IBM 1620 User Manual

Executing the Object
Program
Program Testing
Program Verification
3. After the source statements have been compiled, the programmer or
operator can have the symbol table typed or printed.
4. A symbol table can contain the names of the subroutines used in this
processor; it can also contain storage area for constants and variables,
variable arrays, temporary accumulators, and statement numbers. (This
subject is covered in more detail in Part 4, ANALYSIS OF THE FORTRAN
PROGRAM.)
5. In this program, the object program was processed immediately following
its compilation,
therefore the subroutines were not punched as part of
the object program, but instead, were loaded into the 1620 after the object
program was loaded.
6. "Processing complete" means the object program has been compiled.
The illustration shows the information that results when the object program
is processed with data for various values of x, and A, B, C, and D have the
values of 10.0, 11.0, 12.0, and 13.0 respectively.
Typewriter Message
(j) ENTER SUBROUTINES, PUSH START
1620 FORTRAN PRNTR SUBR SET 2 11/63
LOAD DATA
CD
Printer Output
9.0000U
921.000UO
10.0000U
lln.ooooo
15.UOOOO
-2097.00000
25.00000
-5987.00000
5.00000
317.00000
7. The subroutines are read into storage, and the message "Load Data"
is typed.
8. The data is loaded. Five values of x are shown with their corresponding
values of f( x).
After you have written your program, you should thoroughly "desk check" it.
Desk checking is the process of looking over the source program for obvious
mistakes in logic or form, and the actual manual run of an item of data through
the program. This technique will quite often turn up a surprising number of
errors
in a new program.
After you have desk checked your program, you should prepare test data
that can be processed on your program. The test data should be accompanied
by the correct results so that they can be compared by the machine operator to
the results obtained when your program is tested.
You
should devote enough time for a careful selection of test data which
will check out the various and numerous combinations that may exist in the
logical flow of your program. It is advisable to start out with items of data which
will produce the simplest logical flow through your program and then to follow
with items of data which will take increaSingly more complex paths, so that each
new item will involve the use of a new subroutine or segment. The more care-
ful your data selection is, the less chance there will be of errors in actual data
results.
When your object program is processed with the test data, and the results indi-
cate that there is an error in the program, you can do several things to locate the
difficulty.
Writing the 1620 FORTRAN Program 49

IBM 1620 Specifications

General

Brand	IBM
Model	1620
Category	Desktop
Language	English