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Programming Languages Suite
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ProgLangD.iso
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Assembly
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READ.ME
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1979-12-31
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About the Diskette
This diskette contains both the .ASM and .COM versions of all
the end-of-chapter examples in the book Advanced Assembly Language for
the IBM PC. In the order they appear in both the book and on the
diskette, these programs are: LOCK, UNLOCK, KEEPER, DIREX, PHOTO,
CACHE, and LOCATE. In general, the use of these programs is kept
straightforward, making the programs easy to use. Here is an overview
of each program.
LOCK and UNLOCK
This pair of programs let you encrypt files with medium
security (a determined specialist was able to break the code in about
28 hours of steady effort). To use them to lock a file named FILE.EXT,
just type "LOCK FILE.EXT FILE.SBL", where FILE.SBL will be the
scrambled version of the file. If you do not supply a second file name,
LOCK will name the file FILE.LOC.
LOCK will ask you to type a pass-phrase. Once you do, the file
will be encoded from a key made from the ASCII characters in the
phrase. To decode the file, type "UNLOCK FILE.SBL FILE.EXT", and
FILE.EXT will be regenerated. Be sure you type the SAME pass-phrase.
It is possible to double the security by encoding an
already-encoded file a second time, but make sure to use the
pass-phrases in reverse order of application.
KEEPER
KEEPER stores your DOS commands and lets you recall them. As
KEEPER.ASM is set up on the diskette, it uses ^N as a trigger key. To
install KEEPER, just run KEEPER.COM. If you want to recall some
previous DOS command, type a ^N. A reverse-video window will appear on
the screen with the last eight DOS commands. Using the cursor keys, you
can make the command you want to recall blink. When you type another
^N, the command is re-entered at DOS level and the window disappears.
If you don't want to choose any of the available commands, leave the
blinking cursor on the bottom line and type ^N. No DOS command will be
entered.
If you want to use a trigger key other than ^N, enter the scan
and ASCII codes of your trigger key into KEEPER.ASM in the one location
indicated and reassemble KEEPER.
DIREX
This utility is a directory manager. It has seven commands,
which appear on the bottom of the screen for reference. The rest of the
screen is filled with the file names of the current subdirectory. To
use DIREX, move the reverse-video cursor that highlights file names
around the screen with the cursor keys. You can select a number of
files and perform an operation on them en masse (protecting, deleting,
copying, etc.). To mark a files for further work, move the cursor to
their name and press the space bar. The file name will stay highlighted
when you move the cursor away. This file has now been marked. To unmark
a file, move the cursor to its name and press the space bar again.
After you have marked the files, you can delete them all at
once with the D command, protect them as read-only with P, unprotect
them with U, or copy them to a new path with C. When you press C, DIREX
asks you for the path name the files are to be copied to (e.g., B: or
C:\ARCHIVE). You can work on the files in any subdirectory by using the
N, or new directory command. When you press N, DIREX will ask you for a
new path name to make the default. To quit, use Q.
PHOTO
This utility is a small screen manager. It is a memory-resident
program that allows you to capture screens for later use, or to recall
a few select screens that you have created yourself. For example, if
you are assembling a file and there are some errors, you can save the
screen (with ^N as PHOTO.COM is set up), edit the file, and then, while
still in your editor, recall the screenful of errors with another key
(^F as PHOTO.COM is set up). Once the recalled screen is displayed,
touching any key restores the screen to its original condition (i.e.,
before you pushed ^N).
You can also install up to three of your own screens in memory,
to be recalled with other control characters (^A, ^B, and ^C as
PHOTO.COM is set up). When PHOTO.COM is run, it searches for the three
files A.DAT, B.DAT, and C.DAT, in that order. Each file should be
exactly 2000 bytes long. If they are not there, PHOTO will still run
without problem. If, however, they are there, they are loaded into
memory to be recalled at will. On this diskette is a sample file,
A.DAT, with a screenful of ASCII codes that can be recalled at any time
(by pressing ^A). To install your own trigger keys, simply enter the
correct scan and ASCII codes as marked in PHOTO.ASM and reassemble the
program.
CACHE
This program is a write-through disk cache system. It stores
the most frequently used sectors in memory. The next time these sectors
are read by some program, CACHE supplies them from memory instead of
reading them from the disk. It is a "write-through" cache because as
sectors get written, their copies in memory are updated as well.
This system is different from the buffers DOS uses, since the
buffers are flushed when a program exits. With CACHE, you can go
through the edit, assemble, and link cycle many times and save time
each time you do since CACHE always stays in memory.
As CACHE.COM is set up, it will store up to 64 sectors in
memory. You can change this by changing the one marked location in
CACHE.ASM (the minimum is 24 and the maximum is 124).
LOCATE
LOCATE tries to find character strings in files. If you type
"LOCATE This is a test.", LOCATE will try to find the character string
in all the files in the current subdirectory. If a match is made
(LOCATE is case-sensitive), the name of the file and the line in which
the match was found are both printed out.
Besides searching the current subdirectory, you can have LOCATE
search other directories as you require. To do this, place a file named
PATH.DAT in the main directory of the current disk. In this file, place
the names of the other paths you want LOCATE to search. Terminate each
path name, even the last one, with a <cr> <lf>. Here is a sample
PATH.DAT:
A:
\ARCHIVE
\RECORDS
LOCATE will read in PATH.DAT and search all the files in those paths
for the specified string as well.