The Altair 8800 panel, on one page

Sixteen switches along the bottom, and every one of them is a bit. Up is 1, down is 0. The eight on the right, A7 to A0, are the data switches: they are what DEPOSIT writes. All sixteen are the address switches: they are what EXAMINE looks at. The left eight, A15 to A8, double as the sense switches, and a program reads them with IN 377.

Addresses are read as two bytes, high then low, three octal digits each: address 000 000 is the first byte of memory and 377 377 is the last. Front panel work is done in octal because the switches are grouped in threes on the panel itself.

One byte on the eight data switches: 072 octal, which is LDA addr. Up is 1, down is 0.
D7 0	D6 0	D5 1	D4 1	D3 1	D2 0	D1 1	D0 0
2 bits → 0		3 bits → 7			3 bits → 2

So the top octal digit of a byte is never more than 3. A byte whose first digit is 4 has been misread.

The control switches

The nine control switches, left to right along the bottom row.
Up / down	What it does
OFF / ON	Down is on. Memory wakes holding a random pattern and loses it all on the way back up. It stays put.
STOP / RUN	Down runs, up stops. Only RESET works while it is running. It springs back.
SINGLE STEP / SLOW	Up runs one instruction. Down is this page’s own addition, a few instructions a second. It springs back.
EXAMINE / EXAMINE NEXT	Up shows what is at the address switches. Down moves on one address. It springs back.
DEPOSIT / DEPOSIT NEXT	Up writes the eight data switches there. Down moves on one, then writes. It springs back.
RESET / CLR	Up sends the program counter to zero. Down clears the boards in the cage. It springs back.
PROTECT / UNPROTECT	Up write-protects the board holding the address on show. Down releases it. It springs back.
AUX / AUX	Never wired to anything. The panel says so by drawing both of them black. It springs back.
AUX / AUX	Never wired either, like the one beside it. It springs back.

The lamps

The status lamps, the top left row on the panel.
Lamp	Lit when
INTE	Interrupts are enabled.
PROT	The memory on show is write-protected.
MEMR	The processor is reading memory.
INP	It is reading an input port.
M1	This is the first cycle of an instruction: the byte on the data lamps is an opcode.
OUT	It is writing to an output port.
HLTA	It has halted. Only RESET or an interrupt gets it going again.
STACK	The address on show is a stack address.
WO	Low while the processor writes. It is lit for a read, which is most of the time.
INT	An interrupt is being acknowledged.

One to try

Add two numbers: 14 bytes, address then byte, both octal.
Address	Byte	Instruction
000 000	072	LDA 0010h
000 001	020
000 002	000
000 003	107	MOV B,A
000 004	072	LDA 0011h
000 005	021
000 006	000
000 007	200	ADD B
000 010	062	STA 0012h
000 011	022
000 012	000
000 013	166	HLT
000 020	002	DB 2
000 021	002	DB 2

Putting a program in

Power on, stop the machine, then RESET.
Set the address switches to the first address and press EXAMINE.
Set the eight data switches to the first byte and press DEPOSIT.
Set the next byte and press DEPOSIT NEXT. Repeat to the end.
Then go back: first address, EXAMINE, read the data lamps against the listing, EXAMINE NEXT through the lot. MITS gave that check five of the twenty-one steps in their own loading procedure (Altair BASIC Reference Manual, 1975, Appendix A), because one wrong byte in twenty gives a program that does something else and no clue which byte.
RESET, then RUN.

All 256 bytes, and what the processor does with each

Octal, then the instruction. addr means two bytes follow, low byte first; data or port means one byte follows. A star marks the twelve encodings Intel left out of the manual that the silicon runs anyway, each an alias of the instruction beside it. Read down the columns: each one is 040 octal wide.

000 NOP	040 NOP*	100 MOV B,B	140 MOV H,B	200 ADD B	240 ANA B	300 RNZ	340 RPO
001 LXI B,addr	041 LXI H,addr	101 MOV B,C	141 MOV H,C	201 ADD C	241 ANA C	301 POP B	341 POP H
002 STAX B	042 SHLD addr	102 MOV B,D	142 MOV H,D	202 ADD D	242 ANA D	302 JNZ addr	342 JPO addr
003 INX B	043 INX H	103 MOV B,E	143 MOV H,E	203 ADD E	243 ANA E	303 JMP addr	343 XTHL
004 INR B	044 INR H	104 MOV B,H	144 MOV H,H	204 ADD H	244 ANA H	304 CNZ addr	344 CPO addr
005 DCR B	045 DCR H	105 MOV B,L	145 MOV H,L	205 ADD L	245 ANA L	305 PUSH B	345 PUSH H
006 MVI B,data	046 MVI H,data	106 MOV B,M	146 MOV H,M	206 ADD M	246 ANA M	306 ADI data	346 ANI data
007 RLC	047 DAA	107 MOV B,A	147 MOV H,A	207 ADD A	247 ANA A	307 RST 0	347 RST 4
010 NOP*	050 NOP*	110 MOV C,B	150 MOV L,B	210 ADC B	250 XRA B	310 RZ	350 RPE
011 DAD B	051 DAD H	111 MOV C,C	151 MOV L,C	211 ADC C	251 XRA C	311 RET	351 PCHL
012 LDAX B	052 LHLD addr	112 MOV C,D	152 MOV L,D	212 ADC D	252 XRA D	312 JZ addr	352 JPE addr
013 DCX B	053 DCX H	113 MOV C,E	153 MOV L,E	213 ADC E	253 XRA E	313 JMP* addr	353 XCHG
014 INR C	054 INR L	114 MOV C,H	154 MOV L,H	214 ADC H	254 XRA H	314 CZ addr	354 CPE addr
015 DCR C	055 DCR L	115 MOV C,L	155 MOV L,L	215 ADC L	255 XRA L	315 CALL addr	355 CALL* addr
016 MVI C,data	056 MVI L,data	116 MOV C,M	156 MOV L,M	216 ADC M	256 XRA M	316 ACI data	356 XRI data
017 RRC	057 CMA	117 MOV C,A	157 MOV L,A	217 ADC A	257 XRA A	317 RST 1	357 RST 5
020 NOP*	060 NOP*	120 MOV D,B	160 MOV M,B	220 SUB B	260 ORA B	320 RNC	360 RP
021 LXI D,addr	061 LXI SP,addr	121 MOV D,C	161 MOV M,C	221 SUB C	261 ORA C	321 POP D	361 POP PSW
022 STAX D	062 STA addr	122 MOV D,D	162 MOV M,D	222 SUB D	262 ORA D	322 JNC addr	362 JP addr
023 INX D	063 INX SP	123 MOV D,E	163 MOV M,E	223 SUB E	263 ORA E	323 OUT port	363 DI
024 INR D	064 INR M	124 MOV D,H	164 MOV M,H	224 SUB H	264 ORA H	324 CNC addr	364 CP addr
025 DCR D	065 DCR M	125 MOV D,L	165 MOV M,L	225 SUB L	265 ORA L	325 PUSH D	365 PUSH PSW
026 MVI D,data	066 MVI M,data	126 MOV D,M	166 HLT	226 SUB M	266 ORA M	326 SUI data	366 ORI data
027 RAL	067 STC	127 MOV D,A	167 MOV M,A	227 SUB A	267 ORA A	327 RST 2	367 RST 6
030 NOP*	070 NOP*	130 MOV E,B	170 MOV A,B	230 SBB B	270 CMP B	330 RC	370 RM
031 DAD D	071 DAD SP	131 MOV E,C	171 MOV A,C	231 SBB C	271 CMP C	331 RET*	371 SPHL
032 LDAX D	072 LDA addr	132 MOV E,D	172 MOV A,D	232 SBB D	272 CMP D	332 JC addr	372 JM addr
033 DCX D	073 DCX SP	133 MOV E,E	173 MOV A,E	233 SBB E	273 CMP E	333 IN port	373 EI
034 INR E	074 INR A	134 MOV E,H	174 MOV A,H	234 SBB H	274 CMP H	334 CC addr	374 CM addr
035 DCR E	075 DCR A	135 MOV E,L	175 MOV A,L	235 SBB L	275 CMP L	335 CALL* addr	375 CALL* addr
036 MVI E,data	076 MVI A,data	136 MOV E,M	176 MOV A,M	236 SBB M	276 CMP M	336 SBI data	376 CPI data
037 RAR	077 CMC	137 MOV E,A	177 MOV A,A	237 SBB A	277 CMP A	337 RST 3	377 RST 7

Sources

Altair 8800 Operator's Manual, Part 3: the switches, the lamps and the checking step.
Altair 8800 Assembly Manual, MITS, 1975: the panel's switch groups.
8080 CPU diagnostics: the four programs the opcode table's emulator is held to.