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INFORMATION March 24, 1964
ElC-CHAN(jE 74 pages



David A. Barrett
Associate .Systems Engineer
IBM Israel Ltd.
15, Lincoln Street
; Tel-Aviv, Israel


This paper is in the author's original form.
The objective in providing this copy is to
. keep you informed in your field of interest.
Please do not distribute this paper to persons
oqtside the Company.

Distributed by
DPD Program Information Department
,IBM Corporation
112 East Post Road
White PI,ains, New York TIE 4-0064

Introduction 2

Section I 4
Add 4
Zero-Add 6
Subtract 7
Zero-Subtract 8
Unconditional ':Branch 9
Branch if Indicator on 10

Branch if character equal 11

Branch if word~arkor zone 12

No Operation 14
Compare 15
H8l.t 21

Clear Storage 22

Set & Clear Word~ark 23
Move 24
Move with zero suppressi~n 25
Move numeric, move zone 26
Load 27
Ed. it 28
Head, :Punch, Print 29
MultipJ.y 31

Section I (continued)
Divide 33
Modify Address 35
Store A-, B- address ;6
Section II 42
Address Modification and XRs 42
Subroutines 46
Magnetic Tapes 6;
Tables, Table hook-up 66
Diagrams 70
Fig. 1 70
Fig. 2 71
Abstract of Pa~

Basic Coding Tec~niques tor the IBM 1401 Computer.

David A. Barreiit

26th February l.964

Direct Inquiries to : David A. Barrett,
I:eM (Israe~) Ltd.,
15, Lincoln st.,
Tel-Aviv 31241

This paper is designed as an educational aid to progra..'l1n~ers

-beginning to work on the IB~ 1401 computer, and it also includes an
analysis of more .advanced techniques of program coding which may be
of interest to more experienced programmers. It is divided into two
. . sections,. the first of which analyses the use of the 1401 instructioh~,

,the second o~ which describez various 140J' programming techniques.
It could be used as a supplement to the 1401 machine manual.
Basic Coding Techniques for the 1401 Computer

It is not always advisable to Jr:estrict programmers to
simple techniques. A short-term advantage may be gained, in
that inexperienced personnel will make fewer mistakes. They
will tend not to over-rea~h themselves.

However, the 1401 computer offers a large number
of alternative methods of carrying out any particular operation.
In different circumstances, anyone of these methods may turn
out to be the most efficient solution, either because it uses up
less of the core storage, or because it will be executed faster.
When a programmer is able to condense a sequence of instructions
into a very small seetion of core storage, he is making room
for extra instructions and is effectively expanding the power of
his machine. In the same way, time-saving techniques increase
the effective speed of the machine. Such additions to the power
and speed of the 1401 can be quit~ significant.

Tight programming will also have a very be"neficial
effect on the morale of the installation which employs it.
Programmers gain a thorough understanding of their computer,
and make fewer mistakes in the simpler types of operation.
They also find themselves confronted with the problem of not
only making a program work. but of making it work efficiently .
This makes every program intrinsically more interesting, and
adds "to the concen~ration which they can bring to its solution.

Programmers should accustom themselves to the use
of storage -- or time-saving techniques as often as possible, so that
they may be entirely familiar with them when the need arises.

The potential IBM customer is advised to select
a team of trainee programmers, on the basis of various aptitude
and intelligence tests. These trainees are subjected to intensive.
IBM courses. Those who achieve high ratings on the course are
retaif:led as programmers by the customer, and are expected
to begin writing actual programs for their installation immediately.
Subsequent additions to the programming staff undergo a similar
training. but benefit to a real if small degree from the adv.ice of
their by now more experienced colleagues. Naturally the
customer requires that his installation be operation~l as soon
as possible, and the programmer training is designed with this