3270 Keyboard Reference

The tn3270.ttkeyboard file must be in UTF-8 format. All lines in the tn3270.ttkeyboard file must end in a line feed or a carriage return/line feed pair. All settings are case-sensitive.

The default tn3270.ttkeyboard files are available for download:


These settings identify specific keyboard layouts and set off comments.

  Setting   Description

+ Name keyboard layout and begin section. Also ends previous keyboard layout if one is present. A period in the name identifies the layout as subordinate to another layout with the same name, but without the dot extension. It also prevents the layout name from being displayed in TinyTERM. For example, +QWERTY.L.shift is a subordinate layout of +QWERTY.L.
# Comment line. These can be inserted anywhere in the tn3270.ttkeyboard file.
# QWERTZ layout in landscape mode

General Settings

These settings can be placed anywhere in the tn3270.ttkeyboard file, preceded with a dash. They will affect all lines below them, until a new instance of the setting is found.

  Setting   Description

fontSize Maximum font size in points of main key labels. The label size will be reduced automatically to fit the key if needed.
-fontSize 20
keyHeight Changes the default height of the keys, relative to a base value of 1. keyHeight can be specified to the second decimal place, as in the example below. It cannot be set to a specific number of pixels. Default key height in pixels is calculated instead, based on the number of key rows, the spacing and margin settings, iPhone orientation, and individual keys not using the default keyHeight value.
-keyHeight 1.44
lineJustification Sets the justification for rows of keys:
0 center (default)
1 left justify
2 right justify
-lineJustify 1
margin Minimum clear space on each edge – top, bottom, left and right – of the keyboard.
-margin 3
size Changes the default width of keys, relative to a base value of 1. size can be specified to the second decimal place. It cannot be set to a specific number of pixels. Default key size is calculated instead, based on the number of keys in the widest row, the spacing and margin settings, iPhone orientation, and any individual keys not using the default size value.
-size 1.5
spacing Minimum space between keys
-spacing 2

Key Options

When a key is defined within square brackets [ ], options may be added to the definition, set off by two semicolons. Many of the general settings can also be applied to individual keys, and so are repeated below with key-specific examples. Options are all case-sensitive.

When a semicolon is desired as a displayed character inside the brackets, such as for a label, separate it from the double semicolons by a space. Then use keyString to set the character, so the space isn't typed as part of the key:

[; ;;size=0.82;;keyString=\x003b]
  Option   Description

\ Escape character. Used for special characters that have other uses without the \. Square brackets are not required for this option.
blank When set to 1, prevents the key from being drawn. Used for creating space between visible keys in addition to that specified by the spacing attribute. Blank keys are treated as any others by general attributes.
capsKey When set to 1, causes the key to act as a Caps Lock key, regardless of other settings.
hideKey When set to 1, causes the key to hide the keyboard when tapped. Also replaces any text with a keyboard graphic. The keyboard can be restored by tapping the keyboard button in the title bar, or by double-tapping the screen.
fontSize Sets the font size for the primary label of the key.
keyChar Assigns a specific value to a key. Available values are listed below.
keyHeight Changes the height of the individual key, relative to a base value of 1. keyHeight can be specified to the second decimal place. Keys taller than the default for the row expand into the next row down. When making single a key taller than 1, free the space in the row below by creating a key there with the blank option.
[New Line;;keyHeight=2;;keyChar=1153]
keyString Assigns a multi-character string to a key. This allows you to create custom key mappings with multi-byte sequences on a single keystroke.
printScreen When set to 1, this key will print the current emulator screen. Defaults to 0.
shiftId Changes the identity of a shift key. By default, the ID for a given shiftTo or shiftLock key is the layout it refers to. This option overrides that behavior, giving the key a unique ID.
shiftLock Used without shiftTo, takes a keyboard layout name. The selected layout will replace the current layout.
Used with shiftTo, takes a numeric value that determines how the key works. Also requires a shiftId label to identify the layout to return to.
0 Hold-shift: hold key down for shift characters
1 Lock-shift: switch to another layout until tapped again
2 Single-shift: tap to shift. On typing a shift character, revert to original layout.
3 Double-shift: hold to shift temporarily, or double-tap to lock-shift.
4 Single-shift with double-shift: tap once to shift as with 2 above, or double-tap to lock-shift as 3 above. (default)
shiftTo Selects a keyboard layout to display while key is held. The selected layout will replace the current layout until the shift key is released.
size Changes the width of the individual key, relative to a base value of 1. size can be specified to the second decimal place.

Special Characters

The following characters are created with the escape character \.

  Character   Value   Character   Value

\b backspace (hex 08) \\ backslash (hex 5c)
\[ left square bracket (hex 5b) \] right square bracket (hex 5d)
\r carriage return (hex 0d) \x UTF-8 hexadecimal number; e.g., \x000d for carriage return
\t horizontal tab (hex 09) \0 octal constant; e.g., \011 for horizontal tab

Note that all hexadecimal and octal values are for the ASCII character set for iOS compatibility. TinyTERM Enterprise for Android converts these to EBCDIC during communication with the mainframe system.

Special characters may be used in combination with the keyString option to create complex sequences:


keyChar Values

The following values may be assigned to keys, using the keyChar option. Values not listed have been reserved, and are not available.

  Value   Keyboard Key   Value   Keyboard Key

0-255 Equivalent ASCII character1 62560-62583 PF1 to PF24
8 Backspace ⌫ 62584-62586 PA1 to PA3
9 Tab 62587 Back Tab
13 Enter (CR) 62588 Clear
63232 Up ↑ 62589 Erase Input
63233 Down ↓ 62590 Erase End of Field
63235 Right → 62591 Attn
63234 Left ← 62593 New Line
63273 Home 62602 Field Mark
61740 Insert 62603 Dup
61741 Delete

1As with the \x and \0 special characters, ASCII values used with keyChar are converted to EBCDIC during communication with the mainframe.

Putting It All Together

As seen above, there are a variety of options for defining keyboard keys in TinyTERM. Combined, they can create just about any key design needed. Here are three examples from the QWERTY portrait layout. They all use these default values:

-spacing 3
-margin 0
-keyHeight 1.4
-fontSize 20


The first argument (here K) is always the key label. keyString causes the key to send a lower-case k. Without it, the key would send the label instead, upper-case K. Labeling like this gives an appearance like that of a physical keyboard.


This key uses keyChar instead of keyString to send a non-printable ASCII 13, which is the carriage return ^M. The fontSize argument makes the label text smaller than the default point size 15. labelPosition=6 overrides the default value to left-justify the label string in the lower left corner of the key. And size makes the key even wider than the K key described above.


This particular key comes from a shifted layout, rather than a main one. shiftTo shows which layout will be displayed when this key is tapped. shiftId gives this key a unique identifier, so that it properly uses the default shiftLock behavior.

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