Contents of the SHOW87.DOC file
SHOW87 Version 1.10
Copyright (c) 1987-1988 Eric Tauck
All Rights Reserved
SHOW87 is a memory resident program that displays the entire state of an
installed 8087 coprocessor chip. This program will only work if an 8087 is
present. SHOW87 (or a program like it) is very useful when debugging code
that contains 8087 instructions.
SHOW87 has two modes of installation. The default is the shell mode in which
SHOW87, rather than making itself truly resident, executes a DOS shell. This
allows you to deinstall SHOW87 by typing EXIT at any DOS prompt. The
disadvantage of the shell mode is that a second command processor must be
invoked, which uses an extra 3000 to 4000 bytes of memory. The other type of
installation is the resident mode, which is specified by the /R parameter.
SHOW87 uses less memory in this mode, but cannot be removed. SHOW87 alone
uses about 5600 bytes of memory.
Once installed, the program may be invoked at any time by pressing ALT-7.
Invoking SHOW87 causes most of the upper half of the screen to display the
flags, registers, and other information regarding the 8087. Pressing any key
exits the display and restores the screen. The normal sequence of events is
to install SHOW87 before debugging 8087 code and then removing SHOW87 when it
is not needed any longer.
If SHOW87 cannot properly install itself, it will display an error message and
terminate. The most common reasons for such an error are insufficient memory
and COMMAND.COM not found. COMMAND.COM is only needed when SHOW87 is run in
the shell mode. SHOW87 finds the COMMAND.COM file by looking for the COMSPEC
parameter in the environment (see your DOS manual).
SHOW87 displays all 8087 information, including the instruction pointer, the
operand pointer, the operation code; the control, status, and tag words; the
precision, rounding, and infinity control settings; the stack top; the
condition codes and their various interpretations; the exception settings and
interrupt mask settings; and the register values.
The condition code settings represent C3, C2, C1, and C0 respectively. The
Comp, Test, and Exam fields display the meaning of the condition codes as
returned by the FCOM, FTST, and FXAM instructions.
Register values are displayed in one of two ways. If the number has a tag
setting of VALID, the number is displayed in decimal format. If the number
has a tag setting of SPECIAL or EMPTY, a hexadecimal dump of the number is
displayed. After the mantissa and exponent, the type of value (as interpreted
by the FXAM instruction) is displayed.