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Having disk available is cheating --- you get to load chunks of code off disk while the game runs!

Cassette Elite had to load the entire game into RAM. It had some omissions --- fewer ships, no (or fewer?) missions, no docking computer, etc. But it was completely self contained.

Source, BTW, is available from Ian Bell's website: http://www.iancgbell.clara.net/elite/bbc/index.htm

Here's an excerpt. It's machine code using BBC Basic's built in assembler as a cheapo macro assembler:

  7000.SHPPT JSREE51:JSRPROJ:ORAK3+1:BNEnono:LDAK4:CMP#Y*2-2:BCSnono:LDY#2:jsrShpt:ldy#6:ldaK4:ADC#1:jsrShpt:LDA#8:ORAXX1+31:STAXX1+31:LDA#8:JMPLL81+2:PLA:PLA:.nono lda#&F7:andXX1+31:staXX1+31:RTS
  7010.Shpt STA(XX19),Y:iny:iny:STA(XX19),Y:LDAK3:DEY:STA(XX19),Y:ADC#3:BCSnono-2:dey:dey:STA(XX19),Y:rts
  8040.LL5 \2BSQRT Q=SQR(RQ)
  8045LDYR:LDAQ:STAS:LDX#0:STXQ:LDA#8:STAT:.LL6 CPXQ:BCCLL7:BNELL8:CPY#&40:BCCLL7:.LL8 TYA:SBC#&40:TAY:TXA:SBCQ:TAX:.LL7 ROLQ:ASLS:TYA:ROLA:TAY:TXA:ROLA:TAX:ASLS:TYA:ROLA:TAY:TXA:ROLA:TAX:DECT:BNELL6:RTS
  8065.LL28 \BFRDIV R=A*256/Q
  8070CMPQ:BCSLL2:LDX#254:STXR:.LL31 ASLA:BCSLL29:CMPQ:BCCP%+4:SBCQ:ROLR:BCSLL31:RTS:.LL29 SBCQ:SEC:ROLR:BCSLL31:RTS:.LL2 LDA#FF:STAR:RTS
  8085.LL38 \BADD(S)A=R+Q(SA)
  8090EORS:BMILL39:LDAQ:CLC:ADCR:RTS:.LL39 LDAR:SEC:SBCQ
  8095BCCP%+4:CLC:RTS:PHA:LDAS:EOR#128:STAS:PLA:EOR#255:ADC#1:RTS
  8100.LL51 \XX12=XX15.XX16
  8105LDX#0:LDY#0:.ll51 LDAXX15:STAQ:LDAXX16,X:JSRFMLTU:STAT:LDAXX15+1:EORXX16+1, X:STAS:LDAXX15+2
  8115STAQ:LDAXX16+2,X:JSRFMLTU:STAQ:LDAT:STAR:LDAXX15+3
  8120EORXX16+3,X:JSRLL38:STAT:LDAXX15+4:STAQ:LDAXX16+4,X:JSRFMLTU:STAQ:LDAT:STAR:LDAXX15+5:EORXX16+5,X
  8130JSRLL38:STAXX12,Y:LDAS:STAXX12+1,Y:INY:INY:TXA:CLC:ADC#6:TAX:CMP#17:BCCll51:RTS