Chapter 5: App Launcher

App Launcher Icon.

App Launcher is one of a pair of Applications that together are called Homebase. The other member of the pair is File Manager which is covered in Chapter 6: File Manager.

App Launcher is a desktop-like environment in which you can configure up to 5 desktops each with a backdrop image, hint color, and up to 32 aliases. Aliases can be colored and arranged however you like. Double-clicking an alias opens the corresponding Application or Utility.

If you launch into an Application from App Launcher, and then later choose to "Go Home" from that Application, you are returned to App Launcher exactly as you last left it. App Launcher is like a springboard; you bounce from it into an Application, and then return to it when you want to bounce into another Application.

Desktops and Aliases

App Launcher provides 5 customizable desktops. You are always on one of the 5 desktops, and you can switch which desktop you are currently on using the Go menu.

App Launcher's Go menu.

A checkmark appears beside the currently active desktop in the Go menu. You can use this to determine which desktop you're on. Notice that desktop has an associated keyboard shortcut. Press COMMODORE+1 through COMMODORE+5 to quickly jump to a different desktop.

Each desktop may have up to 32 aliases. If a desktop in fact had 32 aliases, it would appear quite full. This limitation is the result of screen resolution, rather than available memory.

There are 3 types of aliases:

  1. Application
  2. Utility
  3. PRG Runners

You can open an alias's corresponding item by double-clicking the alias, or by clicking it once to select it and choosing Open from the File menu, or pressing COMMODORE+O. The title of an alias directly corresponds (case-sensitively) to the filename of the item it opens. For example, if an Application alias is called "Gallery", then opening it will attempt to launch an Application named "Gallery", from the system's Application's directory (//os/applications/).

Opening a Utility alias called "Calculator" will open a Utility named "Calculator", from the system's Utilities directory (//os/utilities/). The Utility opens above App Launcher. You can even change desktops while the Utility remains open.

If a corresponding item cannot be found, the status bar displays the message, "Original Not Found."

In the example below, an alias called Missing App was double-clicked, but there is no corresponding Application whose name is "Missing App". This would most likely happen if you configured an alias to an Application or Utility that you had installed, but then subsequently uninstalled. Aliases to missing items can be scratched, renamed, or just set aside.

Status bar shows Original Not Found.

PRG Runner aliases are there to help you launch into a regular C64 program. These aliases always open the PRG Runner Utility, and that Utility uses the name of the alias to look up a corresponding PRG alias from the system's PRG aliases directory (//os/prg aliases/).

For more information about PRG Runner and PRG aliases, see Chapter 7: Utilities.

Arrange and Color

Aliases can be freely arranged by dragging them and dropping them wherever you want on the desktop. Aliases can be moved one at a time, or in groups by selecting more than one and dragging the entire selected group at the same time.

Selecting Aliases

Clicking on an aliases selects it, and unselects any and all previously selected aliases. Hold the COMMODORE key while clicking on an alias to add or remove that alias from a group selection. The number of selected aliases is displayed in the status bar.

You can also select many aliases quickly by clicking on the desktop and dragging a selection box. All the aliases that are at least partially in the selection box will be selected.

Advanced selections are possible by combining these behaviors. You can start by dragging a box around a group of aliases to select them. Then hold the COMMODORE key down and drag a box around another group of aliases to add them to the selection. Then, with the COMMODORE key still held down, you can click individual aliases to add them to the selection, or click aliases already selected to deselect them. Holding the COMMODORE key will you drag a box around aliases that are already selected deselects them. This description may sound complicated, but give it a try, it feels very natural.

Dragging a box to select several aliases.

From the Options menu you can choose "Select All" or "Select None" to select or deselect all of the aliases. An ordinary click, without the COMMODORE key held, anywhere on the desktop that is not on an alias, is also a quick way to deselect everything.

Dragging Groups of Aliases

To drag a selected group, press and hold on any selected alias, and then drag. All of the aliases will move at the same time. Their positions relative to one another are maintained. However, you cannot drag any alias such that it is wholly off the screen. If you select two aliases that are beside each other, then you drag the group from the leftmost alias towards the right side of the screen, the rightmost alias will hang at the right edge of the screen so as not to become completely lost when you drop them.

Similarly, when dragging aliases towards the top or bottom of the screen, they will hang at the bottom or top edge, so as not to get lost. In fact, if the menu bar is showing, an alias cannot be dragged under it. And if the status bar is showing, an alias cannot be dragged under it. You can hide the menu bar or status bar, and then drag an alias all to way to the top or bottom of the screen. When the menu and status bars are re-enabled, they will cover over any alias you left behind them. This can actually be kind of handy if you want merely to temporarily hide an alias that you don't want to scratch completely.

Changing Alias Colors

Each alias can be assigned any of the C64's 16 colors. Choose Colors, from the Options menu. This opens the Colors Utility. When a single alias is selected, its color is reflected automatically as the selected color in the Colors Utility. Click on any other color in the Colors Utility to change the color of the selected alias.

When the Colors Utility is in focus, you can use COMMODORE+1 through COMMODORE+8 and CONTROL+1 through CONTROL+8 to select the colors as they are labeled on the C64's keyboard.

The color of more than one alias can be configured at a time. Make a selection of aliases while the Colors Utility is open. If every alias in the selection is the same color, that color will be reflected as the selected color in the Colors Utility, otherwise, no color will be selected to indicate that the selected aliases represent more than one color. Regardless of the previous colors of the selected aliases, clicking on any color will set them all to that new color.

Setting the color of an alias.

Whenever an alias is selected, the majority of it is colored according to the system theme's selected text color. This is how you identify which aliases are selected. However, the first character of a selected alias remains in its original color. This way you can tell what color an alias is even when it's selected.

You can use colors however you please. You could color your favorites one way so they stand out from the rest. Or you could color code them so you can tell the difference between Applications, Utilities, and PRG Runners. It's entirely up to you.


Each desktop may be assigned its own backdrop file. The backdrop files are found in the system's desktop directory, //os/desktop/:X.p where X is the number from 1 to 5 for each of the 5 desktops.

Each desktop has a hint color. To set the hint color, open the Colors Utility from the Options menu. When no aliases are selected the Colors Utility sets the desktop's hint color. The hint color is shown in the screen's border. The backdrop image is composed of just two colors, the hint color for this desktop plus the theme's background color.

In the screenshots below, you can see in the status bar that no aliases are selected. As the colors are selected in the Colors Utility the hint color for the desktop is changed.

Desktop with black hint color. Desktop with blue hint color. Desktop with dark grey hint color.

What is a backdrop good for?

Backdrops can be used in any creative way that you can imagine to spice up a desktop. But here is a collection of screenshots that show a few ways that can be used, to inspire you:

Abstract repeating pattern.
Abstract repeating pattern.

An inspirational quote.
An inspirational quote.

A Logo, optionally with words.
A Logo, optionally with words.

Simple graphical image.
Simple graphical image.

Labeled boxes or sections.
Labeled boxes or sections.

Lots ot choose from, or make your own

C64 OS comes bundled with 35 stock backdrops to choose from. And you can create your own or modify the stock backdrops using the screenedit and screensave tools that come with C64 OS too.

Screenedit is a program written in BASIC and uses the screensave program to load and save the screen data very quickly. To use screenedit, quit to BASIC, change into the backdrops directory in the desktop directory, then load and run screenedit.

Without JiffyDOS:


With JiffyDOS:


It shows some help text and asks for a filename. Enter the name of an existing backdrop file, or enter a new name to create a new backdrop.

  • CONTROL+L to reload the screen from disk
  • CONTROL+Z to save the screen to disk
  • CONTROL+I to invert or reverse all characters in screen memory

After loading the first time, the image gets partially corrupted by the output of the word READY. in the top left of the screen. Just press CONTROL+L once to reload the data from disk. You now proceed to use the KERNAL ROM's built-in screen editor to draw on the screen. It has some peculiar behaviors relating to linked links and screen wrapping, so it's best if you are familiar with how to use the cursor keys and screen editor.

Colors are irrelevant, because backdrops do not retain any color information. It you want to draw an image such that the background merges with the border, it is often easiest to draw in only what you want to the screen, then use CONTROL+I to reverse everything, to see what it looks like.

Use CONTROL+Z to write the screen to the file whose name you provided at the beginning. Be careful, the cursor blinks. You may have to time your pressing of CONTROL+Z with the blinking cursor to capture it in the right phase. You can check what got saved by pressing CONTROL+L again.

PETSCII Graphics and Character Set

C64 OS runs in a modified uppercase/lowercase character set. You should do your drawing in that mode. Hold SHIFT and tap the Commodore key to toggle character sets.

From BASIC you have access to the default Character ROM, which is full of PETSCII graphical symbols. But within C64 OS those symbols are replaced by graphical UI characters and other symbols.

See Appendix II. Character Sets, to review which characters are available when in C64 OS.

The Transparent Character

One more thing to be aware of. In C64 OS, the SHIFT+SPACE (Screencode 96) is treated by the screen compositor as a transparent character. Therefore, when you're drawing, you may accidentally hold SHIFT when entering a space. It looks in the screen editor like a regular space, but as a backdrop in App Launcher it will leave holes that don't get overwritten, showing ghosts of what was previously there above it.

Changing a backdrop

To assign a new backdrop, first change to the desktop whose backdrop you want to change. Then choose Change Backdrop from the File menu, or press COMMODORE+B. From the Open Utility navigate the file system to find and select a backdrop file. Click the Select button and that file will replace the desktop's current backdrop.

Open Utility selecting a desktop backdrop.
Open Utility selecting a desktop backdrop.

After selecting a backdrop, the Open Utility remains open. You can window shade the Utility by CONTROL-clicking the title bar, or by pressing CONTROL+W. This allows you to see what the backdrop looks like, in context. And if you don't like it and want to try a different one, the Open Utility is already open.

Several sample backdrops are included with C64 OS. They are found in //os/desktop/backdrops/ as 4 block, SEQ type files, with a .p filename extension.

Saving a backdrop

In addition to changing to a new backdrop, if you like the one you're looking at on the current desktop, you can save it to a file somewhere. Choose Save Backdrop from the File menu, or press CONTROL+S.

Save Utility saving a desktop backdrop.
Save Utility saving a desktop backdrop.

Navigate to the place in the file system where you want to save the backdrop. Type a name into the Save As field, and click Save or press RETURN.

Clicking a file in the current directory puts that file's name into the Save As field. If you later navigate to another directory, the Save As field maintains its contents. When you click Save, if the specified name already exists in that directory, by default a system alert is given and the existing file is not overwritten.

To overwrite an existing file, you must enable the Allow Overwrite checkbox before clicking Save. Note: If the Allow Overwrite checkbox is checked, there will be no additional warning given when you save.

Structure of a backdrop file

The C64's screen consists of 1000 text cells, 40 columns by 25 rows. Each text cell can contain one byte, which represents one out of a set of 256 characters. In Commodore's documentation, these character index bytes are called screencodes.

An App Launcher backdrop is a SEQ type file which contains exactly 1000 bytes, interpreted as 1000 screencodes. Screencodes are not to be confused with PETSCII. Refer to the post, Commodore 64 Screen Codes, for a table of screencodes and their byte values. C64 OS does not use the standard C64 character set, though. Refer to the Appendix II. Character Sets to see the table of characters and their byte values in C64 OS.

Add New Aliases

New aliases can be added to the desktop. First change to the desktop to which you want to add a new alias. Choose Add Alias from the File menu, or press SHIFT+COMMODORE+L. From the Open Utility, navigate the file system to find and select one of three types of items:


Navigate to the system's Applications directory, //os/applications/, and select any of the currently installed Applications. Click the Select button to create an alias on the desktop to that Application.


Navigate to the system's Utilities directory, //os/utilities/, and select any of the currently installed Utilities. Click the Select button to create an alias on the desktop to that Utility.

PRG aliases

Navigate to the PRG aliases directory, //os/prg aliases/, and select any of the PRG alias files that has been previously configured with the install path and metadata for a regular C64 game or program. Click the Select button to create an alias on the desktop that will open the PRG Runner Utility with that PRG alias.

Open Utility selecting an Application.
Open Utility selecting an Application.

After clicking Select, the new alias is placed on the desktop in the top left corner with a default color. The Open Utility remains open, allowing you to add multiple aliases to the desktop without needing to reopen the Utility for each addition. Close the Utility manually when you're finished adding aliases.

If you add multiple aliases, they will be stacked on the desktop. Click and drag the topmost alias to pull it off the stack and drop it a new position. Repeat with the rest of the new aliases.


If you select a file that is not from one of these three sources, it may or may not result in an alias being created. But if one is created, it is likely that trying to open it will result in an Original Not Found error message.

Pin a Utility to the desktop

There is an alternative method to create an alias to a Utility. While any Utility is open it can be pinned to the current desktop. Choose Pin Utility from the File menu. A new alias immediately appears on the desktop that is configured to open the currently open Utility.

Scratch Aliases

Once you've created a few aliases, you may soon discover that there are a few you don't want to have anymore. Select the aliases you want to remove, and choose Scratch from the File menu.

After scratching the aliases instantaneously disappear from the desktop, but you may notice that no disk activity took place. That is because a scratched alias remains in memory but is flagged to be scratched from the disk later. If you change your mind and wish you hadn't scratched those aliases, choose Reload from the Options menu. The aliases will be reloaded from disk. Unsaved changes to the color or position of aliases will be lost.

The actual scratching of the alias files from the desktop directory happens under one of several circumstances. When you change desktop all aliases marked to be scratched are scratched for real before the new desktop is loaded in. If you try to add a new alias, but the 32 slots are already full, if at least one of those 32 slots is occupied by an alias which has been flagged for scratch, one alias will be scratched for real to make room for the new alias. Any others flagged for scratch could still be restored with a reload.

Lastly, you can choose Save from the Options menu to explicitly write out all changes to all aliases to disk.

Scratch aliases manually

Alternatively, you can use the File Manager to manually scratch aliases. See Chapter 6: File Manager → Scratch Files to learn how to scratch files. App Launcher aliases are found in //os/desktop/X/ where X is a directory whose number is 1 to 5 for each of the 5 desktops.

Move and Copy Aliases

Although you manage the aliases on any desktop by scratching the ones you don't want and adding or pinning to create a new set of aliases, this process might not be the fastest way to accomplish what you're after.

Copy aliases

You can copy one or more selected aliases from the current desktop to any other desktop. Start by selecting some aliases on the current desktop. From the File menu choose Copy To and then choose a desktop from the submenu as the destination.

When you switch to that desktop you find a copy of those aliases there. The color and position of the aliases from the original desktop are retained by the copies on their new desktop.

Move aliases

You can move one or more selected aliases from the current desktop to any other desktop. Start by selecting some aliases on the current desktop. From the File menu choose Move To and then choose a desktop from the submenu as the destination.

The aliases are first copied to the destination desktop, and then the originals on this desktop are flagged to be scratched. The color and position of the aliases on their new desktop are retained from the desktop whence they were moved.

Manage aliases manually

Alternatively, you can use the File Manager to manually move and copy aliases between desktop directories. See Chapter 6: File Manager to learn how to copy and move files. App Launcher aliases are found in //os/desktop/X/ where X is a directory whose number is 1 to 5 for each of the 5 desktops.

Some advanced tricks can be employed by using the File Manager. Here are a few examples:

  • Swap two complete desktops by swapping the desktop directory names.
  • Backup a complete desktop by copying it to another directory.
  • Maintain more than 5 desktops by swapping desktop directory names with higher numbers.
  • Assign a new backdrop by copying and naming the appropriate file to //os/desktop/.

Quit to BASIC

To leave C64 OS entirely and return to BASIC, choose Quit to BASIC from the Options menu, or press CONTROL+COMMODORE+Q.

Any unsaved changes to the current desktop are saved first.

The next time you boot C64 OS you are returned by default to the Homebase from which you quit to BASIC. So if you quit to BASIC from App Launcher, you will be returned to App Launcher when you next boot C64 OS.

Switch to File Manager

App Launcher and File Manager are two halves which form the whole known as Homebase. App Launcher is a quick and convenient way to launch Applications, Utilities and other C64 programs. And desktops can be customized with sets of aliases according to your workflow. But App Launcher is not intended to be used for managing files.

To manage files, switch to the File Manager by choosing File Manager from the Go menu. Or use the keyboard shortcut COMMODORE+F.

Next Chapter: File Manager

Table of Contents

This document is subject to revision updates.

Last modified: Sep 20, 2022