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1FORMAT - formats a new disk, clears the FAT and DIRECTORY
2and optionally copies the SYSTEM and COMMAND.COM to this
3new disk.
4
5Command syntax:
6
7 FORMAT [drive:][/switch1][/switch2]...[/switch16]
8
9 Where "drive:" is a legal drive specification and if
10 omitted indicates that the default drive will be used.
11 There may be up to 16 legal switches included in the
12 command line.
13
14
15 The OEM must supply five (NEAR) routines to the program
16along with 6 data items. The names of the routines are INIT,
17DISKFORMAT, BADSECTOR, WRTFAT and DONE, and their flow of
18control (by the Microsoft module) is like this:
19
20 |
21 +---------+
22 | INIT |
23 +---------+
24 |
25 |<------------------------------+
26+------------+ |
27| DISKFORMAT | |
28+------------+ |
29 |<-------+ |
30+-----------+ |-This loop is done |- This loop done
31| BADSECTOR | | for each group of | once for each disk
32+-----------+ | bad sectors | to be formatted.
33 |----->--+ | If variable HARDFLAG
34 | | is set then the loop
35+----------+ | is only performed
36| | | once.
37| WRTFAT | |
38+----------+ |
39 | |
40 +------+ |
41 | DONE | |
42 +------+ |
43 +---->--------------------------+
44
45 The INIT, DISKFORMAT, and BADSECTOR routines are free
46to use any MS-DOS system calls, except for calls that cause
47disk accesses on the disk being formatted. DONE may use
48ANY calls, since by the time it is called the new disk has
49been formatted.
50
51The following data must be declared PUBLIC in a module
52provided by the OEM:
53
54 SWITCHLIST - A string of bytes. The first byte is count
55 N, followed by N characters which are the switches to
56 be accepted by the command line scanner. Alphabetic
57 characters must be in upper case (the numeric
58 characters 0-9 are allowed). The last three switches,
59 normally "O", "V" and "S", have pre-defined meanings.
60
61 The "S" switch is the switch which causes the
62 system files IO.SYS, MSDOS.SYS, and COMMAND.COM to be
63 transfered to the disk after it is formatted thus
64 making a "S"ystem disk. The switch can be some letter
65 other than "S", but the last switch in the list is
66 assumed to have the meaning "transfer system",
67 regardles of what the particular letter is.
68
69 The second to the last switch, "V", causes FORMAT
70 to prompt the user for a volume label after the disk
71 is formatted. Again, as with "S", the particular
72 letter is not important but rather the position in the
73 list.
74
75 The third to the last switch, "O", causes FORMAT to
76 produce an IBM Personal Computer DOS version 1.X
77 compatible disk. Normally FORMAT causes a 0 byte to
78 be placed in the first byte of each directory entry
79 instead of the 0E5 Hex free entry designator. This
80 results in a very marked directory search performance
81 increase due to an optimization in the DOS. Disks
82 made this way cause trouble on IBM PC DOS 1.X
83 versions, however, which did not have this
84 optimization. The 0 byte fools IBM 1.X versions into
85 thinking these entries are allocated instead of free,
86 NOTE that IBM Personnal Computer DOS version 2.00 and
87 MS-DOS version 1.25 will have no trouble with these
88 disks, since they have the same optimization. The "O"
89 switch causes FORMAT to re-do the directory with a 0E5
90 Hex byte at the start of each entry so that the disk
91 may be used with 1.X versions of IBM PC DOS, as well
92 as MS-DOS 1.25/2.00 and IBM PC DOS 2.00. This switch
93 should only be given when needed because it takes a
94 fair amount of time for FORMAT to perform the
95 conversion, and it noticably decreases 1.25 and 2.00
96 performance on disks with few directory entries.
97
98 Up to 16 switches are permitted. Normally a "C"
99 switch is specified for "Clear". This switch should
100 cause the formatting operation to be bypassed (within
101 DISKFORMAT or BADSECTOR). This is provided as a
102 time-saving convenience to the user, who may wish
103 to "start fresh" on a previosly formatted and used
104 disk.
105
106 HARDFLAG - BYTE location which specifies whether the
107 OEM routine is formatting a fixed disk or a a drive
108 with removable media. A zero indicates removable
109 media, any other value indicates a fixed disk. The
110 status of this byte only effect the messages printed
111 by the main format module. This value should be
112 set or reset by the OEM supplied INIT routine.
113
114 FATID - BYTE location containing the value to be used
115 in the first byte of the FAT. Must be in the range
116 F8 hex to FF hex.
117
118 STARTSECTOR - WORD location containing the sector number
119 of the first sector of the data area.
120
121 FATSPACE - WORD location containing the address of the
122 start of the FAT area. A FAT built in this area
123 will be written to disk using the OEM supplied WRTFAT
124 subroutine. 6k is sufficient to store any FAT. This
125 area must not overlap the FREESPACE area.
126
127 FREESPACE - WORD location which contains the address
128 of the start of free memory space. This is where
129 the system will be loaded, by the Microsoft module,
130 for transferring to the newly formatted disk. Memory
131 should be available from this address to the end
132 of memory, so it is typically the address of the
133 end of the OEM module.
134
135The following routines must be declared PUBLIC in the
136OEM-supplied module:
137
138 INIT - An initialization routine. This routine is called
139 once at the start of the FORMAT run after the switches
140 have been processed. This routine should perform
141 any functions that only need to be done once per
142 FORMAT run. An example of what this routine might
143 do is read the boot sector into a buffer so that
144 it can be transferred to the new disks by DISKFORMAT.
145 If this routine returns with the CARRY flag set it
146 indicates an error, and FORMAT will print "Format
147 failure" and quit. This feature can be used to detect
148 conflicting switches (like specifying both single
149 and double density) and cause FORMAT to quit without
150 doing anything.
151
152 DISKFORMAT - Formats the disk according to the options
153 indicated by the switches and the value of FATID
154 must be defined when it returns (although INIT may
155 have already done it). This routine is called once
156 for EACH disk to be formatted. If neccessary it
157 must transfer the Bootstrap loader. If any error
158 conditions are detected, set the CARRY flag and return
159 to FORMAT. FORMAT will report a 'Format failure'
160 and prompt for another disk. (If you only require
161 a clear directory and FAT then simply setting the
162 appropriate FATID, if not done by INIT, will be all
163 that DISKFORMAT must do.)
164
165 BADSECTOR - Reports the sector number of any bad sectors
166 that may have been found during the formatting of
167 the disk. This routine is called at least once for
168 EACH disk to be formatted, and is called repeatedly
169 until AX is zero or the carry flag is set. The carry
170 flag is used just as in DISKFORMAT to indicate an
171 error, and FORMAT handles it in the same way. The
172 first sector in the data area must be in STARTSECTOR
173 for the returns from this routine to be interpreted
174 correctly. If there are bad sectors, BADSECTOR must
175 return a sector number in in register BX, the number
176 of consecutive bad sectors in register AX, and carry
177 clear. FORMAT will then process the bad sectors
178 and call BADSECTOR again. When BADSECTOR returns
179 with AX = 0 this means there are no more bad sectors;
180 FORMAT clears the directory and goes on to DONE,
181 so for this last return BX need not contain anything
182 meaningful.
183
184 FORMAT processes bad sectors by determining their
185 corresponding allocation unit and marking that unit
186 with an FF7 hex in the File Allocation Table. CHKDSK
187 understands the FF7 mark as a flag for bad sectors
188 and accordingly reports the number of bytes marked
189 in this way.
190
191 NOTE: Actual formatting of the disk can be done in
192 BADSECTOR instead of DISKFORMAT on a "report as you
193 go" basis. Formatting goes until a group of bad
194 sectors is encountered, BADSECTOR then reports them
195 by returning with AX and BX set. FORMAT will then
196 call BADSECTOR again and formatting can continue.
197
198 WRTFAT - This routine is called after the disk is
199 formatted and bad sectors have been reported. Its
200 purpose is to write all copies of the FAT from the
201 area of memory referenced by FATSPACE to the drive
202 just formatted. It may be possible to use INT 26H
203 to perform the write, or a direct BIOS call. Whether
204 this is possible depends on whether the FAT ID byte
205 is used by the BIOS to determine the media in the
206 drive. If it is, these methods will probably fail
207 because there is no FAT ID byte on the disk yet (in
208 this case WRTFATs primary job is to get the FAT ID
209 byte out on the disk and thus solve the chicken and
210 egg problem).
211
212 DONE - This routine is called after the formatting is
213 complete, the disk directory has been initialized,
214 and the system has been transferred. It is called
215 once for EACH disk to be formatted. This gives the
216 chance for any finishing-up operations, if needed.
217 If the OEM desires certain extra files to be put
218 on the diskette by default, or according to a switch,
219 this could be done in DONE. Again, as in BADSECTOR
220 and DISKFORMAT, carry flag set on return means an
221 error has occurred: 'Format failure' will be printed
222 and FORMAT will prompt for another disk.
223
224
225The following data is declared PUBLIC in Microsoft's FORMAT
226module:
227
228 SWITCHMAP - A word with a bit vector indicating what
229 switches have been included in the command line. The
230 correspondence of the bits to the switches is
231 determined by SWITCHLIST. The right-most
232 (highest-addressed) switch in SWITCHLIST (which must
233 be the system transfer switch, normally "S")
234 corresponds to bit 0, the second from the right,
235 normally "V" to bit 1, etc. For example, if
236 SWITCHLIST is the string "7,'AGI2OVS'", and the user
237 specifies "/G/S" on the command line, then bit 6 will
238 be 0 (A not specified), bit 5 will be 1 (G specified),
239 bits 4,3,2 and 1 will be 0 (neither I,2,O or V
240 specified), and bit 0 will be 1 (S specified).
241
242 Bits 0,1 and 2 are the only switches used in
243 Microsoft's FORMAT module. These switches are used 1)
244 after INIT has been called, to determine if it is
245 necessary to load the system; 2) after the last
246 BADSECTOR call, to determine if the system is to be
247 written, E5 directory conversion is to be done, and/or
248 a volume label is to be asked for. INIT may force
249 these bits set or reset if desired (for example, some
250 drives may never be used as system disk, such as hard
251 disks). After INIT, the "S" bit may be turned off
252 (but not on, since the system was never read) if
253 something happens that means the system should not be
254 transferred.
255
256 After INIT, a second copy of SWITCHMAP is made
257 internally which is used to restore SWITCHMAP for
258 each disk to be formatted. FORMAT itself will turn
259 off the system bit if bad sectors are reported in
260 the system area; DISKFORMAT and BADSECTOR are also
261 allowed to change the map. However, these changes
262 affect only the current disk being formatted, since
263 SWITCHMAP is restored after each disk. (Changes
264 made to SWITCHMAP by INIT do affect ALL disks.)
265
266 DRIVE - A byte containing the drive specified in the
267 command line. 0=A, 1=B, etc.
268
269Once the OEM-supplied module has been prepared, it must linked
270with Microsoft's FORMAT.OBJ module and the FORMES.OBJ module.
271If the OEM-supplied module is called OEMFOR.OBJ, then the
272following linker command will do:
273
274 LINK FORMAT FORMES OEMFOR;
275
276This command will produce a file called FORMAT.EXE. FORMAT
277has been designed to run under MS-DOS as a simple binary
278.COM file. This conversion is performed by LOCATE (EXE2BIN)
279with the command
280
281 LOCATE FORMAT.EXE FORMAT.COM
282
283which will produce the file FORMAT.COM.
284
285;*****************************************
286;
287; A Sample OEM module
288;
289;*****************************************
290
291CODE SEGMENT BYTE PUBLIC 'CODE'
292; This segment must be
293; named CODE, it must be
294; PUBLIC, and it's
295; classname must be 'CODE'
296
297
298 ASSUME CS:CODE,DS:CODE,ES:CODE
299
300; Must declare data and routines PUBLIC
301
302PUBLIC FATID,STARTSECTOR,SWITCHLIST,FREESPACE
303PUBLIC INIT,DISKFORMAT,BADSECTOR,DONE,WRTFAT
304PUBLIC FATSPACE,HARDFLAG
305
306; This data defined in Microsoft-supplied module
307
308 EXTRN SWITCHMAP:WORD,DRIVE:BYTE
309
310INIT:
311
312; Read the boot sector into memory
313 CALL READBOOT
314 ...
315; Set FATID to double sided if "D" switch specified
316 TEST SWITCHMAP,10H
317 JNZ SETDBLSIDE
318 ...
319 RET
320
321DISKFORMAT:
322 ...
323
324; Use the bit map in SWITCHMAP to determine
325; what switches are set
326
327 TEST SWITCHMAP,8 ;Is there a "/C"?
328 JNZ CLEAR ; Yes -- clear operation
329 ; requested jump around the
330 ; format code
331 < format the disk >
332CLEAR:
333 ...
334; Transfer the boot from memory to the new disk
335 CALL TRANSBOOT
336 ...
337 RET
338
339; Error return - set carry
340
341ERRET:
342 STC
343 RET
344
345BADSECTOR:
346 ...
347 RET
348
349
350WRTFAT:
351 ...
352
353WRTFATLOOP:
354 < Set up call to write out a fat to disk>
355 ...
356 MOV BX,[FATSPACE]
357
358 < Write out one fat to disk>
359 JC ERRET
360 ...
361 < Decrement fat counter >
362 JNZ WRTFATLOOP
363 CLC ;Good return
364 RET
365
366
367DONE:
368 ...
369 RET
370
371; Default Single sided
372FATID DB 0FEH
373
374HARDFLAG DB 0
375
376STARTSECTOR DW 9
377
378SWITCHLIST DB 5,"DCOVS" ; "OVS" must be the last
379 ; switches in the list
380
381FATSPACE DW FATBUF
382
383FREESPACE DW ENDBOOT
384
385BOOT DB BOOTSIZE DUP(?) ; Buffer for the
386 ; boot sector
387
388FATBUF DB 6 * 1024 DUP(?) ; Fat buffer
389ENDBOOT LABEL BYTE
390
391CODE ENDS
392 END
393
HIC SVNT DRACONES