Susam's Windows Pages

Minimal Installation of WinHTTP API

2010-04-14T00:00:00Z

Here are the steps to perform for a minimal download and installation of WinHTTP API for C++ so that we have the the winhttp.lib and winhttp.h files while writing C++ programs using the WinHTTP API:

Download PSDK-x86.exe from Microsoft ® Windows Server® 2003 R2 Platform SDK Web Install.
Run the installer, select Custom installation type, clear all categories and select Microsoft Windows Core SDK > Build Environment > Build Environment (x86 32-bit).

After the installation is complete, the winhttp.h file can be found at C:\Program Files\Microsoft Platform SDK Server 2003 R2\Include.

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Character Encoding Bug in Notepad

2006-06-19T00:00:00Z

Symptoms of the Bug

I came across an interesting bug in Notepad last week. I have verified that this bug is reproducible in Windows XP. Older versions might be affected as well. Here are the steps to reproduce the issue:

Open Notepad.
Enter the following text exactly as shown here:
```
this app can break
```
Save the file.
Close Notepad.
Open the file again with Notepad.

Some users may find Chinese characters instead of the English text that was entered. Others may find 9 boxes instead.

A similar issue happens with other strings like the following ones:

Bush hid the facts

Bill hid the facts

aa aaa aaa

bb bbb bbb

We can craft many more such strings that trigger this bug if we understand what causes this bug.

Cause of the Bug

Let us take the following text as an example and try to understand what is going on:

this app can break

Here are the hexadecimal codes for the characters in the string:

74 68 69 73 20 61 70 70 20 63 61 6e 20 62 72 65 61 6b

Now let us try to interpret these 18 bytes as if they represent UTF-16LE encoded characters. After rearranging them to represent UTF-16LE encoded characters, we get 9 UTF-16LE encoded characters with the following code points:

6874 7369 6120 7070 6320 6e61 6220 6572 6b61

Click the codes above to see what the characters they represent look like. Each code represents a CJK ideograph. CJK stands for Chinese, Japanese and Korean.

We can see now that the 18 bytes entered into Notepad also happen to represent 9 valid CJK ideographs when encoded using UTF-16LE. When Notepad opens a text file, it finds that the bytes in the file happen to be valid UTF-16LE characters, so it attempts to display them as the corresponding UTF-16LE characters. Those who do not have CJK fonts installed on their systems see them appear as boxes.

Rewriting the File

One of my friends, after playing a little with this bug, asked me, "When I create that file for the first time, I see 9 boxes. But if I open the same file, delete everything, type the same thing again, close it and open it again, I don't see 9 boxes any more. I can read the English text without issues now. Does it mean that for some reason this time Notepad can interpret them as ASCII encoded characters?"

The answer is: No! In fact it is just the opposite. This time Notepad correctly saves them as UTF-16LE encoded characters.

The first time Notepad saves the data in ASCII encoding. The next time it saves it as UTF-16LE encoded characters.

Let us create the file for the first time and see what each byte looks like using the debug program of DOS.

C:\>debug foo.txt
-r ip
IP 0100
:
-d 100 11f
0B66:0100  74 68 69 73 20 61 70 70-20 63 61 6E 20 62 72 65  this app can bre
0B66:0110  61 6B BC 00 72 16 03 D3-13 C8 E8 B3 34 00 55 0B  ak..r.......4.U.
-

When we open this file using Notepad and edit, Notepad considers the text to be in UTF-16LE encoding due to reasons explained earlier in this post. Therefore it displays the text as CJK ideographs or boxes (if CJK fonts are missing). Now when we erase the text and write the same English text again, the English text is saved in UTF-16LE encoding (not ASCII encoding like the first time). This can be confirmed with the debug command.

C:\>debug a.txt
-r ip
IP 0100
:
-d 100 11f
0B66:0100  FF FE 74 00 68 00 69 00-73 00 20 00 61 00 70 00   ..t.h.i.s.  .a.p.
0B66:0110  70 00 20 00 63 00 61 00-6E 00 20 00 62 00 72 00   p. .c.a.n.  .b.r.
-

The two bytes FF and EE in the beginning is the byte order mark (BOM) for UTF-16LE encoding. The remaining bytes are the characters of the text in UTF-16LE encoding.

Read on website | #windows | #technology

WinPopup

2001-12-10T00:00:00Z

While browsing the C:\Windows directory of the Windows 98 system in our dorm room, I came across an interesting program named Winpopup.exe. It is a tiny little program that can be used to send messages from one Windows system to another on the same local area network (LAN).

Winpopup.exe in C:\Windows of Windows 98

Windows networking supports the notion of workgroups where one or more computers may logically belong to a common group. Computers belonging to the same workgroup can share resources such as files, printers, etc. with each other. To see the workgroup your computer belongs to, go to Start > Settings > Control Panel > Network > Identification and see the value of the field named "Workgroup". By default, this value is "WORKGROUP" but it can be changed to create smaller working groups of computers.

Apart from sending messages to a specific computer, WinPopup supports sending messages to an entire workgroup of computers too. An example of this is shown later in this post.

Workgroup configuration in Windows 98

To start WinPopup, go to My Computer > C: > Windows, then click on the link that says "Show Files", then scroll down to the bottom to find WinPopup.exe and finally double click on it to start it. Alternatively, you can also type win+r, type winpopup and type enter.

WinPopup running on Windows 98

To send a message, simply click on the envelope icon, select one of the radio buttons depending on whether you want to send a message to a specific computer or an entire workgroup, then type the name of the computer or workgroup you want to send your message to and then type the message to be sent.

Composing a message running on WinPopup running on Windows 98

When you are ready to send the message, just click on the OK button. If everything goes fine, a message box confirming that the message was successfully sent should appear.

Message sent successfully with WinPopup running on Windows 98

It is worth noting here that the recipient also needs to have WinPopup running in order to read messages successfully. I found this tool only a few days ago and I already find this tool to be very useful for communicating with other users of Windows systems.

Update on 30 Oct 2022: This article was imported into this website from an old intranet portal I used to run during my university days back in 2001-2005. While importing this article here, I took the liberty of adding a few screenshots taken from a Windows 98 system running in an emulator.

Read on website | #windows | #networking | #technology