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FORTH PROGRAMMING SYSTEM
DECSYSTEM-10 DOCUMENTATION FILE
28 NOVEMBER 1978
M. S. EWING, CALTECH
This File describes the second DECsystem-10 version of Forth
that has been submitted to DECUS. This document should be read
after the principle report: "The Caltech Forth Manual", Second
Edition, June, 1978, A Technical Report of the Owens VAlley Radio
Observatory, California Institute of Technology. (The 139-page
Manual is available from Bookstore, Caltech, Pasadena,
California 91125. The price is $6.00 including postage, handling,
and applicable taxes.)
This version is a substantial update of the original DECUS distri-
bution. The Forth address interpreter has been improved so that NEXT
consists of only a single machine instruction. There are also
only 2 words required in each word header since the code address field
has been eliminated. These improvements correspond to the changes
made in PDP-11 Forth, which also has been resubmitted to DECUS.
The following files are included in the new distribution:
FORTH.MAC MACRO-10 Source File
FORSYS.DAT Forth "system" file (block i/o)
FORTH.DOC This document
FDUM.MAC A dummy Macro program to help link in Fortran
FORTH.COM A sample command file to assemble, link,
and run Forth
You may choose between several assembly options:
..FORT Causes certain externals to be defined which correspond
to routines in the DEC-10 Fortran library. These are
SIN., COS., SQRT., ATAN., ATAN2., EXP., IFX.2, ASIN.,
CEXP., FLT.2, ALG10., and ALOG. You may add others as
TWSEG Causes a two-segment program to be assembled, with
sharable and reentrant code in the high segment. If not
defined a standard one-segment program results.
The one-segment version generally uses a bit less total
KORE Selects the number of kilowords of initial dictionary
space to be reserved. The Forth word CORE may be used
to alter the allocation at run time.
This section deals with peculiarities of the DEC-10 Forth
particularly as compared with the "standard" vocabulary of the
FPMATH Say FPMATH LOAD to obtain the assembler for
the KA-10 model of the DECsystem-10. (Single precision only).
Also loaded are the following words which call the indicated Fortran
routines. (Note that the ..FORT option must have been specified
in the assembly.)
Forth function "Fortran" expression
----- -------- --------------------
SQRT Square root. X --> SQRT(X)
FIX Fix a floating number. X --> IFIX(X)
FLOAT Float an integer. I --> FLOAT(I)
LOG10 Log base 10. X --> ALOG10(X)
LOG Log base e. X --> ALOG(X)
EXP Exponential X --> EXP(X)
SIN Sine X --> SIN(X)
COS Cosine X --> COS(X)
ATAN Arctangent X --> ATAN(X)
ATAN2 Arctangent of quotient X Y --> ATAN2(X,Y)
CEXP Complex exponential X Y --> CEXP( X + iY)
These functions are implemented as machine language calls to
the Fortran library routines. They are vectored through the
FORTRAN table in the kernel which is loaded with the run time
addresses of the routines.
SLEEP Puts the program to sleep for the number of seconds specified
via the stack.
ILDB Given the address of a byte pointer on the stack, ILDB increments
the byte pointer, fetches that byte, and returns the byte on
the stack. (Mimics the ILDB machine instruction.)
IBP Given a byte pointer address on stack, increment byte pointer by
VIBP Variable IBP. Say <byte pointer address> <byte increment> VIBP.
This adjusts the byte pointer by the increment. The increment
may have any reasonable integer value.
<R Equivalent to >R in standard vocabulary.
<: Equivalent to >: in standard vocabulary.
BYTE-POINTER Like CONSTANT but defines a DEC-10 byte pointer.
Say i j k BYTE-POINTER <name> to define <name> as a pointer with
address i, j bits per byte, and bit offset k. If k=36(10),
the pointer is the first (leftmost) byte in the
FBYTE A constant which when added to an address gives a byte pointer to
the first 7-bit byte at that address.
SIXBIT Say SIXBIT <name> to get the sixbit equivalent of <name> on the
stack. Up to 6 characters in <name> are converted into a
36 bit integer.
XWD Combines two stack values into 18-bit fields of a single
36-bit integer. Say <left half> <right half> XWD.
FFTPACKAGE This is a sample application vocabulary. It is a set of
routines that computes the fast Fourier transform of DIM =
2 ** LOGDIM complex floating point data points. Load data into
DATA array (using !C) and say FORWARD FFT to compute the FFT.
REVERSE FFT should restore the original data. Each operation
results in a scaling upward by a factor DIM, no normalization
The entire Forth vocabulary is defined in upper case characters.
Lower case characters are understood, but are distinguished
from upper case. We suggest you use .SET TTY NO LC.