SWITCHES ON THE ALTAIR 8800b:

First of all, note the 16 address switches. These switches are most often
used to select memory addresses. Each switch represents one bit of the memory
location you want to address. There are 16 switches because the Altair 8800
has a 16-bit address bus, which allows it to address a maximum of 65,536
bytes of memory. (In theory, at least; However, of course, you cannot address
that much memory unless you actually have that much installed, and most
Altairs only came with 256 bytes of memory.)

POWER: The leftmost switch. This turns the unit on or off. Pretty simple,
isn't it? Brace yourself, because from here it gets less simple.

STOP / RUN: Activating RUN will run the program that is currently in memory.
Activating STOP will immediately stop the program if it is running.

SINGLE STEP / SLOW: Activating SINGLE STEP makes the program only perform the
current instruction. You can repeatedly click this to run the whole program,
one instruction at a time. SLOW works just like RUN except it makes the
program run slower so you can watch it better.

EXAMINE / EX NEXT: This switch is used to display exactly what is stored at a
particular memory address. To use it, first decide what memory address you
would like to examine, and use the 16 toggle switches to select this memory
address. For example, to examine the very first memory address, push all
the toggle switches down to select address 0. Once you have done this,
activate EXAMINE, and two interesting things will happen: First, the row of
LEDs above the 16 address switches will change. Notice they match the address
you selected; They serve to indicate exactly what address you are looking at.
The actual data is stored on the set of 8 LEDs in the upper-right. (There are
8 of them because the 8080 chip which the Altair uses has an 8-bit data bus.
This means it can send and receive a maximum of 8 bits of data (to or from
the RAM or the I/O ports) at a time. This data bus, incidentally, is what
makes the Altair considered to be "an 8-bit computer".) They will be showing
you exactly what data is stored at this particular address location. EX NEXT
is used to cycle through memory addresses; If you repeatedly activate it, the
unit will keep incrementing the address by one every time (notice that the
address LEDs change to reflect this), and the data LEDs will also change
every time to show what is being stored at this address.

DEPOSIT / DEP NEXT: After learning how the EXAMINE functions work, this
switch should be easier because it works almost the same, except that (you
guessed it) it's used to input new values into the machine, instead of simply
reading what's already there. To use it, *you must first use EXAMINE to bring
up a memory address*. The address you wish to write to must be shown on the
address LEDs. When those LEDs are showing the address you want to write to,
use the rightmost 8 address switches to set what data you want to input, then
activate DEPOSIT. Got that? When you're using EXAMINE, all 16 address
switches work to choose an address; After that, the rightmost 8 address
switches work to enter the data. After hitting DEPOSIT, the data at your
address of choice will be changed. DEP NEXT will increment the
currently-active address and then deposit the data *there*. (If you want, you
could just keep ramming DEP NEXT to fill the whole memory bank with the
current data value, one address at a time.)

RESET resets the machine.

EXT CLEAR performs an external bus reset. I have no idea what this is for,
but it has something to do with the external bus, and unless you're using a
real physical Altair, that isn't useful anyway.

PROTECT and UNPROTECT perform no function as far as I can tell other than
changing the status of the PROTECT LED.

DISPLAY / LOAD: Notice that this switch, along with INPUT / OUTPUT, is in the
"ACCUMULATOR" section of the control panel. It is used to view or set what is
in the accumulator. When you activate DISPLAY, it simply displays the
contents of the accumulator on the data LEDs in the upper-right. When you
activate LOAD, it sets the accumulator according to the rightmost 8 address
switches.

INPUT / OUTPUT: These two functions use the I/O (input/output) switches,
which are the leftmost 8 address switches. The Altair has 256 inputs and
outputs, which can be accessed by adjusting the I/O switches as appropriate.
When you activate INPUT, the accumulator is set to whatever is currently at
the selected I/O port. For example, if you have the I/O switches set to
00000010 (2), the accumulator will be set to whatever is at input 2. When you
activate OUTPUT, whatever is currently in the accumulator is sent to the
output port selected on the I/O switches.

By the way, the INTE LED means that interrupts are enabled.

Now that you know how to enter bytes into the Altair, you can start making
programs. Programs begin executing from byte 0 and just go on from there. The
Altair uses the Intel 8080 chip, so you will need to be familiar with that
chip's instruction set to program the Altair; Once you have a reference
documenting all the 8080's instructions, you can just enter in your program
into the computer and let it run.