EasyManuals Logo

IBM 7090 User Manual

IBM 7090
190 pages
To Next Page IconTo Next Page
To Next Page IconTo Next Page
To Previous Page IconTo Previous Page
To Previous Page IconTo Previous Page
Page #69 background imageLoading...
Page #69 background image
count
of
438
will
give
the
same
result
as
DVH. A
count
greater
than
438
causes
part
of
the
quotient
to
be
shifted
into
the
AC,
where
it
can
be
altered.
A
count
of
60S
or
greater
will
cause
an
I/A
cycle,
and
the
count
field
(12-17)
will
OR
with
12-17
of
the
IA
word.
Variable-Length
Divide
or
Proceed
VDP
+0225 (Min
I,
E)
Figure
5.3-20
Max
I,
E,
12L)
The
execution
of
this
instruction
is
the
same
as
VDH,
except
that
the
computer
will
not
stop
for
a
divide
check,
but
will
proceed
to
the
next
instruction.
Round
RND
+0760
...
0010
(I,
L)
Figure
5.3-21
This
instruction
examines
the
contents
of
MQ(l)
and
if
it
contains
a
one,
the
magni-
tude
of
the
AC
is
increased
by
one.
If
MQ(l)
contains
a
zero,
the
AC
is
unchanged.
The
MQ
is
not
changed
in
either
case.
AC
overflow
is
possible.
This
is
a
primary
opera-
tion
76
instruction.
The
contents
of
the
AC
are
sent
to
the
AD
and,
if
MQ(l)
contains
a
one,
a one
is
sent
to
AD(35)
and
the
output
of
the
AD
replaces
the
contents
of
the
AC.
Clear
Magnitude
CLM
+0760
...
0000
(I,
L)
Figure
5.3-22
This
instruction
puts
zeros
in
AC(Q-35).
CLM
is
a
primary
operation
76
instruction.
The
operation
is
accomplished
by
gating
the
AD
to
the
AC,
with
nothing
in
the
adders.
The
AC(S)
remains
unchanged.
Complement
Magnitude
COM +0760
...
0006
(I,
L)
Figure
5.3-22
The
contents
of
the
AC(Q-35)
are
complemented.
Positions
containing
ones
are
changed
to
zeros
and
positions
containing
zeros
are
changed
to
ones.
This
instruction
is
executed
by
complementing
the
AC
to
the
AD
and
replacing
the
contents
of
the
AC
with
this
complement.
5.3.04
Floating-Point
Arithmetic
Instructions
The
range
of
numbers
anticipated
during
a
calculation
may
be
extremely
large,
extremely
small
or,
in
some
cases,
unpredictable.
Such
situations
make
fixed-point
arithmetic
difficult
to
work
with
for
two
reasons;
1.
The
size
of
the
number
is
limited
by
the
size
of
the
register
(35
binary
bits
or
10
decimal
digits).
2.
The
programmer
must
keep
track
of
the
point
in
all
numbers
throughout
the
calculation.
To
meet
the
needs
of
large
numbers
and
to
automatically
keep
track
of
the
point,
an
alternative
set
of
arithmetic
instructions,
called
floating-point
arithmetic
instructions,
are
available.
Floating-point
arithmetic
is
merely
arithmetic
dealing
with
numbers
in
exponential
form.
The
numbers
5.6
x 10
3
or
56000 x
10-
4
have
a
familiar
form.
The
numbers
are
made
of
three
parts;
a
fraction
(5.6
or
56000),
an
exponent
(3
or
-4),
and
a
base
(10).
Floating-point
numbers
in
binary
are
similar
to
decimal
floating-point
numbers.
The
major
difference
is
the
base.
Numbers
in
the
7090
use
2
as
a
base,
because
it
is
a
binary
computer.
The
other
difference
is
one of
terms.
Instead
of
a
decimal
point,
we
will
call
it
a
binary
point.
The
following
chart
gives
a
comparison
of
fixed-point
binary
numbers
and
floating-
point
binary.
68

Table of Contents

Questions and Answers:

Question and Answer IconNeed help?

Do you have a question about the IBM 7090 and is the answer not in the manual?

IBM 7090 Specifications

General IconGeneral
CategoryMainframe Computer
Introduced1959
Transistor-basedYes
Word Length36 bits
Add Time4.8 microseconds
MemoryCore memory
Memory (words)32, 768 words