Written and Maintained by Gregory Nacu


Last modified: Jun 21, 2021

Chapter 4: The User Interface

C64 OS is an immersive computing environment. Once you boot into C64 OS, you can move from application to application, performing different tasks and managing your computer's hardware and resources, without having to shutdown or restart your computer.

As soon as C64 OS has booted, the mouse pointer becomes active. The mouse allows you to select text, drag things to move and arrange them, and click on buttons and other user interface controls to change tabs, resize screen areas, select between options, scroll through content, and start and stop processes. With the mouse you can also choose options from the pull–down menus to command and control the many features in C64 OS applications.

In addition to mouse input, C64 OS has rich and extensive support for keyboard input. The keyboard can be used to make selections, input text, flip pages, scroll lists, change tabs, copy and paste data to and from the clipboard, and trigger the most frequently used menu options.

C64 OS App Launcher with Memory Utility. C64 OS File Manager with Utilities Utility.

This chapter gives you an overview of the common elements of the C64 OS user interface, the menu bar, status bar and toolkit controls. C64 OS is intuitive and easy–to–use, but there are also many power–user features that make your interaction with your C64 faster and more efficient.

The Menu Bar

The menu bar is a central user interface element of C64 OS.

The menu bar runs along the top edge of the screen and provides snappy, pull–down, hierarchical menus with configurable multi–modifier keyboard shortcuts. Menu options are used to open Utilities and send commands and toggle options in Applications. The menu bar is divided into three main sections. The utilities menu is on the left, the application's menus are in the middle, and the time is optionally displayed on the right end.

Labeled diagram of the menu bar regions.

To activate the menus, press and hold either mouse button while the mouse pointer is over the menu bar. As you pass the mouse over a top–level menu option, its submenu drops down automatically. If you roll onto another a menu option, its submenu drops down and the the previous submenu automatically snaps shut. Multiple levels of nested submenus are supported. Menu options change to a highlighted color while the mouse pointer is over them, to help you know which one will be selected. Release the mouse button to select the highlighted option and close the menus.

Depending on the state of the Application, some menu options appear in a disabled color. Disabled menu options do not highlight when you mouse over them, and they cannot be selected either with the mouse or with their corresponding keyboard shortcut.

Menu options can also display a checkmark to the left of their title. A checkmark indicates that the menu option is active.

To the right of a menu option's title text may appear an optional keyboard shortcut. Keyboard shortcuts are expressed by a series of one or more modifier key symbols followed by a letter, number of symbol key. The modifier keys are SHIFT, CONTROL, and COMMODORE. Either shift key, including the Shift Lock key, can be used to form a modifier combination for the menu shortcuts.

Shift Key Symbol. Control Key Symbol. Commodore Key Symbol.

To trigger a keyboard shortcut, the menu option must be enabled. Press and hold the specified modifier keys concurrently and then press the specified letter, number or symbol key. The top–level menu option, under which the triggered menu option is found, highlights briefly to provide feedback that the keyboard shortcut had an effect.

The Utilities Menu

From the leftmost end of the menu bar you can open the Utilities menu.

The Utilities menu works much like the rest of the menu bar. When the menus are open you can roll the mouse pointer between it and the Application's menus, and they open and close the same way. The Utilities menu can also contain submenus and its menu options can have keyboard shortcuts. However, options selected from the Utilities menu do not send commands to the Application the way normal menu options do. Instead, they open the Utility whose name is the title of the menu option.

The Utilities menu is managed by the system. Its contents and organization are customizable, but that content stays the same as you change from one Application to the next. Typically the Utilities found in the Utilities menu are ones that are useful to have access to from within any other Application. For example, it would be useful to have access to the Calculator at any time.

Other Utilities found in the Utilities menu, in the default configuration, include:

Utility Purpose
About This App Shows information about the current Application.
Such as its version number, author and copyright
year, as well as the Application's icon.
Settings Gives access to a number of other C64 OS Utilities
that are geared around managing system settings and
hardware configuration.
Utilities Shows a list of all installed Utilities. With this
Utility available, it is possible to get access to
every installed Utility from within any Application.

The contents of the Utilities menu are specified in the file:


See the C64 OS Programmer's Guide, for more information about how to customize a menu definitions file.

The Application's Menus

All of the remaining top–level menu options, following the leftmost option for the Utilities menu, are provided by the current Application.

Each Application contains a menu definitions file within its bundle directory. An Application's menus are constructed automatically when the Application is launched. This means that the contents of the menu bar, for the Application's menus, changes depending on the Application that is currently running.

The Application controls which menu options are enabled or disabled and which ones show the active checkmark, by responding to menu enquiry messages. Each menu option, whether it is selected with the mouse or triggered by its keyboard shortcut, sends a unique action code to the Application via a menu command message.

There are several advantages to the separation of the menu structure and the Application receiving menu enquiry and command messages:

  • It opens the future possibility of translating menu definition files to other languages.
  • Advanced or beta features may be concealed by removing their entries from the menus.
  • Menus may be rearranged and keyboard shortcuts may be reassigned without changing the Application.
  • Messages can be sent programmatically, allowing a script or other program to control a C64 OS Application.

For more information about how to customize a menu definitions file and the structure of an Application's bundle directory see the C64 OS Programmer's Guide.

The Date and Time

On the right side of the menu bar is the time. The system time is configured during bootup by one of several realtime clock drivers that C64 OS provides.

The display of the time can be customized for 12 or 24 hour mode, and the colon can be configured to blink each second or remain solid. C64 OS can also be configured to boot up with the time hidden. You can toggle the display of the time by holding the COMMODORE key and clicking once on the right end of the menu bar. Hiding the time provides more horizontal room for Application menus.

When the time is displayed it can be double–clicked to open a Utility. Which Utility gets opened can be customized, but by default C64 OS opens the Today Utility. Today is a simple calendar that highlights the current date in a month view, and lets you cycle backwards and forwards through the months.

See Chapter 8: Utilities for more information about the Today Utility.

Special Menu Bar Options

The entire menu bar may be hidden or shown, either programmatically, (for example, an Application may choose to automatically hide the menu bar,) or at any time with the system–wide keyboard shortcut:


This keyboard command can be customized using the C64 OS Configure Tool.

Hiding the menu bar opens up more screen real estate. Whenever the menu bar's visibility is toggled a message is sent to the Application. Applications respond to this message by dynamically adapting their user interface to fit the available screen space.

The Status Bar

The second most central user interface element of C64 OS is the status bar.

The status bar runs along the bottom edge of the screen, and always floats above other content. The status bar provides useful information at a glance, including available main memory, last accessed drive status message, selected file count, path to open or selected file and more. The status bar has three modes:

  • Drive Status mode
  • Open or Selected File mode, and
  • Application Custom Message mode.

Not every mode is available in every Application. Click once anywhere on the left side of the status bar to cycle it to the next available mode.

Drive Status

In drive status mode the status bar is divided into two sections. The main section on the left shows the most recent status message from the last accessed drive. The right end shows the currently available main memory.

The status message is mostly in the same format as the drive returns it, except that the device number followed by a colon appears before it. That tells you which device this status message comes from.

Labeled diagram of the status bar in drive status mode.

IDE64 Technical Note

Most Commodore 64 drives output their status message in the format:

00,message text here,00,00

But IDE64 outputs a longer status in the format:

00,message text here,000,000,000,000

C64 OS only shows the least significant 2 digits of the first two status numbers following the textual message. This captures the most relevant information while keeping the format the same as other C64 drives.

Output of the drive status is automatically managed by the system. Applications do not need to opt–in to support it. All Utilities and Applications which make use of the C64 OS file routines for disk access are automatically integrated with this status bar mode.

Open or Selected File

C64 OS has a standard pointer which Applications use to indicate which file is currently open or selected. For example, when a text editor is editing a file, the standard pointer points at a reference to that file. Or, for another example, when a C64 OS image viewer is showing you a picture, the standard pointer points at a file reference to that picture file.

If an Application, such as the File Manager, presents a directory of files, the standard pointer is used to indicate the selected file. This standard pointer enables other processes to act or operate on that file. The status bar in open or selected file mode is an example of just that. The status bar shows you the name and location of the file that the Application has open or selected.

Labeled diagram of the status bar in open / selected file status mode.

In this mode, the main left section of the status bar shows the file in the C64 OS standard file reference format. The section on the right end of the status bar shows the currently available main memory.

If the Application does not have any file open or selected, the status bar automatically skips this mode and cycles into the next available mode.

The standard file reference format is as follows:


For more information about C64 OS file references, see Chapter 5: File System.

Application Custom Message

Each Application may opt to support a custom status message. When the status bar mode is cycled, if the Application does not provide a custom message it automatically skips to the next available mode.

An application's status consist of any plain text PETSCII string. The system sets the text color to match the status bar color, and displays up to a maximum of 40 characters. In this mode the currently available main memory is not displayed, and instead the entire width of the status bar is available for the Application's custom use.

The Application can change its status message at any time and notify the system that it has changed. If the status bar is in Application custom message mode, it immediately redraws the new content.

Labeled diagram of the status bar in Application custom message mode.

Applications can use the custom message mode to display all variety of information such as:

  • The Application's name
  • The number of selected files
  • The number of lines or words in a text file
  • Some metadata about an open file
  • etc.

Special Status Bar Options

The entire status bar may be hidden or shown, either programmatically, (for example, an Application may choose to automatically hide the status bar,) or at any time with the system–wide keyboard shortcut:


This keyboard command can be customized using the C64 OS Configure Tool.

Hiding the status bar opens up more screen real estate. Whenever the status bar's visibility is toggled a message is sent to the Application. Applications respond to this message by dynamically adapting their user interface to fit the available screen space.

The currently available main memory indicator can be configured to show free memory as either kilobytes or 256–byte pages. Showing in kilobytes may be more comfortable for users of modern computers, but it is slightly less accurate than pages. Additionally, the File Manager lists file sizes in disk blocks and a disk block is roughly the same size as a memory page. For these reasons, although kilobytes is available as an option, showing the memory count in pages should be considered more native to C64 OS.

When the available main memory is displayed it can be double–clicked to open a Utility. Which Utility gets opened can be customized, but by default C64 OS opens the Memory Utility. Memory shows a visual overview of how main memory is currently allocated, using a color–coded key to indicate several different allocation types.

See Chapter 8: Utilities for more information about the Memory Utility.

Split Screen and Fullscreen Graphics Mode

C64 OS's main user interface is based on the VIC–II's character mode. A custom character set enables visual elements to be used to build up a graphical user interface. The VIC–II's character mode is incredibly fast, which is why it is used in arcade games to provide fast and smooth fullscreen scrolling.

However, there are times when an Application needs to display bitmapped graphics. One example is to show a picture. Splitting the screen on a C64 requires notoriously tricky and precise timing, but C64 OS's KERNAL and status bar have low–level features which—in conjunction with a graphics library—provide Applications an easy–to–implement split screen mode.

Split screen mode allows the top portion of the screen to display the C64 OS primary user interface, while the bottom portion of the screen displays bitmap graphics in either Hires or Multi–Color mode. When graphics data is available, you can simply click and drag the status bar up from the bottom of the screen, and put it on any screen row, all the way up until the status bar meets the menu bar.

The status bar continues to work exactly as before, but in a new position partway up the screen. The bitmap graphics display immediately below the status bar, to the bottom of the screen.

The Gallery app, in character mode. The Gallery app, in split screen mode.

In addition to split screen mode, whenever graphics data is available, you may toggle between split screen mode and fullscreen graphics mode using a system–wide keyboard shortcut:


This keyboard command can be customized using the C64 OS Configure Tool.

When toggling out of fullscreen graphics mode, the split is restored to exactly where you left it, including the split mode being fully closed.

The Gallery app, in split screen mode. The Gallery app, in fullscreen graphics mode.

In order for split screen or fullscreen graphics mode to be active, the Application configures special system properties that specify the location and format of the bitmap data. If these properties change to indicate that bitmap data is no longer available, the system automatically switches out of fullscreen graphics mode and snaps the split screen shut, moving the status bar back down to the bottom of the screen.

Usage Note

Split screen and fullscreen graphics mode cannot be used simultaneously with a C64 OS Utility. Due to memory constraints, Utilities are loaded into the bitmap memory area. When a Utility is opened, C64 OS toggles out of fullscreen bitmap mode and shuts the split screen mode automatically.

When the Utility is closed, the Application is sent a message and can reconfigure the bitmap graphics pointers, but the split screen is not automatically reopened.

When in split screen mode the user interface visible above the split, including the menu bar and status bar, is fully active and can be interacted with as normal. Additionally, bitmap graphical content displayed below the split is not limited to showing a static image. Interactive bitmap content can be displayed below the split, allowing for both mouse and keyboard input.

The NESTester app, in split screen mode. The NESTester app, in fullscreen graphics mode.

In the examples above, the menu is shown selecting an optional game controller driver for use in the NESTester Application with split screen mode active. And in fullscreen mode, you can click on the port buttons to change which control port is being tested. Pushing buttons on the gamepad controller (or any joystick) highlights the button or buttons being pressed in the bitmap image.

In the examples below, the Chess Application shows that bitmap graphics can offer significant mouse interaction. Whether in split screen or in fullscreen graphics mode, you can click on a chess piece, its available valid moves and the pieces it can take are highlighted, and you can drag the piece around the board to drop it in its desired place.

The Chess app, in split screen mode. The Chess app, in fullscreen graphics mode.

The Status Bar and Split Screen Mode

Applications can change state at any time. An Application could make bitmap graphics available at one time and unavailable at another time, depending on the sensible behavior for what that Application does. This could leave you uncertain about when split screen mode is and is not available.

To help you out, whenever split screen mode is available the status bar shows an up arrow icon next to the available memory icon. The up arrow is a reminder that you can grab the status bar and drag it up to reveal what is behind the main user interface.

The status bar showing a split screen indicator.

Note that this extra status icon is only visible when the available memory is visible. It is, therefore, not visible when the status bar is in the Application Custom Message mode.

Applications and Utilities

An operating system is, among other things, a software platform. In C64 OS there are two kinds of programs. There are Applications (with a capital A when referring to a proper C64 OS Application), and there are Utilities (again, with a capital U to distinguish proper C64 OS Utilities from ordinary utilities for other platforms.)

Applications run in fullscreen mode extending from the menu bar to the status bar. They provide a set of menus which are used to control the Application's functions. And they often integrate with the status bar by providing it custom content. There is always one Application running.

Concurrently with the Application, C64 OS may optionally run one Utility. Utilities, typically, run within a movable panel that floats above the Application's user interface. Some Utilities are fully self–serving, providing you with some useful functionality, such as the Calculator. Other Utilities are designed to interact more closely with the Application, providing it supplementary services, such as a color picker, a date picker or a word counter.

After booting up you are taken to Homebase, either App Launcher or File Manager, whichever one you were in last. Both are considered Homebase and you can switch between them via an option in the Go menu. From Homebase you can launch an Application. To leave an Application, choose Go Home from its menu options, or use the standard keyboard shortcut:


Although a Utility can be run concurrently with an Application, when you switch Applications any Utility that is open is first closed. Applications and Utilities automatically save and restore their state.

Useful Information About Applications

Most Applications are installed in the applications directory in the system directory.


A few Applications, which are critical to the functioning of C64 OS and which cannot be uninstalled, are found in the services directory in the system directory.


Applications are composed of a structured directory bundle. The directory bundle is named for the Application and contains a standardized set of resources, including:

  • a main executable
  • an initialization executable
  • an icon
  • a menu definitions file
  • an about metadata file
  • state and configuration files
  • help files, and other resources

To install a new Application, its bundle directory need only be copied to the system's applications directory. To uninstall an Application, its bundle directory can either be scratched or moved to some other place. Because an Application's resources are all contained within its bundle, nothing is left behind after uninstalling it.

Applications may programmatically open Utilities, and can also pass a message to a Utility to be processed immediately upon opening. This enables Applications to offload many of their common features to Utilities, and allows standard Utilities to be shared by many Applications.

The File Manager launching. The File Manager after it has launched.

When an Application is loading, the loading screen (above, left) is shown. This shows the Application's icon and the path where the Application is installed.

For more information about the App Launcher see Chapter 6: App Launcher.
For more information about the File Manager see Chapter 7: File Manager.

Useful Information About Utilities

All installed Utilities are found in the utilities directory in the system directory.


Utilities are much simpler than Applications. A Utility does not have a bundle directory and consists of just a single file.

If a Utility is open when another one is called to be opened, the first saves its state and then closes automatically. There are several ways to open a Utility:

  • Select a Utility from the Utilities menu
  • Double–click the time in the menu bar
  • Double-click the available memory indicator in the status bar
  • An Application can open a Utility
  • A Utility can open another Utility

A Utility presents itself in a movable panel. When first opened a Utility takes keyboard focus; key presses and commands are sent to the Utility first. If a keyboard event is not handled the Utility typically passes it along to the Application. However, if you click on the Application behind a Utility, the Utility loses keyboard focus and stops processing keyboard events. Click anywhere on the Utility to bring it back into focus.

Technical Note

Utilities may optionally present as modal. When a modal Utility is open all of the menu options are disabled and mouse and keyboard events are prevented from affecting the Application.

A modal Utility may still be moved so you can see what is below it, and the Application is still active. Animations, timed or network–related events can still change an Application's appearence below a modal Utility.

Drag a Utility by its title bar to anywhere on the screen, including partially off the left, right or bottom edges. When the menu bar or status bar are visible, they prevent a Utility's title bar from being dragged behind them.

Click the close button on the left end of the title bar to close a Utility.

Hold the CONTROL key and click anywhere on the title bar to collapse a Utility so that only its title bar is visible. This is called window shade, and is a fast and convenient way to see what is behind a Utility without needing to move it.

Title bar, close button and window shade of Utilities.

Message Passing

Utilities and Applications send messages to each other. Either side can try to send any message without knowing if the other side supports it. When a message is understood a reply is sent that the message was handled. All other messages get safely ignored and a reply is sent that the message was not handled.

Different Applications may handle the messages from the same Utility in different ways. And vice versa, different Utilities may handle the same messages from an Application in different ways. This system makes Applications and Utilities only loosely tied to each other, and allows for many creative combinations to emerge.

The Toolkit

The Toolkit is a suite of user interface elements which can be created, configured and snapped together like lego pieces. C64 OS Applications and Utilities can use them to build powerful and consistent user interfaces with a minimal investment of code and development time.

Each Toolkit interface element has its own appearence, behaviors, tricks and shortcuts which you can learn and get used to. When a standard interface element is used in more than one Application, your knowledge about how to use it helps you out in many different contexts. This way, an Application's use of the Toolkit helps make the experience of using C64 OS consistent.

The following standard user interface elements are explained and explored:

Push Buttons

One of the most simple controls is a push button. Click on a button, it highlights momentarily to give you feedback that you clicked it, and some action is performed.

A button can also be disabled. A disabled button takes the same color as a disabled menu option. If you click on a disabled button it does not highlight and no action is performed.

Often in a user interface one of the buttons is a default button which is displayed in an alternative color. Push the RETURN key to trigger the default button.

Disabled push button, push button and default push button.

Cycle Buttons and Periodic Buttons

Some buttons have a cyclical–arrows icon before the button title. These are called cycle buttons. When you click on a cycle button its title changes, in addition to performing some other action. If you click a cycle button repeatedly it eventually circles back around to show the same title again.

Hold the COMMODORE key and click on a cycle button to cycle through the options in reverse order. This is very convenient, allowing you to click through options quickly without worrying about going past the one you want. If you go to far, just hold the COMMODORE key and click to step backwards.

Some buttons—either cycle buttons or regular push buttons—are called periodic. If you click and hold on a periodic button the button's action is performed repeatedly. A periodic cycle button repeatedly cycles through its options.

Cycle buttons, push button and default push button.

Checkboxes and Radio Buttons

Checkboxes and radio buttons are special kinds of buttons that add active and inactive states, indicated by an icon to the left of the title. The title of a checkbox or radio button is part of the button, (like an ordinary button but without the bounding box,) so you can click the icon or the title to trigger it.

Checkboxes work independently. Click on a checkbox to toggle its state from active to inactive or vice versa. Some other action may also be triggered.

Radio buttons always come in groups of two or more. Only one radio button in a group can be active at a time. Click on a radio button to make it active and the previously active radio button is deactivated automatically. Some other action may also be triggered.

Checkboxes and radio buttons can be disabled, just like normal buttons. A disabled checkbox or radio button shows in the disabled color and clicking it does not change its state or trigger any other action.

Cycle button, checkbox button, default push button, and radio button pair.


User interface elements are collected together in a rectangular area of the screen to provide some functionality. But sometimes there isn't enough room to show everything in one area at the same time. To increase how much room is available, areas can be overlapped or stacked one on top of the other. To access each of the overlapped areas a series of buttons appear in a row along the top of the stacked areas.

There can be from two to ten tabs in one tab group. Each tab has a title and the tabs automatically resize themselves to divide up the space. If a tab is not wide enough to show its full title, the end of that title simply gets clipped.

Clicking a tab highlights it momentarily to give you feedback that you clicked it. However, the Application has the ability to prevent tabs from switching, depending on what's going on in the tabs.

The currently active tab has a color that indicates that it is selected, and all the other tabs show in another color to indicate that they are unselected.

Group of four tabs, one selected, three unselected.

Groups of tabs can be nested inside other tabs, but a well designed Application only does this if it really makes sense. Tabs are often used to group common controls together and separate them from other unrelated controls.

Different default push buttons can appear in each tab area. Default buttons in unselected tab areas don't get activated when the RETURN key is pressed.


While tabs allow multiple areas to be stacked one atop the other, with only one of them visible at a time, splitters allow two areas to be positioned beside each other, left–to–right or top–to–bottom, with a dividing bar between them called a splitter bar.

The splitter bar has a grippy icon to indicate that it can be grasped and dragged. The whole bar can be dragged allowing you to devote more screen real estate to one area and less to the other. You can reallocate the space whenever you want.

A user interface with a vertical splitter.

Any content can be added to the areas on either side of the split, including another splitter. Like nested tabs, a well designed Application does not take nesting splitters too far, but it can be effective when it's appropriate.

There are cases when the right edge of the left area of a split (or the bottom edge of the top area of a split) already has a prominent visually dividing element. In this case a splitter bar can be collapsed which saves space and often looks better. When a splitter bar is collapsed it can only be dragged by the grippy icon, which is still visible but is drawn overtop of the corner of the left or top split area.


When there is too much content to fit in an area of the screen, and it is inappropriate or impractical to divide the content into tabs, the area can instead be turned into a scrollable area.

An area on the screen can be configured either to be vertically scrollable, horizontally scrollable, or both.

When an area is vertically scrollable, a scrollbar appears along its right edge. When an area is horizontally scrollable, a scrollbar appears along its bottom edge. The background of a scrollbar's track is diagonally striped, and the scroll nub is solid. Two scroll buttons appear together at the bottom of a vertical scrollbar or at the right end of a horizontal scrollbar. If both scrollbars are enabled, this puts all four scroll buttons physically close to each other so you don't need to move the mouse far to select between them.

If the content within is shorter or narrower than the visible area, in other words, if all the content can be seen without needing to scroll, the scrollbar switches to a disabled state. It gets colored the same as other disabled elements, such as disabled buttons or menu options.

When content is longer or wider than the visible area, the scrollbar becomes active. The size of the scroll nub is proportional to the percentage of the content that is visible. If you can see 90% of the content but need to scroll to see the final 10%, then the scroll nub is drawn as 90% of the height of the track in which the nub slides. If you can see only 50% of the content, the nub is drawn as 50% of the height (or width) of the track.

Disabled vertical scrollbar, horizontal scrollbar, and vertical scrollbar, showing nub and buttons.

There are several ways to scroll content using a scrollbar.

Click once on one of the scroll buttons to scroll in that direction. The content scrolls a few lines with each click. The scroll buttons are periodic buttons. Click and hold on a scroll button and the content scrolls continuously, a few lines at time.

The scroll buttons have two hidden features. You can slow down the scrolling and cause the content to scroll more precisely—only one line at a time—by holding the SHIFT key while clicking on a scroll button. Alternatively, you can speed things up. Hold the COMMODORE key and click on a scroll button to scroll the content all the way to the end, in that direction, in a single step.

The fastest and most convenient way to scroll through a lot of content is to click and drag the scroll nub. The content scrolls proptionally to how fast you move the scroll bar. If there are 500 of lines of content, and you drag the scroll bar half the distance in just one second, then you scroll the content by 250 lines in only one second.

You can also scroll by clicking on the striped track itself. Click on the track above the scroll nub to scroll up, one page at a time, or on the track below the nub to scroll down one page at a time. The size of a page is equal to the number of visible rows less one. If you can see 20 rows of content, clicking the track scrolls the content 19 lines. The single line of overlap between pages helps your eyes to feel a sense of continuity from page to page.

Lastly, the track is also a periodic button. Click and hold on the track and the content continously scrolls in that direction, a page at a time.

Tables and Columns

A common way to present data is in a table. A table in the C64 OS Toolkit consists of a scrollable area that displays rows of data divided into columns of different widths. Tables support over 65,000 rows and upto 255 columns, and are designed to draw and navigate a large number of rows quickly and efficiently.

With proper support from the Application, a table can make single line selections, multi–line selections, and discontiguous range selections. Tables support keyboard input to move the selected row, modify range selections, and scroll the visible area. With appropriate support from the Application, a table can sort and filter its contents.

A Toolkit table with vertical and horizontal scrollbars, table column headers and a range selection.

A table has a set of columns, which are displayed in a header row at the top of the table. The table's rows scroll but the column headers always stay at the top.

Columns have a title, a width and sort direction. Columns can be configured to be resizable, and can have a minium and maximum width set from 2 to 255 characters. When a column is resizable, a grippy icon is presented on the right end. The column can be resized by dragging the grippy left or right. Click on column header to sort the data by that column's criteria. An arrow icon appears before the grippy icon to indicate the direction that this column is sorted. A sorted column appears in a different color from unsorted columns. Click a sorted column header again to reverse the sort direction.

User Interface Themes

Each of the Toolkit user interface elements, described above, as well as Utility panels, the menu bar and status bar, draw themselves according to a system–wide configurable color set.

A set of colors that work well together is called a theme. C64 OS has two built–in themes: Daylight and Midnight.


Daylight is a light colored theme, with a white background. Cyan menu and status bars, light greys, and shades of blue for tabs, buttons and scrollbars.

The File Manager and the Calculator, in the Daylight color theme.
The File Manager, with the Calculator Utility, in the Daylight theme.


Midnight is a dark theme, with a black background. A higher contrast of buttons on backgrounds, greens, purples, and dark blues. Dark themes are cool and give your C64 a slick edgy look.

The File Manager and the Calculator, in the Midnight color theme.
The File Manager, with the Calculator Utility, in the Midnight theme.

The Themes Utility

You can change which theme is currently active, at anytime, using the Themes Utility. The Themes Utility can be opened from Settings, found in the Utilities menu.

Below you can see how the Themes Utility looks, presented in each of the two built–in themes. The cycle button in the bottom left allows you to cycle through the themes. When the Themes Utility is closed the system's colors are automatically updated and the selected theme is saved to settings so it remains the selected theme even after a reboot.

Themes Utility, in the Daylight Theme. Themes Utility, in the Midnight Theme.

Customize Your Theme

In addition to choosing between the built–in themes, you can use the Themes Utility to make your own custom color theme.

Click on the various user interface elements in the mockup to select the element whose color you want to customize. Your selections are saved in a third theme, called, Custom.

Themes Utility, setting up a customized color theme.

Customizable User Interface Elements

  • Screen Border
  • Screen Background
  • Utility Panel Background
  • Utility Panel Titlebar
  • Menu and Status Bar
  • Menu Highlight
  • Display Text
  • Strong Text
  • Emphasis Text
  • Selected Text (reversed)
  • Button
  • Default Button
  • Scrollbar Foreground
  • Scrollbar Background
  • Disabled Control
    (disabled menu option, button, scrollbar, etc.)
  • Text Field
  • Text Field In Focus
  • Tab Focused
  • Tab Blurred
  • Column Header Sorted
  • Column Header Unsorted

For further information about how to use the Themes Utility, see Chapter 8: Utilities.

The Clipboard

A powerful feature of C64 OS is the ability for an Application and a Utility to exchange data. While an Application and a Utility are open together they can interact with each other by passing messages. However, it is also useful for Utilities to exchange data with each other, or for one Application to exchange data with another Application. To do this the data can be copied to the clipboard as an intermediate temporary holding place.

Applications and Utilitities transfer data to the clipboard, and specify its type using C64 OS's standard data type system. The content of the clipboard persists after a Utility is quit and another is opened, while moving between Applications, and even after you leave C64 OS, power cycle your Commodore 64 and come back later.

An Application or Utility can transfer data from the clipboard at any time, but usually does this in response to your action, such as choosing paste from a menu. The application knows the data type and exact size of the content on the clipboard. Typically an Application rejects the attempt to paste data if its type is unrecognized or unsupported.

The Clipboard utility.
TODO: Replace with real screenshot

C64 OS includes a Clipboard Utility which lets you preview the current contents of the clipboard and manage up to 8 clippings. Clippings let you save common pieces of information so they can be easily pasted again in the future.

A well behaving C64 OS Application or Utility integrates well with the clipboard, allowing you to copy as many different pieces of information as possible in order to increase the probability of unintended but useful interconnections between Applications and Utilities.

Next Chapter: File System

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