The BELLFLOW flowcharting system was developed to meet certain Bell System standards of documentation. There are three modes of operation with the BELLFLOW system: source mode, comment mode, and mixed mode. In the source mode, all of the flowcharting information is derived directly from the source code. In the comment mode, BELLFLOW ignores the source code completely and derives the entire flowchart purely from comments imbedded in the program. In the mixed mode, the source and comment mode are combined. The mixed mode is unique to BELLFLOW and was designed to provide a self-documenting program source deck. Other features of BELLFLOW include: automatic placement, automatic line routing, paging, and generation of on and off sheet connectors

Pardee, S.

English

NASA Technical Reports Server

ATHE BELLFLOW SYSTEM
Stephen Pardee
Bell Telephone Laboratories
STANDARDS
One of the primary reasons for the development of BELLFLOW was the need to meet
certain Bell System standards of documentation. The Bell System has been documenting de-
signs for a long time and, in addition to trying to observe outside standards, has additional
internal standards that must be observed. In the area of flowcharting, most of these additional
standards relate to quality and not to symbol or line character size, legibility, titling infor-
mation, change information, information placement, and format. BELLFLOW had to be
able to meet these quality standards. The symbols incorporated in BELLFLOW are essen-
tially the standard flowcharting symbols. (See fig. 1 for a list of the BELLFLOW symbols.)
MANUAL
OPERATION
PUNCHED CARD
MANUAL INPUT
ON-LINE
STORAGE
DECISION
MAGNETIC
( ) TAPE
AUXILIARY
OPERATION
OFF-LINE
STORAGE
TERMINAL
PROCESSING
PUNCHED TAPE
DOCUMENT
INPUT/OUTPUT
DISPLAY
CONNECTOR
Figure 1.-Standard BELLFLOW symbols.
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34 AUTOMATED METHODS OF COMPUTER PROGRAM DOCUMENTATION
ADDITION OF NEW LANGUAGES
Another important reason for the development of BELLFLOW was the need to provide
a flowcharting system structure that would allow the addition of new or unique special lan-
guages. There are many people at Bell Laboratories developing one-time languages or special
languages that are unique to a very small area of design. These languages should be able to be
conveniently added to the BELLFLOW system. By making BELLFLOW a model or table-
driven system, a language has been developed that can be used for defining new programming
languages in terms of BELLFLOW. As an example, consider the standard IF statement:
IF A = B T H E I M C = D
In BELLFLOW language, this would be
.B.IF.B..T..B.THEN.B..S. /S(B*)
The following shows the entire set of model language statements required to define a
programming language that is very close to PL/I structurally but not quite as complicated:
.STATEMENTC';").
.LABEL(":").
.COMMENT!"/*").
.COMMENT!,"*/").
(.B.IF.B..T..B.THEN.B..S.) /S(*B)
(B.ELSE.B..S) /S(*L)
(.B.GObTO.B.J.) /S(*Z)
(.B.DO.E.=.E.) /S(*D)
(.B.DO.B.) /S(*G)
(.B.END.B.) /F(F1)
(.B.END.B..J.) /(*T)
F1 (.B.CALL.B) /S(*C)
(.B.RETURN.B.) /S(*Y)
(.B.EXIT.B.) /S(*S)F(*X)
This set of statements is not supposed to provide an understanding of the details of the lan-
guage itself but to show how straightforward it is to define a new programming language for
the BELLFLOW system. For example, a new language called CENTRAN was recently added
to BELLFLOW. It took about a week to develop the models, and, within another week or
two, the system was essentially debugged and ready for use by programmers writing in the
CENTRAN language.
USE OF GRAFPAC
Bell Laboratories uses a software package called GRAFPAC, which interfaces with all
of our graphical devices. At the present time, the GRAFPAC system supports such devices
as the SD 4060 and FR 80 microfilm plotters; the CALCOMP 718 and 728 and EAI 3500
line plotters; the Graphic 101 CRT terminal: STARE, an on-line hard-copy graphic unit that
THE BELLFLOW SYSTEM 35
possesses quick turnaround features; and several others. The flowcharting system is inter-
faced through GRAFPAC so that, as new graphical devices are brought into Bell Laboratories
and added to the GRAFPAC system, they are automatically available to the BELLFLOW
system.
MULTIPLE-LEVEL FLOWCHARTS
Multiple-level flowcharts (very-high-system-level and very-low-detail-level) should also
be imbeddable in the same source program. In addition, it is often desirable to imbed a sep-
arate flowchart for each procedure of a program even though all the procedures are compiled
as'a unit.
MODES OF OPERATIONS
There are three modes of operation: source mode, comment mode, and mixed mode.
In the source mode, all of the flowcharting information is derived directly from the source
code. This is similar to the way many other flowcharting systems operate. There is no reli-
ance on comments or other information in the derivation of the entire flowchart.
In the comment mode, BELLFLOW ignores the source code completely and derives
the entire flowchart purely from comments imbedded in the program. This has the advan-
tage of being able to imbed comments in any program, whether or not the source language
is supported by BELLFLOW. In the mixed mode, the source and comment mode are com-
bined. The text that is to appear within a symbol and the definition of the symbol to be
used are derived from a comment imbedded in the source code, but BELLFLOW uses the
source code itself to determine the connections among the symbols and the placement and
layout of the flowchart.
SELF-DOCUMENTING SOURCE DECK
Because the mixed mode is unique to BELLFLOW, it may be of interest to explore
the particular advantages of this mode. The goal was to try to provide a self-documenting
program source deck. To achieve self-documentation, the flowchart should be imbedded in
the source deck, and the source deck must be well commented. The question of what con-
stitutes a "well-commented" program is too difficult to bring up here. In any event, most
programmers use an intuitive definition of the term in deciding whether a program is well
commented. A brief program description should also be imbedded at the beginning of the
source deck. Given these three features, a subroutine or a program would contain most of
the information needed for program documentation.
If the program flowchart is based on the source code alone (using the source mode),
a very good two-dimensional representation and a poor functional description of the pro-
gram are obtained. Many people feel that FORTRAN and other languages, such as PL/I, can
be documented very nicely by placing the source code within the symbols, but this approach
does not seem very fruitful.
If the flowchart is based only on comments that are imbedded in the program (using
the comment mode), the result may be an excellent functional description of the program
36 AUTOMATED METHODS OF COMPUTER PROGRAM DOCUMENTATION
DO 10 I • 1, IEND
IF (JGET (12. I) .EQ. BUNKS) GO TO 11
ICOUNT • 1COUNT + 1
10 CONTINUE
11 IF (ICOUNT,EQ. Q) I C O U N T - 1
(a)
in understandable language, but no real tie-in
between those comments and the program itself.
It is not certain that the comments reflect the
flow and interconnectivity of the program.
Furthermore, the programmers usually have to
supply a lot of redundant information in the
comments to express the interconnectivity
among the symbols.
The mixed mode permits one to put text
inside symbols in a way that is meaningful to a
person trying to understand a program, and yet,
the fact that the program flow (the interconnec-
tivity among symbols) is derived from the source
code itself is still retained. No other comments
other than the BELLFLOW comments are re-
quired to produce a well-commented program.
If a preface is added at the beginning of the pro-
gram (a manual operation), a self-documenting
source program deck is obtained.
EXAMPLES OF BELLFLOW
Figure 2(a) is an example of the source
mode in FORTRAN. Figure 2(b) shows the cor-
responding flowchart that would be generated.
Quite often, the source mode is used when im-
provements have to be made in an old FORTRAN
program. Because it is not always possible to lo-
cate the original program writer, it is very con-
venient to be able to obtain a two-dimensional flowchart listing in the source mode; this
makes the task much easier than it would be if a linear listing of the program had to be used.
The comment mode format is
*F(LEVEL)(LABEL) TEXT /SYMBOL/OUTPUT
The comment begins with an indicator that is the normal comment indicator of the program-
ming language. For an assembly language, the indicator might be an asterisk in the first column.
The letter F indicates that a flowchart comment is being made. The next field is a level indi-
cator that allows one to imbed more than one set of flowchart comments; it is a two-
character identifier that denotes a particular flowchart. If there is only one flowchart im-
bedded in the program, this field may be left blank. The label field is usually left blank un-
less it is needed to specify interconnectivity.
The main body in this statement is the comment text field, which conveys the informa-
tion that is to appear in the symbol. The final two fields at the end of the statement are the
symbol field and the output field. The output field contains information that is to be placed
(b)
Figure 2.-(a) FORTRAN source mode,
(b) Corresponding flowchart.
THE BELLFLOW SYSTEM 37
*F
*F
*F WD
*F READ';
(a)
I:; I'lOOE i.;ET
HUNCH A CAKD CONTAINING 8S /iO/(REAIo)
PUNCH A CAKD CONTAINING 2C /iO
I N I T I A L I S E VAi< TABLES AN'O ARRAYS
PUNCH A
CARD
CONTAINING
8C
PUNCH A
CARD
CONTAINING
8S
(b)
Figure 3.-(a) Imbedded comments, (b) Typical comment mode flowchart.
on output branches emanating from symbols, and, in some cases, it specifies the interconnec-
tivity between one symbol and another.
An example of the comment mode format is
* F IS COUNT=MAX+TOL /D/YES,NO
Here, the level is blank, and there is no label. The letter D in the symbol field indicates a
decision symbol. One branch will have the label YES, and the other branch will have the
label NO. Figure 3 shows a typical portion of a comment mode flowchart.
The comment mode is extremely useful in preliminary design for the generation of
system flowcharts when no code exists or as part of the documentation of an early design.
A complicated flowchart can be quickly encoded, run off, modified, edited over a period
of meetings, and kept up to date by using the comment mode without ever having any
source code. The comment mode is also being used to generate nonprogramming documen-
tation such as flowchart-like and program evaluation and review technique drawings, and
input/output relation tables.
38 AUTOMATED METHODS OF COMPUTER PROGRAM DOCUMENTATION
Figure 4.—Correspondence of program
to flowchart.
Figure 4 is a flowchart consisting of
five symbols. The lines on the left are used
to indicate statements of source code and
are grouped to indicate which statements
correspond to the five symbols in the flow-
chart. In the mixed mode, a BELLFLOW
comment is inserted at the beginning of
each one of these functional groupings of
source code.
Figure 5(a) is an example of the mixed
mode. Note that the comments are very
similar to the ones that might be placed in
a program even if BELLFLOW were not be-
ing used. The second BELLFLOW comment,
"ARE SIGNS EQUAL," is the text for a
decision symbol with two branches labeled
YES and NO. There are two ways to exit
from this functional block. The first one is encountered at the skip instruction (SPA), and
the second one is encountered at the jump (IMP), so the YES text is associated with the
first way to exit and the NO text is associated with the second way to exit. Figure 5(b)
shows the corresponding flowchart. It is important to repeat at this point that the BELL-
FLOW comments are really all the comments that are needed to provide a well-commented
source deck.
BELLFLOW FEATURES
In addition to automatic placement, automatic line routing, paging, and generation of
on- and off-sheet connectors, all of which are standard regardless of the mode employed,
BELLFLOW possesses some additional features. One can request left-to-right rather than
top-to-bottom flow in the flowchart. Normally, BELLFLOW will automatically format the
text that goes in a symbol, but the programmer can do this himself if he considers it desirable.
BELLFLOW will adhere to standard aspect ratios in choosing symbol sizes but also has
the capability of using nonstandard symbol sizes. In the latter case, processing symbols (rec-
tangles, for example), are reduced to fit exactly around the text provided. It is interesting to
note that, in a brief study of this capability, a gain of almost 50 percent in the number of
symbols per vertical row was achieved with the use of the nonstandard symbol sizes. Increas-
ing the number of symbols per sheet reduces the number of off-sheet connectors and, there-
fore, simplifies the flow and makes it more readable.
BELLFLOW permits multiple keypunch codes to be used, and an option is provided
that permits flowcharts to be made without any crossovers. The normal mode will make
crossovers unless too many lines are crossed, in which case an on-sheet connector is
generated.
THE BELLFLOW SYSTEM 39
DAC F2
*
•F S:;:FT FRACTION- U2) RIGHT DE PLACES
*
SHIFT LAC !-•£
TAD ^H!?T1
DAC «+2
LAC F2
CSS 1
DAC F2
• F ARE SIGNS EQUAL / D / Y C S / N O
LAC FI
XOR F2
SPA
JMP UNEQ
•
• F ADD FI AND F2,SHIFT FOR f-OSSIBLE OVERFLY
*
CLL
(a)
SHIFT FRACTION (F2)
RIGHT DE PLACES
NO
ADD FI AND F2,
SHIFT FOR
POSSIBLE OVERFLOW TO SYMBOL CONTAINING
SOURCE LABEL = UNEQ
(b)
Figure S.-(a) Comments, (b) Flowchart for BELLFLOW mixed mode example.
SAMPLE OUTPUTS
Figure 6 is an example of the BELLFLOW output produced by the FR 80 microfilm
plotter. Note the placement, line routing, and general quality features of the flowchart. The
cost of such a flowchart sheet, including the analysis and drawing, is about $2 to $3 when
the IBM 360/85 is used.
Figure 7 is another example of the BELLFLOW output; this one was made by a
CALCOMP line plotter. It is larger than the sheet shown in Figure 6 and has about 50 sym-
bols. Again, the important things to note are the placement, line routing, and general quality
features of the flowchart. Figure 8 shows the same flowchart that Figure 7 does, but it was
made with left-to-right rather than vertical flow.
40 AUTOMATED METHODS OF COMPUTER PROGRAM DOCUMENTATION
Figure 6.—Sample FR 80 microfilm output.
Figure 7.-Sample CALCOMP output.
THE BELLFLOW SYSTEM 41
I '
Figure 8.-Sample CALCOMP output, left-to-right flow.
CONCLUSION
The BELLFLOW system has been working for about a year and a half. One project
manager, who heads a rather sizable software development project, stated that with BELL-
FLOW he felt that he had an adequate means for insuring that he had both a well-commented
and properly flowcharted program. He insists that programmers must deliver a flowchart,
in the mixed mode, to him before he will accept their program and consider it complete. By
following this procedure, he reasons that, if a good flowchart can be produced, then the
comments that appear in the deck are also understandable, meaningful, and useful. So he
accomplishes the dual goal of having a program well-commented and properly flowcharted
by using BELLFLOW as an administrative tool.
DISCUSSION
MEMBER OF THE AUDIENCE: In the event that the comments and the actual opera-
tion statements do not match, is there an editing function in the BELLFLOW system that
would point this out?
PARDEE: There is no specific function that points this out.
MEMBER OF THE AUDIENCE: I would like to ask the same question I asked Goetz:
Do you document BELLFLOW with BELLFLOW?
42 AUTOMATED METHODS OF COMPUTER PROGRAM DOCUMENTATION
PARDEE: Yes.
MEMBER OF THE AUDIENCE: If the syntax of the modal language is unambiguous
in the program mode, would it be possible to program from the flowcharts using the logic
to work back to a program? Also, is it possible to alter the placement, of things on flowcharts?
PARDEE: Programming from the flowchart is something that we are going to study.
We do not know enough yet to be able to say whether it might be helpful to input a flow-
chart and then have the machine automatically convert the logic into a source code. There
is a manual placement option that can exert a certain amount of control in the relative
placement of symbols, but it does not control specific placement. We are investigating the
possibility of a manual touchup capability that would be able to make specific changes in
the flowchart.
MEMBER OF THE AUDIENCE: Why was not any mention made of the IBM 360/67?
PARDEE: Our philosophy was to detach ourselves from the compiler and assembler
functions to remain somewhat independent of the machines and any changes involving com-
pilers and assemblers and to deal only basically with the language, which was fairly well
defined.
MEMBER OF THE AUDIENCE: Do you have any plans for making BELLFLOW a
commercial product?
PARDEE: No. There is the possibility of people having access to BELLFLOW, however.


The BELLFLOW system

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