DOS Undocumented Interrupts, Functions and Structures
INT 21,1F Get pointer to current drive parameter table
INT 21,32 Get pointer to drive parameter table
INT 21,34 Get address to DOS critical flag (INDOS flag)
INT 21,37 Get/set switch char
INT 21,4B EXEC/Load and execute (Function 1 undocumented)
INT 21,50 Set current process id (DOS 2.x)
INT 21,51 Get current process id (DOS 2.x)
INT 21,52 Get pointer to DOS "INVARS"
INT 21,53 Generate drive parameter table
INT 21,55 Create new PSP
INT 21,58 Get/set memory allocation strategy (DOS 3.x+)
INT 21,5D Critical error information (DOS 3.x+)
INT 21,60 Get fully qualified file name (DOS 3.x+)
INT 21,64 Set device driver look ahead (DOS 3.3+)
INT 21,69 Get/set disk serial number (DOS 4.0+)
INT 21,F8 Set INT 21 OEM handler
INT 28 DOS idle loop/scheduler
INT 29 Fast character output
INT 2E Execute command using base level COMMAND.COM
BCB Batch Control Block
DTA Disk Transfer Area (partially undocumented)
MCB Memory Control Block
PSP Program Segment Prefix Layout (partially undocumented)
SFT System File Table
- the above items are undocumented with respect to IBM/Microsoft
and should be not be used unless one fully understands the
repercussions
- several functions are version dependant and OEM specific
:warm boot:bootstrap:reboot
^Warm Boot / System Bootstrap
- Ctrl-Alt-Delete results in a warm boot but only after part of the
POST sequence has executed. See COLD BOOT for more information.
- ROM BIOS bootstrap loader (int 19) attempts Boot Record load
- Drive A: is searched for a Boot Record, if no Boot Record is found
the active partition of the first drive is searched. If found, it
is loaded into memory at 7C00:0 and given control. If still not
found Cassette BASIC is loaded (IBM only) or a prompt for a system
diskette is displayed.
- the boot record code checks that IBMBIO.COM and IBMDOS.COM (IO.SYS
and DOS.SYS for MSDOS) exist and are the first two files. These
files must be contiguous and the first two directory entries.
- boot record loads IBMBIO.COM
- IBMBIO.COM initialization code loads IBMDOS.COM
∙ determines equipment status
∙ resets disk system
∙ initializes attached devices
∙ loads installable device drivers
∙ sets DOS relative interrupt vectors
∙ relocates IBMDOS.COM downward and begins its execution
- IBMDOS.COM initializes its working tables
∙ initializes DOS interrupt vectors for ints 20h through 27h
∙ builds PSP for COMMAND.COM at lowest possible segment
∙ interrupt vectors for ints 0Fh through 3Fh are initialized
(for DOS 3.1+)
∙ loads COMMAND.COM (or specified command interpreter) using the
EXEC call.
- AUTOEXEC.BAT is then loaded and executed
- see BOOT RECORD INT 19 COLD BOOT
