Windows 1.0 Development Release 5

Windows 1.0 Development Release #5 is a pre-release build of Windows 1.0. This build is the fifth in the Development Release series, intended to help application developers design and develop their applications to work with Windows. As such, it contains sample apps (some of them even with source code). According to, it was compiled on 1984-11-01. It is the earliest leaked build of Windows so far.

By default, this build is installed to, with development resources in. Resources are stored in .res files outisde of the executables. The overall UI design philosophy was not developed yet, which can be seen in dialogs - some use a menu bar rather than OK and Cancel buttons.

System Requirements
According to, the following is required:

The following equipment is required: The following software is required:
 * IBM XT or AT
 * 512 K memory.
 * Floppy disk configured as DRIVE A:.
 * Hard disk configured as DRIVE C:.
 * Color graphics card.
 * External console connected to COM1: ( debugging ).
 * Microsoft mouse ( bus or serial ).
 * Timer.
 * 2.x or 3.0 MS-DOS

Installation
The installation is done with a simple batch script named. Because this build depends on an IBM XT or AT and a Bus/Serial mouse, using 86Box is recommended:

Step-by-step 1. Download PCem v0.5 (it may work with newer versions, however for example 0.7 has broken disk support) 2. Download Generic clone XT BIOS ROM 3. Extract PCem to a folder of your choice, extract pcxt.rom from genxt.zip to roms\genxt 4. Run PCem 5. Create a HDD (Disc -> Configure Hard Discs...) If you have no idea what to put in, you can use 32 sectors, 16 heads and 30 cylinders for ~8MB HDD. 6. Parition and format the HDD
 * 6.1 Insert the first floppy of DOS of your choice (tested with DOS 2.11): Disc -> Change drive A:
 * 6.2 Reboot if needed
 * 6.3 Run fdisk, choose 1, Y, press Esc twice and let it reboot
 * 6.4 Run format C: (Y, Enter)

7. Install DOS on the HDD (you can skip this step if you wish to use DOS bootdisk everytime)
 * 7.1 Run sys C:
 * 7.2 Run copy *.* C:\*.*
 * 7.3 Eject the floppy (Disc -> Eject drive A:) and reboot

8. Install Microsoft Windows 1.0 Development Release #5
 * 8.1 Insert the first floppy of your DR5 setup
 * 8.2 Run copy A:\install.bat C:\
 * 8.3 Run C:\install.bat
 * 8.4 Confirm the 4 prompts, answer Yes to any question
 * 8.5 After another confirmation, it should start copying from Disk 1 If you have the mouse captured, make sure to press CTRL+END while it's copying! Otherwise, the keypress would count as a command to continue!
 * 8.6 After it asks you, insert Disk 2, press enter (again, don't forget to uncapture your mouse)
 * 8.7 After it asks you, insert Disk 3, press enter
 * 8.8 Confirm the last prompt
 * 8.9 Eject drive A:
 * 8.10 Reboot

Now, every time you want to run Windows, run,   and   (or add it to your   file to automatically start Windows on boot).

Crash message
This build contains a warning dialog which says "Windows is about to crash". It is very hard to trigger it though, as the system will usually either hang or crash right away.

Hercules support
This version supports both CGA (640*200) & Hercules (720*348) graphics. However, only CGA drivers are installed by default. It's easy to switch from one to another, just follow these simple steps: path C:\windows\bin cd C:\windows\test drivers DesiredDriver Replace DesiredDriver with  for CGA or with   for Hercules

Registering file extensions
In the  file (in  ), you can find an   section. This is where you can register file extensions with applications. The format is as follows:

Be aware that the application has to support recieving a filename as a parameter, which Notepad doesn't at this point.

Running applications on startup
Also in  is a Run value in the   section. Any executable you include in this space-separated list gets executed before the MS-DOS Executive starts. Applications started this way go directly into iconic mode at the bottom of the screen.

References to past
If you take a look at  (in the   folder), you will see a much older date - 29/05/84. It is possible that this file was re-used from a previous build, probably from Development Release 1 which was released in 1984-05 according to InfoWorld 1984-05-07.

Also, if you take a look at the installation procedure in, you'll notice that it empties some folders, but completely removes. It's possible that previous releases used this folder, whereas DR5 uses just  instead. The batch file for uninstalling Windows,, doesn't care about  , but mentions  , so it was either modified, or the release from which it came already used.

The only reference to any previous releases in the provided documentation, in  (found in  ), where it says: "The RC.EXE program had a small file buffer. It simply couldn't handle your large menu. The bug has been repaired".

The documentation contains only one timestamp, and that is 16/10/1984 16:37 in  (also in  ). The files haven't been changed to have the same date, so you can clearly see when was each file created and modified.

References to future
In, an upcoming January release is mentioned several times: "By our January release, our goal is to..." and "In our January release, there will be...". Because the Alpha was released in 1985-01, this probably means no additional releases were made between DR5 and Alpha.

Easter Eggs, funny things
(in ) contains a "MarkTaylor" string at offset 730C. It is a default value for the DEF file if you don't specify another using /D.

The source code also contains some funny comments.

MENUID.C /* "Some people, they like to go our dancing, and other people    [like main], they do all the work . . ." */

/*   Our mad chicken-with-it's-head-cut-off error abort routine. */

PPDEMO.C /* figure out how many "characters" can fit on a line and down the screen */ /* NOTE: this routine is very stupid. These two lines get executed only */ /* once, and if the size of the window changes, it does not adjust. */

Icons
Windows 1.0 introduced the icon and cursor format (.ICO and .CUR files), though it was changed in Windows 3.0 to what it still is today. The two formats are not compatible, but files can be converted from one to the other without much work.

icon is the Superman Logo.

A bomb icon exists in, meant to be used for error messages, but neither Windows nor any included application ever displays a true error message, only warnings. The error icon was later changed to a hand doing the "stop" gesture, though the original choice of a bomb indicates early Windows development was heavily influenced by Apple's Macintosh, which also used a bomb as an error icon.

Also in  is an unused icon named , indicating older builds had a trash can feature of some kind. This is supported by photos and articles describing older builds, where this icon can be seen and is described as a place where files are discarded.

Mock-up apps
DR5 contains several mockup applications, along with their source code.