V4N4 - Complang

ROMeble FORTH (continued from page 13)
in Figure 6. After assembling the code
for the interrupt service routines INT.0
through INT.7, an ACSEG directive is us-
ed to set the absolute compile pointer
to JBASE. The active ROM segment in-
dex is saved on the stack. Next the ac-
tual jump table is assembled, starting
at the address of JBASE. Finally, the
CSEG directive restores the previously
active ROM segment.
HERE, ALLOT, etc.
In traditional monolithic FORTH
implementations, the word HERE pro-
vides the next available dictionary ad-
dress (usually the contents of a variable
called DP). In proFORTH'", the word
HERE provides the next available ad-
dress in the active ROM segment. For
CSEG=O, this defaults to the active
dictionary segment. Similarly, the
word ALLOT allocates space in the
active ROM segment (or dictionary if
CSEG=o). In addition to HERE, pro-
3.
4.
FORTH'" provides the word VHERE to
obtain the next available address in the
active RAM segment. If VSEG=O,
VHERE provides the next available
address in the active dictionary just as
for HERE. Therefore, in its default mode
proFORTH'" remains completely
compatible with traditional FORTH,
but broadens in a consistently logical
way as segment control directives are
issued. This enables the user to have
complete control over where the compiler
stores each component of every
definition.
Conclusion
It is not possible, in an article of this
size, to even introduce all of the compilation
control mechanisms available
in proFORTH'". For example, we
have not discussed the subjects of
multiple dictionaries, extensions,
selective uurging of names, split system
definitions, etc. Insofar as ROM-
INTRODUCING P-FORTH PUTTING P-FORTH TO WORK:
able code compilation is concerned,
the principles discussed above apply to
all of these areas even though imple-
mentation details are often complex.
proFORTH'" logically extends and
broadens the meaning of the tradi-
tional FORTH words such as HERE and
ALLOT, so that the programmer is given
complete control over compilation
memory assignments. This is accom-
plished without giving up the tra-
ditional behavior of a monolithic
dictionary system if the user wishes to
program in that environment.
CODE 1m.0 ... RET, EkJD-CoDE
CODE Im.l ... RET, END-CoDE
CODE I"C.7 ... RET, CNbCom
JBAfE ACSEG
INT.o JMP, I 1m.1 J ~P, ... 1m.7 JMP.
CSEG
FIGURE 6 - DUCIPLI: OF ABSOLUTE EQIPIIATIOW
SOFTWARE
The P-FORTH Card is the key users interactively develop An interactive high-level
member in a family of control applications through a combi- language following the
systems cards offered by the nation of hardware and software. fig-FORTH model
innovators at Peopleware These applications are automatic- A monitor for system checkout
Systems, Inc. P-FORTH has four ally programmed into nonmajor
advantages:
volatile memory (EEROM). When "FORTH-type" Screen editor for
the applications are proven and d p ~ ~ ~ application ~ ~ : g
1. It is a versatile building block. functioning, a single switch
The simple addition of a transforms the system from the A iiFoRTH-type" assembler for
power supply and terminal developmental mode into the writing assembly language
makes the P-FORTH card both a target system.
routines
low cost development system
as well as a target system.
High-level interrupt-linkage
High-level communications
2. An integrated high-level
protocol for down loading from
interactive language allows for
a host system.
fast software develoDment.
HARDWARE
Application programs are
stored automatically in non-
volatile memory.
The STD BUS interface allows
the use of a variety of existing
P~OPL~WRRE JYJTEMJ INC.
5190 west 76th St.
MplS., MN 55435 USA
peripheral cards. (612)831-0827 TWX 910-576-1735
FORTH Dimensions 14
6801 microprocessor
6K EEROM
8~ FORTH firmware
2K RAM
STD BUS interface
RS232 serial I/O
16 TTL I/O lines
Programmable timer
Volume IV. No. 4
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