Routines
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77EA: RANDOMIZE USR entry point — loading screen wait and game init
This is the address passed to RANDOMIZE USR 30698 in the BASIC loader. The loader is believed to have been: 10 LOAD "" SCREEN$ 20 LOAD "" CODE 30 RANDOMIZE USR 30698
Execution begins here with the loading screen already visible. The address has no special significance in the Spectrum architecture — it was chosen freely by the author.
Waits for a keypress on the loading screen, then fades out and draws the high-score / author credits frame (frame_hiscore_author) with the record holder name (var_record_name) printed at row 9 in red, yellow and bright. Waits for a second keypress, then resets all inventory flags, score and money, seeds the PRNG from the FRAMES counter ($5C78), and jumps into the main game loop (main_0).
Loading screen — wait for keypress
randomize_usr 77EA LD A,$00 Clear LAST K and poll until any key pressed
77EC LD ($5C08),A
77EF NOP
77F0 NOP
77F1 NOP
randomize_usr_0 77F2 LD A,($5C08)
77F5 CP $00
77F7 JR Z,randomize_usr_0
77F9 NOP NOPs (padding)
77FA NOP
77FB NOP
77FC NOP
Fade out and draw title/credits
randomize_usr_1 77FD LD A,$10 Set fade-out colour to $10, call fade_out (fade-out)
77FF LD ($C34F),A
7802 CALL fade_out
7805 LD A,$02 Border beep (OUT $FE, value 2)
7807 OUT ($FE),A
7809 LD DE,$3C00 Set CHARS=$3C00 (ROM font)
780C CALL set_chars
780F LD HL,$788D Draw high-score / author credits frame (frame_hiscore_author)
7812 CALL draw_frame
Print record holder name
7815 LD HL,$89A6 HL = name buffer (var_record_name)
7818 LD B,$20 B = 32 (unused — overwritten below)
781A LD A,$16 Emit PRINT AT control code ($16)
781C RST $10
781D LD A,$09 Row = 9
781F RST $10
7820 LD A,$00 Column = 0
7822 RST $10
7823 LD A,$11 Emit PAPER control code ($11)
7825 RST $10
7826 LD A,$02 PAPER = 2 (red)
7828 RST $10
7829 LD A,$10 Emit INK control code ($10)
782B RST $10
782C LD A,$06 INK = 6 (yellow)
782E RST $10
782F LD A,$13 Emit BRIGHT control code ($13)
7831 RST $10
7832 LD A,$01 BRIGHT = 1
7834 RST $10
7835 LD B,$20 B = 32 (character count)
randomize_usr_2 7837 PUSH BC Print loop: PUSH BC / print (HL) via RST $10 / INC HL / POP BC / DJNZ $7837
7838 LD A,(HL)
7839 RST $10
783A INC HL
783B POP BC
783C DJNZ randomize_usr_2
783E LD A,$13 BRIGHT=0
7840 RST $10
7841 LD A,$00
7843 RST $10
Title screen — wait for keypress
7844 LD A,$00 Clear LAST K and poll until any key pressed
7846 LD ($5C08),A
randomize_usr_3 7849 LD A,($5C08)
784C CP $00
784E JR Z,randomize_usr_3
7850 LD A,$01 Border beep (OUT $FE, value 1)
7852 OUT ($FE),A
7854 LD A,$00
Reset inventory and score
7856 LD ($C33D),A var_inv_gun (gun) = 0
7859 LD ($C337),A var_inv_drugs (drugs) = 0
785C LD A,$01 var_inv_wallet (wallet) = 1
785E LD ($C33C),A
7861 LD A,$30
7863 LD ($C346),A var_score_digits12 / var_score_digits34 (score) = "0000"
7866 LD ($C347),A
7869 LD ($C348),A
786C LD ($C349),A
786F LD ($C340),A var_money_digits12 / var_money_digits34 (money) = "0300" (displayed as 030000$ = 30000 escudos)
7872 LD ($C341),A
7875 LD ($C33F),A
7878 LD A,$33
787A LD ($C33E),A
Seed PRNG from hardware timer
787D LD A,($5C78) Load FRAMES counter from $5C78 into A (pseudo-random seed)
7880 SUB $80 SUB $80 — ensure A is positive
7882 LD B,A Advance PRNG (prng_tick) A times to warm up the state
randomize_usr_4 7883 PUSH BC
7884 CALL prng_tick
7887 POP BC
7888 DJNZ randomize_usr_4
788A JP main_0 Jump to main game loop (main_0)
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