CS401 Computer Architecture and Assembly Language Assignmnet 6 Deadline 22 July 2010

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Assignment

Write assembly language program that get the attribute of an existing file and also modify its hidden attribute.

What to Submit:
Submit Microsoft Word document containing the assembly language code for the above mentioned program.

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That's good to know this assignment has been uploaded. Lets see what happen.

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hona kiya hai dear all the same jasy har assignment main hota hia

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13.3.8.12 Change/Get File Attributes
Function (ah): 43h
Entry parameters:
al- Subfunction code
0- Return file attributes in cx
1- Set file attributes to those in cx
cx- Attribute to be set if AL=01
ds:dx- address of pathname
Exit parameters:
If carry set,
ax contains one of the following error codes:
1- Invalid function
3- Pathname not found
5- Access denied
If the carry is clear and the subfunction was zero,
cx will contain the file's attributes.
This call is useful for setting/resetting and reading a file's attribute bits. It can be used to set a file to read-only, set/clear the archive bit, or otherwise mess around with the file attributes.



2nd code
To create a file if it does not exist or leave it on 0 length if it exists, Handle.
Call registers:
AH = 3CH
CH = File attribute
DSX = Pointer to an ASCII specification.
Return registers:
CF = 0 and AX the assigned number to handle if there is no error, in case there is, CF ill be 1 and AX will contain the error code: 3 path not found, 4 there This function substitutes the 16H function. The name of the file is specified on an ASCII chain, which has as a characteristic being a conventional chain of bytes ended with a 0 character.
The file created will contain the attributes defined on the CX register in the following manner:
Value Attributes
00H Normal
02H Hidden
04H System
06H Hidden and of system
The file is created with the reading and writing permissions. It is not possible to create directories using this function.



3rdcode

Create/Truncate File

C:\>debug
-a 0100
xxxx:0100 mov ah,3c     ;Create file func.
xxxx:0102 mov cx,2      ;Archive file attribute
xxxx:0105 mov dx,010f   ;Points to filename
xxxx:0108 int 21        ;Do it
xxxx:010A mov ax,4c00
xxxx:010D int 21
xxxx:010F db "C:\Users\jakash3\newfile1.txt",00
-n mkf.com
-r cx
CX 0000
:002D
-w

Writing 001A bytes.
-q
Note:
File attributes are specified by the hex value of a bit array.
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| ? | ? | ? | 0 | 0 | ? | 0 | 0 |
+---+---+---+---+---+---+---+---+
0 – Read Only
1 – Hidden
2 – System
3 – Volume label (ignored)
4 – Reserved, must be zero (directory)
5 – Archive
6 – Unused
7 – Unused
A Read-Only Archive file: 10000100
In hex that would be: 84
So 84 would be the value for CX in the 3C function of Int 21.

4th code.
File Attributes

Bit Hex Description
7 6 5 4 3 2 1 0
. . . . . . . 1 01 Read-only
. . . . . . 1 . 02 Hidden
. . . . . 1 . . 04 System
. . . . 1 . . . 08 Volume label
. . . 1 . . . . 10 Directory
. . 1 . . . . . 20 Archive

Read-only Files that are marked as read-only can be read, but
not altered. Attempts to open read-only files for
output, or to create a file with the same name,
result in an error. Read-only files do appear in
normal directory searches, however.

Hidden Hidden files do not appear in DOS's directory
listings, nor do they appear in normal file
searches.

System Marks files that are used by the system, such as
IBMBIO.COM and IBMSYS.COM. Such files do not appear
in normal file searches.

Volume label Used for the 11-character volume label on a disk.
All other information in a volume label's directory
entry is ignored. Volume labels are not files, per
se--they use one entry in the directory, but have no
additional data.

Directory The directory entry refers to a subdirectory.
Subdirectories are normally excluded from file
searches.

Archive This bit, when set, indicates that the file has been
changed since the last time it was backed up. This
bit is set whenever a file is written to and then
closed.

Bits 6, 7 These bits are reserved for future use and must be
set to 0.

--------------------------------------------------------------------------

Notes: File searches with the search attribute set to 0
will find all files with no attribute, or files with
the read-only and/or archive attribute set.

The directory and volume-label bits cannot be
changed using the CHMOD function (43h) DOS call.