STEP13

by

Mike Parker
2374 Meadowpark Court
Maryland Heights, MO 63043


CIS 70270,161

11/19/87
Version 1.0

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Program Description
============================================================

STEP13 is a Terminate and Stay Resident program that intercepts BIOS
interrupt 13H. Each time an INT 13H is called, a 'pop-up window' is
displayed with a description of what the BIOS call is about to do
along with a display of the input parameters (drive #, track, sector, etc.).

STEP13 detects whether a CGA or Monochrome adapter is installed and will
determine which video page is currently active each time it puts up the
information window.

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Program Execution
============================================================

To load STEP13 type:
STEP13
followed by pressing the return key.

The program will install itself, display a message such as:
STEP13 Version x.x Installed
and return to the DOS prompt.

STEP13 will be in memory intercepting INT 13h calls but will not display
the status window until it is 'armed'. This way STEP13 can be loaded at
any time without immediately stopping program execution.

To 'arm' STEP13 hold BOTH THE LEFT AND RIGHT "SHIFT" KEYS DOWN SIMULTANEOUSLY
then release them. These keys are usually located to the left and right
of the SPACE BAR and one row above it.

To invoke the STEP13 display some disk activity must be generated so put a
floppy disk in drive 'A' and type:
DIR A:
followed by the return key.

Just before the disk is accessed a window will pop up showing something like:

+------------------------------------+
| Int 13H - Function 02H |
| |
| Read 01 Disk Sector(s) |
| |
| Drive: 00H |
| Head: 00 |
| Track: 000 | |
| Sector: 02 |
| Buffer Address = XXXX:XXXXH |
| |
| Skip Current Func Return Code |
| ESC - Non Stop xxxx - Move Window |
+------------------------------------+

Press any key except 'S', 'R', the ARROW keys or 'ESCAPE' to execute the
BIOS function.


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Program Options
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Skip Current Function
---------------------
To keep you from having to press a key each time to execute a long sequence
of one type of function (read, write, etc.) you can use the 'Skip Current
Func' option. This tells STEP13 to run nonstop as long as the current
function (in this case 02h, or READ) is being repeated by the calling program.
When a function code other than 02h is executed, STEP13 will resume display.


Return Code
-----------
When the STEP13 window is displayed, press the 'R' key and you will see:

+------------------------------------+
| Int 13H - Function 02H |
| |
| |
| |
| Return Code = 0000H |
| Carry Flag = 0 |
| Zero Flag = 0 | |
| |
| |
| |
| Press Any Key |
| To Continue |
+------------------------------------+

This is the result immediately after the INT 13h code is executed.
The 'Return Code' is what was returned in the 'AX' register.


ESC - NON STOP
--------------
Pressing the ESCAPE key while the window is displayed will prevent STEP13
from stopping on subsequent BIOS calls, in effect "dis-arming" itself.
STEP13 will not be removed from memory and it will still intercept the
INT 13h vector but after testing a flag it will restore the user's
registers and continue on with the BIOS function.

To "re-arm' STEP13 hold BOTH THE LEFT AND RIGHT "SHIFT" KEYS DOWN
simultaneously then release them. When the next INT 13h call is made
STEP13 will resume display of its window.


ARROW KEYS - MOVE WINDOW
------------------------
If the window is covering up a part of the screen you would like to see,
press one of the cursor positioning keys on the numeric keypad and the
window will move.
The four arrow keys will move the window one position.
The HOME, PGUP, END and PGDN keys will move the window to the corners of
the screen.


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Program Removal
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To completely remove STEP13 from memory hold down the following three keys:
CONTROL LEFT-SHIFT RIGHT-SHIFT

Hold them all down simultaneously then release them.

STEP13 will not be removed immediately. Rather, when DOS is in its idle
loop waiting for a key to be pressed at the command line prompt, INT 28h
will be intercepted. If the above sequence of three keys has been pressed,
all of the memory allocated for STEP13 will be released and all intercepted
vectors will be restored.