Ibm 3270 Manual

Systems

GA27-2742-1

Operator's Guide for

IBM

3270

Information

Display Systems

i i

Second Edition (July, 1972)

This

is

a major revision

of

GA27-2742-0 and incorporates Technical

Newsletter GN31-3001. Operating instructions for

the

printer and operator

identification card reader have been added. Comments and corrections have

been incorporated

throughout

the

manual.

Any system changes affecting this publication will

be

reported

in

subsequent

revisions

or

Technical Newsletters. Additional copies

of

this manual can be

obtained through

IBM

branch offices.

Text

for this publication has been prepared with

the

IBM

SE LECTR

IC

® Composer.

A form

is

provided

at

the

back

of

this publication

for

reader's comments. If

the

form

has been removed, comments may be addressed

to:

IBM

Systems Development Division,

Product Publications, Dept. 520, Neighborhood Road, Kingston, N.V., 12401

Contents

iii

Table

of

Contents

First Words

to

the

Operator

Qu

ick

Reference . .

Operating

the

3270* . . . . . .

Introduction

to

Display Station Operation

Operator Controls

The Display Image

Indicators .

Keyboards

3

4

5

7,8

8

15-19

20

Typewriter Keyboard*

...............

24

Data Entry Keyboard*

...............

44

Operator Console Keyboard* . . . . . . . . . . . . .

62

Printer Operation* . . . . . . . . . . . . . . . . . . . 76

Operator Identification

Card Reader . . . . . . . . . . . . . . . . .

88

A Typical

Job

. . . . . . . .

Correcting Operator Errors .

Trouble with Your Machine

Operator Trouble Report

Extras for

the

3270* .

Selector Pen . . .

Security Key Lock

Audible Alarm . .

Numeric Lock Feature

Understanding

the

3270*

Data Processing

Display Stations

..

The

IBM

3270

Information Display System

Index

·

90

·

92

.100

· 101

.105

.106

.109

..

110

· 111

· 114

· 115

· 119

*The complete table

of

contents for each section

is

on

the

first page

of

that

section.

I

·"

,.~'

,

I

)

iv

Operator's Notes

We'd

Like

Your

Opinion

I

BM

will

welcome

your

comments on

this

manual,

both

favorable and unfavorable.

Your

name and address

are

needed

for

those

cases

where we

will

want

to

reply.

So,

why

not

let

us

know

what

you

think

of

this book. The

pre-stamped, pre-addressed Reader's Comment Form at the back

is

your

communications

link

with

the author. Write

your

comments on the

form

and drop

it

in

the

mail.

First Words to the Operator

As a

3270

Information Display System

operator

you may

operate

display stations, selector pens,

or

operator

identification

card readers, depending

on

the

equipment

needs of

your

organization. You may also be required

to

monitor

the

operation

of

printer

units.

The

purpose

of

this manual

is

to

help you

prepare

for

these various operating tasks.

Readers

of

this manual need no previous knowledge

of

computers, display system

equipment,

or

data

processing.

General background information

is

provided

to

introduce you

to

data processing and computers. If you have no experience

in

this

area, begin by reading

the

section entitled "Understanding

the

3270";

it

is

the

section

at

the

back

of

the

book

that

has

black-tabbed pages. With

the

knowledge gained

there,

you should

have no

trouble

with

the

section titled "Operating

the

3270".

If

you are already an

operator,

you may find this

book

helpful as a

reference source.

Operator

controls, indicators, and keys for

a"

models

of

3270

display stations, keyboards, and printers are discussed

in

detail

along with typical operating and

error

recovery procedures.

In

this

book

.....

.

. . . . . .You wi" find operating instructions

and

operating

tips

for

the

versatile

IBM

3270

family

of

display

stations.

.

.....

You will

take

your

first

steps

on

the

road

to

an interesting and rewarding career

opportunity.

If

you are going

to

operate

a display station, you wi" find

instructions beginning

on

page 5.

If

you

are interested

in

printer

operations, refer

to

page 76.

Instructions

for

using

the

operator

identification card reader

are given

on

page 88.

Selector pen operation

is

described

on

page 101.

1

2

Operator's Notes

We'd Like

Your

Opinion I

BM

will

welcome

your

comments on

this

manual, both

favorable and unfavorable.

Your

name

and

address

are

needed

for

those

cases

where

we

will

want

to

reply.

So,

why

not

let

us

know

what you

think

of

this book. The

pre-stamped, pre-addressed Reader's Comment Form at the back

is

your

communications

link

with

the author. Write

your

comments on the

form

and drop

it

in the mail.

POWER SWITCH

\

Adjust

Brightness

Adjust

Contrast

SYSTEM

AVAILABLE

INPUT

INHIBITED

INSERT MODE

SYSTEM

READY

SYNC SEARCH

SELECTED

STATUS

TRANSMIT

Quick Reference

INDICATORS

System

will

accept data or signals

from

your

display station.

Turns

on

if

you:

1.

Attempt

to

change protected data.

2.

Attempt

two

input

operations at the

same

time (card

reader, selector pen, keyboard).

3.

Insert

too

many characters

into

a field (Insert Mode).

4.

Press

CLEAR, ENTER, TEST REO,

or

any PA

or

PF

key. Turn

off

with

RESET key.

Insert characters

into

displayed data.

Turn

on

with

INS

MODE key.

Turn

off

with

RESET key.

Your

display station

is

ready

to

communicate

with

the

system.

Your

display station

is

available

for

selection by the

computer.

Your

display station

is

selected

by

the computer.

Your

display station

is

giving the computer its status

(usually error status).

Your

display station

is

transmitting

to

the computer

(over telephone lines.)

KEYBOARD

o

DOOOOOOOooLJoB

00

08000000000000

00

o

0000000000808

OJCD

OCJooooOooOOoCJB8

( )

J(

)(

( )

Typamatic keys repeat

their

function

when held down.

CLEAR

ERASE INPUT

ERASE EOF

INS MODE

DEL

TEST REO

Blanks all

of

screen

and

positions cursor in upper left.

Blanks all

input

fields on

your

screen.

Blanks

from

cursor

to

end

of

field.

Inserts character(s)

into

displayed data.

Removes character(s)

from

displayed data.

Calls

for

testing by the program.

Have

you

tried this?

~I

Tab

~

New Line

tMove cursor up

~

Move cursor down

.-

Move cursor

left

~

Move cursor

right

SOMETHING IS WRONG

Is

this it? . . . . . . .

Display Station

won't

turn

on.

No clicks when keys

are

pressed.

Make sure the power cord

is

plugged

into

the wall outlet.

Is

INPUT

INHIBITED

indicator off? RESET key turns

it

off.

For

more information on troubles,

see

page

92.

3

4 -Operating the 3270

Table

of

Contents

Introduction

to

Display Station Operation

Power (OFF-PUSH) Switch

Brightness Control

Contrast Control

The Display Image

Fields and Formatted Displays

Input

Fields

......

.

Numeric Fields, Data

Entry

Application

High-Intensity Data

Protected Data

Cursor

.....

Cursor Wrap .

Common Indicators

SYSTEM

AVAILABLE

INSERT MODE . . .

INPUT

INHIBITED

3275 Indicators . . .

SYSTEM

READY

SYNC SEARCH

SELECTED

TRANSMIT

STATUS

..

Keyboards

Typewriter

Keyboard (contents)

Data

Entry

Keyboard (contents)

Operator Console Keyboard (contents)

A Typical Job . . . . . . . .

Correction

of

Operator Errors

Trouble

with

Your

Machine . .

Operator's Trouble Report

5

7

8

10

11

12

13

14

15

16

18

19

20

24

44

62

90

92

If

possible, sit

at

a display

station

as you read this

part

of

the

book

so

that

you can use

the

switches and keys as you read

about

them.

By

doing this, you can more quickly become a

skillful

3270

operator.

If

your

display station has a keyboard

attached

and if some

point

is

not

clear as you read, pause

for

a

moment

to

press

the

key

and

watch

the

result. Keep

in

mind,

however,

that

the

purpose

of

some

of

the

control keys

is

to

notify

the

computer

that

your

display station requires service

by

the

program. Pressing any

of

these keys when

the

System

is

ready (SYSTEM AVAI

LAB

LE

indicator

is

on) interrupts

the

program.

In

case you

do

not

have a keyboard provided with

your

display station, you'll only be required

to

make initial adjust-

ments

to

the

display

station

(as explained

in

this section).

If

your

organization has

what

is

called a sign-on procedure

and

your

display station

is

not

signed-on, you can press any key

without

affecting

the

program

or

the

computer. A sign-on

procedure allows

the

program

to

ignore any interrupts received

from an unsigned-on display

station.

There

are many variations

of

the

three

basic

types

of

3270

display stations shown

in

Figure 1

on

page 6. Operating

procedures are similar even

though

screen sizes and appearances

of

some

of

the

units are slightly different.

The

only difference between

the

two

upper displays

is

that

the

larger screen holds

four

times as many characters as

the

small

one. Their indicators and

controls

are

the

same, and display

station

operation

is

identical.

The

labels located

to

the

right

of

the

screen are indicator

names. Display stations like

the

two

top

ones in Figure 1 have no

lights associated with these names. An area

of

the

screen directly

beside each

of

the

three

labels displays a bright square as

an

indication

of

the

associated condition.

The

combination power

on/off

and brightness/contrast con-

trol switch

is

located near

the

screen's lower-left corner (labeled

OFF-PUSH).

The

brightness/contrast control feature

of

the

switch allows you

to

adjust

the

display intensity

to

a comfor-

table

viewing level.

3275

display

stations

like

the

bottom

one

handle

their

own

communications with

the

computer,

usually over telephone lines.

They

have eight indicators

and

use small lights

to

indicate

the

conditions. Three

of

these indicators are identical,

in

name and

purpose, with

the

three

on

all

the

other

display stations.

The

other

five indicators have been

added

to

tell

the

operator

of

the

communications

as

they

are taking place. When

the

indicators are

discussed,

the

three

common

ones

will be presented first,

followed by

the

five

that

are used only on displays like

the

one

on

the

bottom.

Operating the 3270 . 5

INTRODUCTION TO DISPLAY

STATION OPERATION

I

6 Operating the 3270

Figure

1.

There are three basic types

of

3270 display stations.

We

will begin

by

turning

on

power.

We

will

then

proceed

from

adjusting

and

interpreting

the

display image,

through

explaining

the

indicators,

and,

if

your

display

station

uses a keyboard,

to

understanding

all

of

the

keys

on

the

keyboard.

Pull

out

the

switch

labeled OFF-PUSH

to

apply

power

to

your

display

station.

The

red

portion,

visible

at

the

base

of

the

switch

when

it

is

pulled

out,

is

a

reminder

to

turn

power

off

before

leaving

your

display. A delay

of

a

few

seconds

is

built

i'n

to

allow

the

machine

to

warm up.

After

this

delay, a

short

horizontal

bar

will

appear

in

the

upper-left

portion

of

the

screen (in

the

first

character

position

on

Iine one).

When

you

are ready

to

turn

off

your

display

station,

just

push

the

switch

back

in.

Figure 2.

When

the horizontal bar appears, your display station

is

warmed

up and ready

to

operate.

Operating the 3270 7

I

Power (OFF-PUSH)

Switch

8 Operating the 3270

Brightness Control

Contrast

Control

The

Display Image

You can adjust

the

brightness

of

the

characters displayed on

the

screen by turning

the

outer

control

knob

of

the

switch labeled

OFF-PUSH

to

the

left

or

to

the

right. Turning it

to

the

right

makes

the

display image brighter;

to

the

left, dimmer. There

is

no correct setting

for

the

brightness

of

the

image. Experiment

with

this

control

until you find

the

setting

that

is

most

convenient and comfortable

for

your

viewing.

The

contrast

control

is

another

aid

in

adjusting

your

display for

comfortable viewing. If

your

organization uses

two

intensity

levels

to

display characters (explained on page

12,1

under

the

heading "High Intensity Data"),

the

contrast

control varies

the

difference between these

two

levels. (The

contrast

control

is

the

inner control

knob

on

the

OFF-PUSH switch.) As with

the

brightness control,

there

is

no correct setting

of

the

contrast

control; you must experiment until

you

find

the

contrast

level

that

satisfies you.

If

your

display station does

not

have a keyboard

or

selector pen

attached,

you

simply apply power with

the

OFF-PUSH switch

and adjust

the

brightness/contrast controls

to

make

the

unit

ready

for

operation. From this

point

on,

operation

is

controlled

by

the

program, and

you

may only

monitor

information

displayed on

the

screen. If you

do

not

have a keyboard, you

should now read

about

the

indicators on

your

display station (as

described starting

on

page

15

under

the

title

"Common

Indicators").

If

you

do

not

have a keyboard

but

have a selector

pen attached

to

your

display station, read

about

the

indicators

on page 15,

and

then

refer

to

page 101

for

a description

of

selector pen operation. If you have a display station with a

keyboard,

continue

reading this section.

Before we talk

about

the

keyboard,

there

are some things you

should

know

about

what

you can

expect

to

see

on

your

display

screen.

As

we have said before,

the

3270

Information Display System

can be used

by

many different organizations, all with very

different kinds

of

jobs

to

be done. Even within one organization,

there are many different applications

for

3270

display systems.

Today's

computers

are capable

of

processing

many

different jobs

at

the

same time. Therefore, it

is

possible

that

you

could be

working

on

one

job

while

the

operator

you

is

doing

completely different

and

unrelated work.

The

image

on

your

two

screens would probably be completely different.

Figure 3

is

a typical display image;

you

will be referred

to

this

image in some

of

the

discussions

that

follow. Keep in mind

that

this example

is

only

one

of

many possible display images.

Your

organization may

not

even require

this

type

of

image.

The

references made

to

it, however, apply

to

all images.

Figure 3. The image on

your

screen might look like this.

As

you

can see,

the.

display image looks much like informa-

tion

typed

on

a sheet

of

paper. Notice,

too,

that

the

organization

and

content

of

this

form

are

no

different from

the

organization

and

content

of

handwritten

and

hand-processed documents.

The

same

type

of

information

is

always recorded in

the

same areas.

This

is

true

of

all

documents,

as can be seen

by

examining

the

arrangement

of

a

standard

bank

check.

Operating the 3270 9

I

10 Operating the 3270

Fields and

Formatted

Displays

______________

10

__

P.~TOTnE

..!b

OHDEHOE~

________________________

'~

____

__

_____________________________________

D~LL.~H

Figure 4. Bank checks have a standard arrangement.

The upper right portion

is

usuaUy reserved for

the

date. The

center

is

for

the

name

of

the

party

to

whom

the

check

is

made

payable and

the

amount

of

the

check. The lower right portion

usually contains

the

space

for

the

signature

of

the

person writing

the

check.

The various areas

of

bank checks

that

always contain

the

same

type

of

information

or

data are called "fields"

in

data-processing

language, for example,

the

"date" field,

or

the

"signature" field.

Most documents

to

be entered into a computing system will be

organized by fields.

This practice

of

standardizing

the

arrangement

of

data

originated because

the

person using

the

information could do his

job much faster knowing

that

one

type

o(

data would appear

at

the

same location on every document.

When a display station screen

is

divided into fields, it makes

working with

the

display station quicker and easier

for

both

the

display station

operator

and

the

computer program.

The

applica-

tion program divides

the

screen into fields and establishes

the

rules as

to

what

each field will contain. The program

then

knows

that

the

same

type

of

information will always be displayed in

the

same location. Knowing this,

the

program can process

the

data

from

the

screen much quicker. The

operator

can also perform

her

job

more efficiently having this information.

When a screen

is

divided into fields, it

is

known as a

formatted

screen. A screen

that

the

program has

not

divided into fields

is

known as an

unformatted

screen. Each

job

that

you work on

could use a different

format

or

none

at

all; therefore, you

may

be working with

both

formatted

and unformatted screens.

You will see basically

two

types

of

fields on

your

screen.

One

is

primarily

for

the

use

of

the

program;

you

cannot

key

data

into

this

type

of

field.

All

of

your

entries will be into

the

other

type.

For

this

reason,

in

the

remainder

of

this manual, fields

that

you

can key

data

into will be referred

to

as

input

fields

or

input

areas. Each application program User's Guide will tell you which

are

the

input

fields

for

that

particular job.

Once a field

is

assigned

to

one

type

of

data in a job,

those

character

positions should

not

be used

for

other

data

items in

that

job.

For

example,

one

field

on

the

screen in Figure 3

is

called

"Stock

No.".

That

is

the

only

type

of

information

you

will key

into

it. You will

not,

for

instance, key

the

digits

of

a

IIMfg

Code"

number

into

the

"Stock

No."

field. (Otherwise,

the

display

station

keyboard

will

stop

functioning

or

a message will

appear

on

the

screen telling

you

of

the

error.)

There

is

no rule stating

that

fields

must

always be a certain

length

or

that

there

will always be

the

same

number

of

fields

on

the

screen.

The

length

of

a field

is

normally arrived

at

by

determining, from

the

type

of

information which will be

entered

in

the

field,

the

longest possible length

of

one

entry.

In

many

cases,

this

is

known.

For

example, all

Stock

numbers could be

the

same length, 9 digits;

therefore,

the

field

for

Stock

numbers

is

9

character

spaces long. When

the

maximum length

is

not

known, as

in

a field marked

for

customer

name, maximum length

must

be estimated

by

some

method,

and

the

field length

must

be

set

from

that

estimate.

The

number

and

names

of

fields

that

you will see

on

your

screen will

depend

on

the

job

you

are doing and

the

application

program

that

is

operating in

the

computer.

Fields

that

normally

contain

only

numbers (Stock

number,

manufacturer's

code

number,

etc.) are known as Numeric fields.

Such fields

are

used in organizations whose jobs are largely

of

the

data-entry

type.

Rapid

entry

of

numeric

data

is

made possible

by

using a Data

Entry keyboard (described

on

page

45

). When

your

screen

is

formatted,

the

Data

Entry

keyboard automatically shifts

to

Numeric Mode

when

the

cursor

enters

a numeric field. There-

fore,

if

you have a Data

Entry

keyboard, numeric fields help

to

increase

your

operating speed.

Operating the 3270

11

Input

Fields

I

Numeric Fields

Date

Entry

Application

12 Operating the 3270

High-Intensity Data

Protected Data

The

Program User's Guide for

the

program

that

you're

working with designates which are

the

numeric fields.

Figure 3 shows

two

other

features

of

the

3270

which you can

expect

to

see often. The most apparent

of

these

is

called

"H

igh-I

ntensity Data".

This feature

of

the

3270

allows

the

display

of

fields (selected by

the

application program)

at

a brighter than normal intensity.

Use

of

this feature makes

the

high-intensity data stand

out

from

the

other

data displayed

on

the

screen. Many companies make

effective use

of

this feature by displaying

the

field names

at

normal intensity and

the

operator-keyed data

at

high intensity.

Not quite so obvious

in

Figure 3 are

the

protected data fields.

They are

the

fields displayed

at

low intensity.

We

mentioned

before

that,

in most jobs,

there

will be some areas on

the

screen

where you

won't

be able

to

type. You

won't

be able

to

change

field names (titles), for instance.

In

Figure

3,

"Stock

No."

is

a

field name

and

would probably be protected data.

The

protected data feature aids

your

operation because you

don't

have

to

worry

about

making a mistake

and

destroying part

of

the

data on

your

screen.

The

INPUT INHIBITED indicator

will come

on

if you

attempt

to

change (type over, erase, insert,

or

delete characters)

any

data in a protected field.

The

blank field directly following

"Stock

No."

is

the

unprotected stock

number

input field. You would key stock

numbers from

your

source

document

into this

unprotected

area.

The

Program User's Guide for

the

program

that

you're

working with designates which fields on

the

screen contain

protected data

and

which are

your

input areas.

The

cursor

is

probably

the

most

important

characteristic

for

you

to

understand when working

with

the

image. You'll find

that

the

flexibility

of

the

cursor makes operating

the

3270

much easier

and

more enjoyable

than

operating a

typewriter

or

a keypunch.

One advantage

of

the

3270

is

that

the

complete

document

you

are working with

is

always

in

full view;

another

is

that

moving

the

cursor

is

easier and faster

than

repositioning

the

carriage

of

a

typewriter

or

transporting

the

card in a keypunch.

The

cursor appears

on

the

screen as an underline

to

the

character position

in

which

it

is

located.

Figure 5. The cursor looks like an underscore.

That's

right;

it

was

the

cursor

that

appeared

on

your

screen when

you

turned

power on. It marks

the

position

on

the

screen

that

the

entered

from

the

keyboard will occupy. It

may be moved

about

freely

on

the

screen, using certain keyboard

control keys,

without

interfering with

other

characters. You will

also notice, when entering characters from

the

keyboard,

that

the

cursor moves

to

the

right

one

space as each character

is

entered.

You may see

the

cursor apparently changing locations by

itself. However, it can be moved

about

on

your

screen by

the

computer

program, and when

the

cursor appears

to

be moving by

itself

the

program

is

repositioning it

for

you.

Operating the 3270 13

Cursor

I

14

Operating

the

3270

Cursor

Wrap

The cursor control keys

are

located on the keyboard

and

described in the keyboard sections. They move the cursor in

either the horizontal (left

or

right)

or

vertical (up

or

down)

direction

on

the display station

screen.

If

you hold down the

control key

that

moves the cursor

to

the right, the cursor will

move

off

the right side

of

the

face

of

the

screen

and

will reappear

one line lower

on

the

left

side.

This

is

called cursor wrap. In

effect, the cursor wraps around behind the

screen.

It

also

wraps

when moved

to

the left, and

it

will

reappear one line higher

on

the right

side

of

the

screen.

--

----

-...

------

/

~

/ \

I \

\ I

\ /

/

...

------~------

/

"-

/ ,

/ \

I \

I I

\ I

,

/

I

f

I

\

/---"

, /

'-_/

I ""'--,

I

+

I

\

',

__

I

Figure 6. The cursor wraps when you move

it

off

any edge

of

the screen.

Cursor wrap also occurs

when

the

cursor

is

moved

up

or

down. Notice

that,

in

these cases,

the

cursor reappears in

the

same

character

position (on

the

opposite

edge of

the

screen)

that

it

occupied

before moving off

the

screen;

there

is

no shift left

or

right.

In

the

examples in Figure 6, pressing and holding

the

indicated keys when

the

cursor

is

located

at

A moves

the

cursor

to

B.

let's

investigate

the

display station indicators. You already

know

that

they

are located

to

the

right

of

the

screen

on

the

face

of

the

display.

As

you will see,

their

names alone describe

their

functions

quite

well.

SYSTEM

AVAI

lABlE,

INSERT MODE, and INPUT

INHI BITED are

on

all display stations. No

matter

which display

station

you have,

the

purpose

and meaning

of

each

of

these

indicators are always

the

same.

The

SYSTEM AVAI

lABlE

indicator,

on

or

off, will

not

greatly

affect

the

local

operation

of

your

display station. It

is

only

an

indication

that

the

program in

the

computer

is

running

and,

if

your

display

station

has an

attached

keyboard

or

selector pen,

that

it will accept

interruptions

from

your

machine.

If

the

indicator

is

not

on,

the

keys

that

depend

on

the

program

to

accomplish

their

function

will

not

be

effective. In fact, if

you

press

one

of

these keys

when

the

system

is

"not

available",

the

INPUT INHIBITED indicator will come

on

and

data

from

your

keyboard will

not

be accepted.

The

RESET key (described later

in

the

"Keyboard"

sections) will reset

this

condition and

turn

off

the

INPUT INHIBITED indicator.

Operating the 3270

Common Indicators

SYSTEM

AVAilABLE

Indicator

15

I

16

Operating the 3270

INSERT MODE Indicator

INPUT INHIBITED Indicator

The INSERT MODE indicator applies only

to

display

stations

with keyboards. It tells you

that

your

machine

is

in

Insert Mode.

It comes

on

when you press

the

INS

MODE key.

To

turn

it off,

press

the

RESET key

on

the

keyboard.

Insert Mode allows you

to

insert a character,

or

characters,

into an existing line

on

your

screen

without

destroying

any

of

the

data already there.

The

new characters are inserted

at

the

cursor location,

and

the

data

to

the

right

of

that

location.

is

shifted right

one

character position

for

each

character

inserted.

Later, when you read

the

discussion

for

the

INS MODE key

in

your

keyboard section, more details

and

an example

of

an

Insert

Mode operation will be presented.

The

INPUT INHIBITED indicator tells you

that

all

of

the

input

devices

on

your

display

station

are disabled. You

cannot

key any

data from

your

keyboard

or, if you have a Selector Pen, you

cannot

select

any

items with it.

If

a display

station

is

installed

without

a keyboard, selector pen,

or

operator

identification card

reader,

the

INPUT INHIBITED indicator will light

only

under

program control. Before explaining

the

conditions

that

cause a

display

station's

input

devices

to

be inhibited, we will discuss

the

way in which

your

keyboard

is

disabled.

There

is

no

mechanical keyboard lock associated with

preventing

the

use

of

the

keyboard, such as

there

is

on

keypunch

keyboards.

That

is, when

input

is

inhibited,

the

keys on

your

keyboard are

not

physically locked

in

one

position; you can still

press

them

down normally. On

your

display

station,

when

input

is

inhibited,

the

keyboard's

electrical circuits (triggered

by

pressing

the

keys) are deactivated, and

the

click

that

you

normally hear when

any

key

is

pressed stops.

The

result

is

like

pressing

the

keys when

your

display station

is

turned

off;

they

go

down,

but

nothing happens.

The

reasons

why

the

INPUT INHIBITED indicator will come

on

are:

1. If you

attempt

to

change,

in

any

way,

the

data

contained

in

a

protected

field, INPUT INHIBITED will

turn

on

and

your

keyboard will be disabled.

IBM 3270 Manual

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