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IBM 1620 User Manual

IBM 1620
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Floating Point
Accumulator
Subroutine
Linkage
Error
Analysis
of
Subroutines
The
preceding
table
shows
each
subroutine provided, its type,
the
num-
ber
of operands
it
requires,
and
its symbolic name.
The
symbolic names shown
on this
table
are
not
used
in
programming;
they
are
included
to
provide
refer-
ence
to
the
symbolic listing of
the
subroutines.
The
results of all floating
point
subroutines
appear
in a 10-digit field
which
ex-
tends from storage positions
00051
through
00060. This field is called
the
floating
point
accumulator
(FAC).
The
symbol,
FAC,
is associated with
the
address 00060
in
the
symbolic listing of
the
system.
F
AC
is also
used
as
the
fixed point accumulator. Fixed
point
numbers
occupy
only
the
four low-order positions of
FAC,
00057-00060.
The
subroutine linkage is in
the
form
BTM
SUBR A
(where
A is
the
address of
the
argument)
for arithmetic subroutines.
The
number
stored in
FAC
is
added
to,
subtracted
from,
divided
by, or multiplied
by
the
operand.
Both
type
2
and
type 3 subroutines
are
relocatable
and
are
loaded
only
if
called for.
Toward
the
beginning of
the
compilation phase,
the
symbol
table
area
is
cleared.
The
symbolic
name
of
the
subroutine,
SIN,
is
loaded
into a specific
10-digit field in
the
symbol table.
The
address of this field is
derived
from
the
order
in
which
the
subroutine names
are
listed in
the
FORTRAN
processor.
The
symbol is left-justified in
the
field,
and
the
high-order address of
that
field is
associated
with
the
function subroutine.
The
10-digit field immediately
preceding
this field is also associated
with
the
same function subroutine.
For
example,
if
the
subroutine
order
is
the
order
used
by
IBM
Programming Systems in
the
decks
they
prepare
and
release,
the
locations 19990
through
19999
are
reserved for
the
symbol
SIN
and
the
preceding ten digits, 19980 through 19989,
are
also reserved
for
the
sine subroutine.
If
the
program calls for
the
sine subroutine (i.e.,
the
sine
function is
used
in
an arithmetic
statement),
the
following instruction is compiled:
BTM
19990 , A
where
A is
the
address of
the
subroutine argument.
When
the
subroutine has
been
assigned
an
absolute address,
the
symbol
SIN
is
replaced
by
49
xxxxx,
where
xxxxx
is
the
absolute address of the
FSIN
subroutine in memory. Thus,
when
the
BTM
19990 A instruction is executed in
the
object program,
the
address of
the
argument
will
be
transmitted to 19985
through
19989,
and
the
branch
to 19990
will
be
followed
by
a
branch
to the
FSIN
subroutine.
Results of all
FORTRAN
subroutines
are
truncated
(except
FMP
and
FEXP,
where
the
result is
rounded),
and,
in
general, errors
are
no
greater
than
one
in
the
last digit
of
the
resulting mantissa.
The
exceptions to this
statement
are
listed
below:
FLN:
The
argument
of
the
FLN
subroutine is broken into an integral
and
a frac-
tional
part.
The
logarithm of
the
fraction is evaluated using a series expansion.
The
result is correct to nine decimal digits.
The
integral
part
of
the
argument
is
multiplied
by
Inl0
and
added
to
the
above result
to
produce
the
desired value.
For
values of
the
argument
in
the
range
.99<ARG
.::::;
1.01, some loss of accuracy
will occur.
The
reason for this is
that
some of
the
digits calculated will
be
leading
zeros, and,
when
the
result is normalized, fewer
than
eight
significant digits will
remain.
FEXP:
The
antilogarithm is
computed
using a Hastings'
approximation~
for
lOX.
The
argument
is initially multiplied
by
log e
and
then
divided
into
an
integral
«Hastings, Cecil, Jr., Approximations for Digital Computers,
Princeton University Press, New Jersey,
The
Rand
Corporation, 1955
Analysis of the
FORTRAN
Program 59

Table of Contents

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IBM 1620 Specifications

General IconGeneral
CategoryDesktop
ManufacturerIBM
Model1620
Introduced1959
WeightApproximately 1, 000 pounds
Memory20, 000 to 60, 000 digits
ProgrammingFORTRAN, Symbolic Programming System (SPS)
CPUDecimal, variable word length
StorageMagnetic disk drive (IBM 1311)

Summary

Introduction to IBM FORTRAN

Writing the 1620 FORTRAN Program

Floating Point Arithmetic Explained

Details floating point arithmetic, mantissa, and exponent representation.

FORTRAN Constants: Definition and Types

Defines constants and explains fixed and floating point constant formats.

FORTRAN Variables: Definition and Naming

Explains variables, their distinction from constants, and naming conventions.

FORTRAN Subscripts and Arrays

Explains subscripts for referencing array elements and defining arrays.

Arithmetic Statements

Describes how numerical calculations are defined using arithmetic statements.

FORTRAN Expressions: Structure and Operations

Defines expressions and lists the basic FORTRAN operation symbols.

Control Statements

Explains control statements that provide flexibility in program development.

Unconditional GO TO Statement

Describes the unconditional GO TO statement for transferring program execution.

Computed GO TO Statement

Explains the computed GO TO statement for conditional transfers.

IF Statement for Conditional Logic

Details the IF statement for transferring program flow based on expression values.

DO Statement for Looping Constructs

Explains the DO statement for simplifying loop programming and providing flexibility.

Nested DO Statements and Rules

Explains the rules for nesting DO statements within other DO statements.

Input/Output Statements

Explains statements used to read data into programs and output results.

READ Statement for Card Input

Details the READ statement for inputting data from punched cards.

ACCEPT Statement for Typewriter Input

ACCEPT TAPE Statement for Paper Tape Input

PUNCH Statement for Card Output

TYPE Statement for Typewriter Output

PRINT Statement for Printer Output

Explains the PRINT statement for outputting data to the 1443 Printer.

PUNCH TAPE Statement for Paper Tape Output

FORTRAN Specification Statements

Introduces specification statements, including FORMAT and DIMENSION.

FORMAT Statement for Data Conversion

Explains the FORMAT statement for controlling input/output data conversion.

FORMAT Statement Output Specifications

Explains I (Integer) and F (Floating Point) conversion for output.

Specifying Alphameric Fields in FORMAT

DIMENSION Statement

Explains the DIMENSION statement for allocating storage for arrays.

Writing FORTRAN Statements for Problem Solution

Processing with the FORTRAN Pre-Compiler

Operating Principles

Producing the Object Program

Explains the fundamental steps for creating the object program from source code.

Clearing Core Storage to Zero

Console Switch Settings for Compilation

Loading the FORTRAN Compiler

Explains the procedures for loading the compiler program deck or tape.

Compiling the FORTRAN Source Program

Describes how to initiate compilation of the FORTRAN source program.

Loading FORTRAN Subroutines

Explains how to load subroutine decks or tapes after source program compilation.

Common Source Program Errors During Compilation

Executing the Object Program

Details the procedures for loading and executing the compiled FORTRAN object program.

Inputting Data from the Keyboard During Execution

Using the Trace Feature for Debugging

Explains how to use the trace feature to monitor program flow and check correctness.

Analysis of the FORTRAN Program

FORTRAN Subroutines: Overview and Classification

Introduces FORTRAN subroutines, their types, and available sets.

Floating Point Accumulator (FAC)

FORTRAN Subroutine Linkage Mechanism

Error Analysis of FORTRAN Subroutines

Discusses errors, their codes, and FAC values for FORTRAN subroutines.

FORTRAN Subroutine Error Checks and Codes

Lists subroutine error checks, error codes, and FAC values for error conditions.

Adding Custom Subroutines to FORTRAN

Processor

Processor Subroutine Management

Storage Allocation

Storage Allocation After Compiler Loading

Storage Allocation After Source Program Processing

The FORTRAN Pre-Compiler Program

Operation of the FORTRAN Pre-Compiler

Explains the two-phase operation: Error Analysis and Final Program Summary.

Pre-Compiler Error Code Categories

Categorizes the common errors detected by the Pre-Compiler program.

FORTRAN Statement Number Errors

FORTRAN Transfer Statement Errors

General FORTRAN Statement Errors

Error Analysis Phase

Restart Procedures in Error Analysis

Final Program Summary in Pre-Compiler

Program Switch Settings

Loading the FORTRAN Pre-Compiler Program

Details the steps required to load the FORTRAN Pre-Compiler program.

Processing the Source Program with Pre-Compiler

Explains how to process the source program using the Pre-Compiler.

Pre-Compiler Program Deck Structure

Pre-Compiler Program Tape Structure

Pre-Compiler Tape Data Identification

Duplicating the FORTRAN Pre-Compiler Tape

Appendix A - Summary of 1620 FORTRAN Statements

ACCEPT Statement Summary

ACCEPT TAPE Statement Summary

DIMENSION Statement Summary

Summarizes the DIMENSION statement for array declaration.

DO Statement Summary

Summarizes the DO statement for loop control.

FORMAT Statement Summary

Summarizes the FORMAT statement for data conversion.

GO TO Statement Summary

Computed GO TO Statement Summary

IF Statement Summary

Summarizes the IF statement for conditional logic.

PRINT Statement Summary

Summarizes the PRINT statement for printer output.

PUNCH Statement Summary

PUNCH TAPE Statement Summary

READ Statement Summary

Summarizes the READ statement for card input.

TYPE Statement Summary

Summary of 1620 Operating Principles

1620 Typewriter Input Operations

Manual Data Entry via Typewriter

Typewriter Output Operations

Paper Tape Input Procedures

IBM Tape Punch Operation

IBM 1621 Paper Tape Reader Operation

Card Input

Covers the process of inputting data via punched cards.

IBM 1622 Card Read Punch Overview

Provides an overview of the IBM 1622 Card Read Punch.

1622 Card Feed Motor Control

1622 Card Read Operation

1622 Card Punch Operation

1622 Operator Keys and Lights

1622 Card Reader Controls and Indicators

1622 Card Punch Controls and Indicators

IBM 1443 Printer Overview

Provides an overview of the IBM 1443 printer.

1443 Printer Keys, Lights, and Switches

Details the keys, lights, and switches for operating the 1443 printer.

1443 Printer Start Key Operation

Explains the operation of the 1443 printer's start key.

1443 Printer Stop Key Operation

Details the operation of the 1443 printer's stop key.

1443 Printer Power On Light

1443 Printer Ready Light

Explains the function of the 1443 printer's ready light.

1443 Printer Sync Check Light

Describes the 1443 printer's sync check light and error conditions.

1443 Printer Parity Check Light

Explains the 1443 printer's parity check light indicator.

1443 Printer Form Check Light

1443 Printer End-of-Form Light

1443 Printer Manual Controls

Details the manual controls for operating the 1443 printer.

1443 Character-Set Selection Switch

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