Apple IIgs - Manual (Page 51)

Page 51 of 84 II gs
Printed: Thursday, July 25, 2002 12:14:50 PM
unsure about what to select, choose No Parity.
If the devices agree on odd parity as an error-checking system, the sending device adds an
extra bit set to either 0 or 1 to make the total number of bits add up to an odd number. For
example, the 7-bit ASCII code for the letter A is 1000001, which adds up to 2, an even number.
The sending device would add an extra 1 to make it odd. The receiving device adds up the bits.
If the total is odd, chances are the message is OK; if it's even, there was an error in the
transmission.
If the devices agree on even parity, the sending device adds an extra bit set to either 0 or 1
to make the total number of bits an even number.
Handshake Signals
DCD, DSR/DTR, and XON/XOFF are different protocols that a peripheral device can use to tell the
computer things like I'm ready when you're ready or Give me a second to catch my breath.
Signals that regulate the flow of data between the computer and a peripheral device are called
handshake signals.
Don't change these settings unless the manual that came with your device specifically tells you
to set them in a particular way.
DCD stands for Data Carrier Detect; DSR for Data Set Ready; and DTR for Data Terminal Ready.
XON and XOFF are ASCII charac-ters. XOFF tells the transmitting device to halt transmission of
characters. XON tells the transmitting device to resume trans-mission of characters.
RAM Disk
If you have a memory expansion card connected to your Apple IIgs, you can designate a portion
of the memory on the card to be used as a RAM disk. A RAM disk is memory that is treated like a
disk. You format it, access it by volume name, and copy or save applications and documents on
it. The advantage of using a RAM disk is that the computer can get information from it much
faster than from a disk. The disadvantage is that anything stored on the RAM disk is lost when
you turn off the power.
You don't have to designate any of the space on your memory expansion card for use as a RAM
disk (and there's no reason to with newer applications because they will take advantage of the
extra memory automatically). But experienced users, using older applications, may want to speed
up access to applications and information by using the RAM disk. This option lets you specify
the minimum and maximum amount of free RAM you want to set aside for use as a RAM disk. You
change the minimum and maximum amount of RAM you want to reserve for use as a RAM disk in
incre-ments of 32K. The minimum amount can't exceed the maximum amount. If you try to raise the
minimum above the maximum, the maximum will be automatically adjusted.
RAM disk settings don't take effect until you restart the computer by pressing Apple
key-Control-Reset.
Note: Decreasing the maximum RAM disk size won't erase what's already stored on the RAM disk.
Appendix B - Troubleshooting
Making mistakes is part of the learning process, the easy part. The hard part is figuring out
what went wrong and fixing it. That's the purpose of this appendix.
Important If the problem involves a loose connection, turn off the power and wait at least 30
seconds before connecting anything to or disconnecting anything from the computer.