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Document:	DEC-06-UP-DESK-UM-FP-ACT01 Desk Calculator Programming Manual
Order Number:	XX-A1674-60
Revision:
Pages:	10
Original Filename:	http://bitsavers.org/pdf/dec/pdp6/DEC-06-UP-DESK-UM-FP-ACT01_Desk_Calculator_Programming_Manual_Oct65.pdf

OCR Text

DEC-06-UP-DESK-UM-FP-ACTOI

DIGITAL EQUIPMENT CORPORATION

•

MAYNARD, MASSACHUSETTS

DEC-06-UP-DESK-UM-FP-ACTOI

PDP- 6

PROGRAMMING MANUAL
DESK CALCULATOR

DIGITAL EQUIPMENT CORPORATION

•

MAYNARD, MASSACHUSETTS

INTRODUCTION
The Desk Calculator program improves man-machine communication by giving the computer user direct
access to basic mathematical functions within the PDP-6 subroutine library.

By means of the PDP-6 multi-

user station, the operator is able to enter arguments, request specific functions, and obtain resultants at
electronic speeds. No complex programming rules need be learned, and no involved operational procedures need be followed.

Some familiarity with modern programming systems is helpful, however, to

real ize the full range of capabil ities inherent in Desk Calculator.
The Desk Calculator program also incorporates the macro operations programming aid.

By the use of macro

operations, functions not contained in the normal repertoire can be represented by a single mnemonic symbol. The macro feature also includes conditional branching capabil ities, so that subroutines requiring
testing and decision-making can be implemented.

OPERATING INFORMATION
The Desk Calculator program is brought from the system tape, stored in memory, and initial ized by the
following control statements, typed on the teletypewriter:
IJOB
(Message)
CORE 2
GET SYS DESK
(Message)
START
where the number 2 represents the core memory space requ ired by the 2, OOO-word program. The number
of significant figures required may be set by a statement of the following form:
$FN
where N is any number between a and 7.
For example, to obtain the sine in radians of n/4 to five significant figures, the following is typed:
$F5
SIN(3.14159/4)~

The ~ character is a demand for output. The ALT MODE key is depressed to complete the input command. The program evaluates the typed expression and types the answer I so that the second I ine becomes

PDP

II BRARY

SIN(3.14159/4)~ 0.70711

Alternatively, the carriage return function could have been selected to complete the input command.
When this is done, the resultant appears on the next line.
Other functions of integers can be obtained in a similar way. Table 1 is a list of all functions contained
in the basic Desk Calculator program. Following is a Iist of the available arithmetic operators:
Operation

Symbol

add
subtract

multiply

divide
raise to the power

()

subexpression grouping parentheses
Replacement operator. The expression
on the left is stored into the variable
on the right. Multiple replacements may
be accompl ished by commands of the form
(exp) = a,b,c,

TABLE 1

LIST OF FUNCTIONS

Function

Description

ATN

arctangent in radians

COS

cosine in radians

CSD

cosine in degrees

EXP

exponential (ex)

LOG
SIN

natural logrithm (LOG X)
e
sine in radians

SND

sine in degrees

XNT

integer part (i.e., truncate floating-point number so
that only a floating-point integer remains)

PDP

LIBRARY

Pseudo- Operat ions
Pseudo-operations direct the program to perform certain util ity functions, and are so-called because of
their functional similarity to basic machine-language operations. Pseudo-operations provide for defining
macro-operations, deletion of resultants and functions, and output format specification.
A conceptual accumulator register is used that serves a purpose analogous to the hardware accumulator
register; that is, resultants are placed in the conceptual accumulator for reference or modification by
sub-sequent operations. Hence, a clear-accumulator pseudo-operation ($C) has been included to provide
for disposing of unneeded resultants.
Single-precision, floating-point arithmetic is used. By means of the $FN pseudo-operation, up to 7-place
accuracy can be specified. However, the propagation of round-off errors caused by nesting and similar
iterative procedures may in some cases cause a loss of significance in the seventh place.
Pseudo-operations are Iisted in Table 2. Note that pseudo-operations always begin with the $ symbol.

TABLE 2

PSEUDO-OPERATIONS

Symbol

Operation

Clear the accumulator

Define macro operation

$FN

Round output to N significant figures (0.:sN.:?)

Round output to nearest integer (same as $FO)

Delete the function specified by the user. If no
function is specified, delete all user functions, and
set all variables to 1.0.

Output line (carriage-return followed by a line-feed).
Used in macro operations.

Secondary exit from a macro-operation.

Output tab. Used in macro operations.

Variables
Variables are represented by a single letter (A-Z). Strictly speaking, variables represent memory locations,
the contents of which may vary.

FDF

LIBRARY

Comments
Comments are delineated by quotation marks (" "). Everything between the quotes is regarded by the
program as a comment.

Macro Operations
Macro operations or "macros" enable the programmer to generate useful extensions to the normal symbolic
repertoire of Desk Calculator. Macros are defined by the $D pseudo-operation. The i character de lim its
both the macro mnemonic and the instructions comprising the macro-operation. Hence, macros are generated by instructions of the form
$DMNEiINSi
where MNE is the macro name or mnemonic, and INS represents the series of instructions within the macro.
As an example, suppose we wish to obtain a macro that will furnish several functions of a variable, X.
We type the following statements to define the required macro:
$DLOP;
X ~ SND(X)!CSD(X)! SND(X)t2+CSD(X)t2~i
The ~ character causes the PDP-6 to output the expression value, followed by a tab.

The~ character

causes output of the expression value, followed by a carriage return. The accumulator is deared after
either operation. The program makes a normal exit at the end of the macro.
The macro can now be called by
LOP
and the program will respond by typing the values X, SIN X, COS X, and (SIN 2 X + C052 X).

Labels Within a Macro - Labels for symbolic memory locations are one to three digits in length, and must
be followed by a colon. Labels must be the first entry on a line.

Formatting - Formatting ot the macro operation output is accomplished by the! and ~ characters described above, and by the pseudo-operation's $L, $T, $FN, and $1, described in Table 2. Text may be
output by enclosing the character string within quotation marks.

PDP
4

1I BRARY

Arguments Within a Macro - Macros may contain up to nine arguments. Thus, calling statements will be
of the general form

where MNE is the macro mnemonic, A1 ... AN are the input arguments, and N <9. Within the macro
eac h argument is referenced by the expression # N (1:: N :: 9).

Transfers Within a Macro - Several conditional transfer instructions (Table 3) are available to facilitate
coding of functions and subroutines.

Except for the TA and STP instructions, the first argument of a con-

ditional transfer instruction is an expression, and the second is a label.
quired is a label.

For TA, the only argument re-

For STP, the first argument is a variable, and the second is a label.

An example of a macro using a conditional transfer is as follows:
$DABS;TGE(#1, 1 )$C-#1 $R
1 :#1;
In the macro above, ABS is defined as a transfer to label 1 if the first input argument of ABS is greater
than or equal to zero (TGE instruction).

If the transfer is made, the first argument is loaded into the

accumulator and a normal exit from the macro is made.

If no transfer is made, the accumulator is cleared,

the first argument is complemented, and an alternate exit is selected.

TABLE 3

TRANSFER INSTRUCTIONS

Mnemonic

Description

Transfer uncond i tiona I

Transfer if not zero

Transfer if equal to zero

Transfer if greater than zero

TGE

Transfer if greater than or equal to zero

Transfer if less than zero

TLE

Transfer if less than or equal to zero

STP

Subtract one from first argument, and transfer if the
resultant is greater than zero

PDP

II BRARY

Among the uses of macro operations is the generation of tabular lists of functions.

Suppose, for example,

we wish to generate a table of sines and cosines. The general form of the calling statement would be
SYM(I, T, S)
where I is the initial value of the argument for which trigonometric functions are to be generated, T is
the terminal value, and S is the amount by which the argument is increased before each successive pair
of functions is generated. This type of calling statement may be implemented by the following macro
operation (the Iines are numbered for reference):
Line No.

$DSYM

"X SINX COSX $L

3.
4.

#2=Y

1 :$F1 X: $F5SND(X) ~ CSD(X) ~

X+#3=X

TGE(Y-X,l)$Li

The macro name is set in line one, and tabular heading data is generated in line two.

In lines three and

four, the first two input arguments are assigned the symbolic designations X and Y. The fifth line prints
the argument X with one-place accuracy, and generates and prints the sine and cosine of X with fiveplace accuracy.
The sixth I ine increments the symbol ic argument X by the value of the third input argument; the resultant
sum becomes the new argument. The seventh line effects a transfer to line 5 to compute functions for the
new argument. When X equals or exceeds Y, line 7 effects a normal exit from the macro.
Suppose that the above macro has been coded. Typing the following statement,
TAB(l 0,60, 10)
followed by a carriage return, causes the program to generate the following printout:
X
10.0
20.0
30.0
40.0
50.0
60.0

SIN(X)
0.17365
0.34202
0.50000
0.64279
0.76604
0.86603

COS(X)
0.98481
0.93969
0.86603
0.76604
0.64279
0.50000

PDP

LI BRARY

Change Notice 1
PDP-6 Desk Calculator Programming
Manual
DEC-06-UP-DESK-UM-FP-ACT 01

To further increase the flexibility of the Desk
Calculator, the following features have been added:
1.

(single quote) will cause the accumulator
to be output, with no tab or carriage return
following.

$P,$G - PUT-GET - Save and restore variables
on the pushdown list. The form is:

$PX,Y,Z
$GZ,Y,X
Note that the list in the GET is reversed from
that in PUT. The arguments of PUT and GET must
be variables - not expressions. There is provision
for storage of 20 variables on the list.
3.

On page 6 in the manual, in the first chart, opposite
Line No.2: change "X SINXCOSX$L to read
"X
SIN (X)
COS (X)

mamaomo

EQUIPMENT
CORPORATION

MAYNARD,MASSACHUSETTS
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5516

PRINTED IN U.S.A.

5-10/65