 The magazine of the Melbourne PC User Group Beginners' Bytes: Part 16 Ron Wilby |
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Hi, folks, here we go again with the latest episode of "Ron's Ravings." What's new for this month? Lots of moans about Ron's troubles? No, not too much of that. Don't worry, as the sailor said when he fell from the top of the mast, I've been through lots of hardships before.
Quotable quote
Advice from Mark Trescowthick, discussing Windows. "Run as little as possible. Windows is a multitasking environment perched precariously on top of a single-tasking operating system (MS-DOS). If that sounds to you like a recipe for problems, take a bow."
Microsoft missing
Ash's editorial last month mentioned the loss of contact between user groups and Bill Gates' Mighty Microsoft Monster. Perhaps I and others have slung too much brown stuff in his direction. Perhaps he has slung too much our way. Have you ever tried to get telephone support for a Microsoft program? Its attitude is best described as contemptuous, especially to those who don't want to live in Sydney. An example is DOS 6. It was released with flaws, mainly around DoubleSpace, that caused many heartbreaks for users. Microsoft quickly produced a "fix," or was it a miss again, with DOS 6.2x? Gates has us so much under his thumb, we all had to pay $20 to get this fix for yet another Microsoft Mistake. That one should have been for free, Bill!
Nevertheless, a January Computer Age had a big spread on Mr Gates' plans, but note the piece in the corner, headed "Osborne dumps MS." Well, Osborne is Australia's third largest PC vendor, and they are loading IBM's PC DOS and OS/2 onto their new computers. These replace Microsoft's Windows and MS-DOS. Osborne says it has run out of patience with Microsoft. Today's MS DOS is little different from that of seven years ago, they say. OS/2 Warp has all the features of Windows 95 (or should that be 96?), and is available now. Remember when Windows 95 was called Chicago, and was for release late 1994? Early 96 would be a better guess now! Couple all these disasters with IBM's determined attack on Microsoft's strong market position and things could get very interesting soon.
The great RAM scam
You know about "parity bits" don't you? No, well stick around, I'll tell you. Our computers and their peripherals (means the things you hang on the back) move huge masses of information around. You can't completely avoid mistakes in transmission, so we have error detection and correction. This can get very sophisticated, especially with data transmitted for long distances over telephone lines (as with modems). But back to parity bits. Adding a parity bit is the simplest form of error detection. It doesn't reach the level of error correction at all.
Erasing every error
A data word is composed of electrical pulses, called bits, in groups of eight. These groups are called bytes. Each bit can be either high (=1) or low (=0). In parity error detection, a single (parity) bit is added to each byte. You can have even or odd parity, but let's stick with the "odd" version. This parity bit is assigned a value of one or zero so that the total number of 1s in the transmitted word is always odd (or is even in the even version). For example, if the byte to be transmitted is 10100101, the added parity bit will be 1, to give an odd number (five) of 1s in the nine-bit (8 + parity) word. Got that?
When received, each byte is checked for parity, i.e., does it have an odd number of 1s? If not, then an error is detected and the byte must be retransmitted. There is no way of telling which bit is in error, and if an even number of bit errors occur, then they won't even be detected by this simple method.
All is not what it SIMMs
What's a SIMM? Stands for Single Inline Memory Module. Used as the basic memory building block, it's just a small chip that plugs into a socket in your main board memory, video adapter memory and so on. Up till recently, your SIMMs have been 9-bit devices, the eight-bit byte plus one parity bit for error detection. So what's new? Well, some Asian manufacturers are selling us 8-bit SIMMs that contain a "parity generator." This produces a parity bit that depends on what has already been received, yes, you're right, there's no parity check at all! It's called "pseudo parity." This is a money-saving trick of course, and the amounts saved are only a few percent.
The newsletter from a large electronics organisation tells me "parity errors in memory are a rare event, virtually unknown... Disabling the parity bit can save "significant" amounts. Unfortunately, turning the page of their catalogue shows a saving of $4 on a $69 1 MB SIMM, hardly enough for me. They also suggest that "by observing a few commonsense rules you should have years of trouble-free operation." How many years?
But at the last byte (end of the day, bottom line) the decision is up to you, the customer. If you want to save a little money and you know the risks, go ahead. My gripe is, nobody is going to tell you when you are getting these cheaper modules, and you won't find much (if any) of the cost saving is passed on. Of course, if you demand 9-bit SIMMs you'll get them, but there's more.
Time delay errors
Coming from these bogus pseudo-parity SIMMs but not yet mentioned is something potentially more dangerous. Time Delay. With a true 9-bit SIMM, the parity information is available at the same time as the byte being checked. No time delay. With an 8-bit SIMM and parity generation, I'm told the delay could vary from ten to thirty nanoseconds. The last figure is nearly half a clock cycle at the most common SIMM speeds and could produce severe timing problems in your computer.
My advice! Demand the 9-pin SIMMs and keep out of trouble.
Dial Helpless (again)
What do you all read first when PC Update arrives? Half of my phone callers tell me they read Dave Mitchell first, the other half read one of my Beginners' columns. So what have we now? Back in November I was asking you all to keep to the rules regarding Dial Help. And here in Jan-Feb he is asking also. Right with you Dave, I've had three calls this morning (Sunday). I've even had people phone saying "I don't know what these rules for Dial Help are, but..." The next one who says that will be impolitely advised to go and find out! Please remember, we are all volunteers and we all have other interests, like wives, families, sleep and so on. Help us and we'll help you.
Here's a real find
Did you know DOS has a "FIND" command? You don't really need those expensive utility programs just to find something. Last week I had lost a file. Copied it to a floppy to give me hard disk space, then filed the floppy away somewhere. Suddenly I wanted that file and couldn't remember its name. FIND to the rescue.
FIND locates and displays all occurrences of a particular character string in a specified file.
There are four switches to alter the output of the command. You type
FIND [/v] [/c] [/n] [/i] "string"
followed by the name and location of the file in which to search. "string" specifies the group of characters you want to search for. Note that, in your command, you must enclose the text for "string" in quotation marks.
The switches are
- /v displays all lines not containing the specified string
- /c displays only a count of lines containing the specified string
- /n precedes each line with the file's line number
- /i makes the search non case-sensitive (capitals treated the same as small letters).
FIND /i "bak" C:\MAGFILES\BEGBYT16
This will find all occurrences of the string "bak" in either uppercase or lowercase letters in the file C:\MAGFILES\BEGBYT16. Note that DOS doesn't distinguish between capital and lowercase letters, and the /i switch ensures that FIND does likewise. You can't destroy anything with FIND, so play around and see what happens. But, take care. FIND will only work on a ASCII file. Word processor formatting symbols will defeat it every time. In the DOS 5 manual there are suggestions for some interesting uses. Have fun.
There's a new world
Since last August, I've bought and installed a DeskJet printer, which led to buying a word processor upgrade. I'm still trying to learn both of them. Having a printer with inbuilt fonts and a word processor that understands them opens a new world. My previous old dot matrix had only one font, life was simple. Now I find my screen display doing unexpected things, and it's all due to the printer font I've selected. The results I achieve, however, are more than worth all the trouble.
I also bought Windows and a mouse and they've given me a lot of new and exciting things to look forward to and learn. Then my modem arrived, that was a success with lots of help from Tony Robinson (New Users East SIG) and Gary Taig. My contributions for PC Update Jan-Feb 1995 were uploaded instead of being posted. A miracle, I wonder if I can get this month's stuff through as well. [Ed: He did! - PS] I even had a bash at the message area, and it looks like fun, but I must be doing something wrong, I never receive any messages.
I did buy the printer switch mentioned last month and it was a great success too, but now I've got video adapter problems. It intermittently produces its own set of (very strange) colours. You don't really want to hear all my troubles, so I'll see you all next month.
Cheers...
Reprinted from the March 1995 issue of PC Update, the magazine of Melbourne PC User Group, Australia
