Routines
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$2241: Prepare a question and answer
This corresponds to $7A32 in the ZX Spectrum version.
Used by the routine at $0A58.
$2241 LDA $60 Pick up the current character number from $60.
$2243 CMP #$0B Is it $0B (MR WACKER)?
$2245 BEQ $224A Branch if so.
$2247 JMP $22F3 Otherwise jump forward.
MR WACKER is conducting this lesson, so we have to prepare a multiplication question and answer. First, generate two random numbers and store the ASCII codes of their digits in the question message.
$224A LDX #$20 Generate a random number between 32 and 99 and store it at $A3 and $C0.
$224C LDY #$63
$224E JSR $253E
$2251 STA $A3
$2253 STA $C0
$2255 LDA #$30 Store the code for '0' at $8B for no apparent reason.
$2257 STA $8B
$2259 JSR $221C Generate the character codes of the digits of this number at $8D and $8E.
$225C LDA #$00 Store $5A00 (WHAT IS 12 x 34?) at $50.
$225E STA $50
$2260 LDA #$5A
$2262 STA $51
$2264 LDY #$08 Replace the '12' in this message with the digits of the number.
$2266 LDA $8D
$2268 STA ($50),Y
$226A INY
$226B LDA $8E
$226D STA ($50),Y
$226F LDX #$20 Generate another random number between 32 and 99 and store it at $A3 and $C1.
$2271 LDY #$63
$2273 JSR $253E
$2276 STA $A3
$2278 STA $C1
$227A LDA #$30 Store the code for '0' at $8B for no apparent reason.
$227C STA $8B
$227E JSR $221C Generate the character codes of the digits of this number at $8D and $8E.
$2281 LDY #$0D Replace the '34' in the question message with the digits of the number.
$2283 LDA $8D
$2285 STA ($50),Y
$2287 INY
$2288 LDA $8E
$228A STA ($50),Y
$228C LDY #$08 Multiply the two numbers and store the product at $A3 and $A4.
$228E LDA #$00
$2290 ASL A
$2291 ROL $C0
$2293 BCC $229C
$2295 CLC
$2296 ADC $C1
$2298 BCC $229C
$229A INC $C0
$229C DEY
$229D BNE $2290
$229F STA $A3
$22A1 LDA $C0
$22A3 STA $A4
$22A5 JSR $217E Generate the character codes of the digits of this product.
$22A8 LDA #$11 Store $5A11 (Please Sir I cannot tell a lie . . It's 1234) at $52.
$22AA STA $52
$22AC LDA #$5A
$22AE STA $53
$22B0 LDY #$06 Replace the '1234' in this message with the digits of the answer to the multiplication question.
$22B2 LDA $8B
$22B4 STA ($52),Y
$22B6 INY
$22B7 LDA $8C
$22B9 STA ($52),Y
$22BB INY
$22BC LDA $8D
$22BE STA ($52),Y
$22C0 INY
$22C1 LDA $8E
$22C3 STA ($52),Y
$22C5 LDA $60 Pick up the teacher's character number from $60.
$22C7 PHA Save it temporarily.
$22C8 LDA #$11 Set the current character number at $60 to $11 (EINSTEIN).
$22CA STA $60
$22CC JSR $3279 Copy EINSTEIN's character buffer to page 0.
$22CF LDA $52 Copy the address of the answer message into EINSTEIN's character buffer.
$22D1 STA $AC
$22D3 LDA $53
$22D5 STA $AD
$22D7 JSR $33BF Restore EINSTEIN's buffer from page 0.
$22DA PLA Restore the teacher's character number to A.
$22DB STA $60 Update the current character number at $60.
$22DD JSR $3279 Copy the teacher's character buffer to page 0.
$22E0 LDA $50 Copy the address of the question message into the teacher's buffer.
$22E2 STA $AC
$22E4 LDA $51
$22E6 STA $AD
$22E8 LDA #$87 Place the address of the interruptible subcommand routine at $2387 into the teacher's buffer to make him ask the question.
$22EA STA $AA
$22EC LDA #$23
$22EE STA $AB
$22F0 JMP $2386 Return.
Some teacher other than MR WACKER is conducting this lesson. Check whether MR CREAK needs to ask what happened in the year that he was born.
$22F3 CMP #$0E Is the current character number $0E (MR CREAK)?
$22F5 BNE $2320 Branch if not.
$22F7 LDA $46 Pick up the game mode indicator from $46.
$22F9 BEQ $2320 Branch if we're in demo mode.
$22FB CMP #$03 Has ERIC already opened the safe?
$22FD BCS $2320 Branch if so.
$22FF LDA $C2 Has MR CREAK already asked the birth year question in this lesson?
$2301 BNE $2320 Branch if so.
$2303 LDA #$01 Update the birth year question indicator at $C2.
$2305 STA $C2
$2307 LDA #$2D Store $5B2D (WHAT HAPPENED IN THE YEAR THAT I WAS BORN) at $50.
$2309 STA $50
$230B LDA #$5B
$230D STA $51
$230F LDA #$E1 Store $5AE1 (Please Sir I cannot tell a lie . . It was the BATTLE OF Q) at $52.
$2311 STA $52
$2313 LDA #$5A
$2315 STA $53
$2317 LDY #$16 Replace the 'Q' in this message with the message number of MR CREAK's year of birth.
$2319 LDA $A5
$231B STA ($52),Y
$231D JMP $22C5 Jump back to prepare MR CREAK and EINSTEIN.
Now we randomly select a question-answer pair.
$2320 LDX #$00 Generate a random value between $00 and $29 and store it at $57.
$2322 LDY #$29
$2324 JSR $253E
$2327 STA $57
$2329 LDA $60 Pick up the current character number from $60.
$232B CMP #$0C Is it $0C (MR ROCKITT)?
$232D BEQ $2338 Branch if so.
$232F CMP #$0D Is the current character number $0D (MR WITHIT)?
$2331 BEQ $233D Branch if so.
$2333 LDA #$D4 The history message numbers are in the range $D4-$FD.
$2335 JMP $233F Jump forward.
$2338 LDA #$80 The chemistry message numbers are in the range $80-$A9.
$233A JMP $233F Jump forward.
$233D LDA #$AA The geography message numbers are in the range $AA-$D3.
$233F CLC Add the random value between $00 and $29 chosen earlier to the base message number, and store the result at $C3.
$2340 ADC $57
$2342 STA $C3
$2344 LDA $60 Pick up the teacher's character number ($0C-$0E) from $60.
$2346 SEC Change it to 0 (MR ROCKITT), 4 (MR WITHIT) or 8 (MR CREAK), and store it at $57.
$2347 SBC #$0C
$2349 ASL A
$234A ASL A
$234B STA $57
$234D LDA $C3 Pick up the message number from $C3.
$234F LSR A Is the message number even?
$2350 BCC $2359 Branch if so.
$2352 LDA $57 Add 12 to the teacher identifier at $57, giving 12 (MR ROCKITT), 16 (MR WITHIT) or 20 (MR CREAK).
$2354 CLC
$2355 ADC #$0C
$2357 STA $57
$2359 LDA $57 Pick up the LSB of the address of the question message from the data table at $46E0 and copy it to $50.
$235B TAX
$235C LDA $46E0,X
$235F STA $50
$2361 LDA #$5A Set the MSB of the address of the question message to $5A.
$2363 STA $51
$2365 INX Replace the 'Q' in the question message with the randomly chosen message number saved at $C3.
$2366 LDA $46E0,X
$2369 TAY
$236A LDA $C3
$236C STA ($50),Y
$236E INX Pick up the LSB of the address of the answer message from the data table at $46E0 and copy it to $52.
$236F LDA $46E0,X
$2372 STA $52
$2374 LDA #$5A Set the MSB of the address of the question message to $5A.
$2376 STA $53
$2378 INX Replace the 'Q' in the answer message with the appropriate message number.
$2379 LDA $46E0,X
$237C TAY
$237D LDA $C3
$237F EOR #$01
$2381 STA ($52),Y
$2383 JMP $22C5 Jump back to prepare the teacher and EINSTEIN.
$2386 RTS
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