CP/M/CPM_CDROM.iso/lambda/soundpot/f/nbasic.lbr/NBASIC2.DZC/NBASIC2.DOC

Text File | 1993-10-26 | 14.5 KB | 382 lines

NBASIC2.DOC

                 NBASIC║ ┴ STRUCTURE─ PREPROCESSO╥ FO╥ MBASIC
                               b∙ Nami≥ Shammas
                         witΦ expansion by m. w. hulse


NBASIC¼áá ┴áá preprocesso≥á fo≥á MBASI├á anΣá BASICA¬á programs¼áá ¬áá - BASIC┴ ì
compatibilit∙á no⌠ testeΣ afte≥ m∙ changes-mΦ offer≤ ne≈ command≤ anΣá feature≤ ì
t∩ programmers« Thesσ feature≤ are:

     ∩ Thσ usσ oµ alphanumeriπ label≤ iε branching.
     ∩ Thσ REPEAT-UNTI╠ loop.
     ∩ Thσ CASE-O╞ structurσ fo≥ multiwa∙ I╞ statements.
     ∩ Fortran-likσ subroutinσ calls.

Thesσ feature≤ mainl∙ enablσ thσ programme≥ t∩ avoiΣ thσ usσ oµ linσ number≤ iε ì
branchinτá operations«á Thi≤á  mean≤á program≤á caε no≈ bσ writteεá iεá ßá morσ ì
structureΣá way«á Thσ rolσ oµ NBASI├ i≤ t∩ proces≤ thesσ program≤á anΣá conver⌠ ì
theφ iε t∩ synta° accepteΣ b∙ thσ BASI├ interpreter.

NBASI├ doe≤ no⌠ havσ extensivσ erro≥ checking╗ i⌠ keep≤ thσ amoun⌠ oµ codσ t∩ ß ì
minimuφ iε orde≥ t∩ maximizσ thσ numbe≥ oµ line≤ i⌠ caε process.

                                 NBASI├ LABELS

Fou≥ olΣ keyword≤ ma∙ bσ useΣ witΦ NBASI├ labels« The∙ are:

     ∩ GOTO(label⌐
     ∩ GOSUB(label)
     ∩ THEN(label)
     ∩ ELSE(label)

          ┴ labe∞ i≤ defineΣ witΦ thσ form:

               [LBL:label]

Al∞ space≤ arσ significan⌠ withiε squarσ brackets«á A≤ aε example¼ iµ NBASI├ i≤ ì
giveε thi≤ program:


          1░ [LBL:START▌ INPU╘ "ENTE╥ ╪ ";X   Note "LBL: used here
          2░ I╞ ╪ <=░ THE╬ [QUIT]             but not here
          3░ PRIN╘ "╪ ╜ ";X
          4░ X=X+1
          5░ I╞ X>░ THE╬ [START]              or here.
          6░ [LBL:QUIT▌ END                   Used here.

¬ - BASIC┴ compatibilit∙ no⌠ testeΣ afte≥ m∙ changes-mh
--------------------
Copyrigh⌠ 198│ b∙ Nami≥ Clemen⌠ Shamma≤ anΣ 198┤ b∙ Merril∞ Williaφ Hulse«á Al∞ ì
right≤ reserved« Permissioε i≤ granteΣ fo≥ non-commercia∞ usσ anΣ distribution« ì
Commercia∞ usσ withou⌠ thσ author'≤ writteε permissioε i≤ forbidden«á PublisheΣ ì
iε Dr« Dobb≤ Journal¼ Januar∙ 1984.

è                                       1










     it wil∞ producσ thi≤ output:

          1░ INPU╘ "ENTE╥ ╪ ";X
          2░ I╞ ╪ <=░ GOT╧ 60
          3░ PRIN╘ "╪ ╜ ";X
          4░ X=X-1
          5░ I╞ X>░ GOT╧ 10
          6░ END

Label≤ ma∙ bσ useΣ morσ thaε oncσ oε thσ samσ line¼ a≤ in:

          I╞ X>░ THE╬ [MOVE▌ ELS┼ [QUIT]

┴ labe∞ ma∙ bσ defineΣ anywherσ oε ß line¼ a≤ lonτ a≤ thσ definitioε i≤ no⌠ thσ ì
las⌠ iteφ oε tha⌠ line« ┴ labe∞ definition¼ however¼ shoulΣ no⌠ appea≥ alonσ oε ì
ß line╗ a⌠ leas⌠ onσ remarδ shoulΣ follo≈ it:

          10░ [LBL:HERE▌ 'remarδ appended

                            THE "REPEAT-UNTI╠" LOOP

Thσá REPEAT-UNTI╠ structurσ allow≤ ß prograφ t∩ g∩ througΦ ß blocδ oµá command≤ ì
a⌠á leas⌠ oncσ anΣ theε t∩ tes⌠ whethe≥ ß repea⌠ i≤ needed«á Thσ genera∞á usagσ ì
is║

          REPEAT
               statements
          UNTI╠ (test)

Thesσá loop≤ ma∙ bσ nested«á Thσ variable≤ I1¼á I2¼á anΣ s∩ oε arσ reserveΣ fo≥ ì
loo≡á contro∞ anΣ shoulΣ no⌠ bσ useΣ withiε thσ REPEAT-UNTI╠ loop«á Herσá i≤á ß ì
sample:

          1░ INPU╘ "ENTE╥ ╪ ";X
          2░ REPEAT
          3░ PRIN╘ "╪ ╜ ";X
          4░ X=X-1
          5░ UNTI╠ (X>=0)
          6░ END

Froφ tha⌠ program¼ NBASI├ wil∞ produce:

          1░ INPU╘ "ENTE╥ ╪ ";X
          2░ FO╥ I1=░ T╧ 1:'REPEAT
è          3░ PRIN╘ "╪ ╜ ";X
          4░ X=X-1
          5░ I1=-1*(X>=0):NEX╘ I▒ :'UNTI╠ (X>=0⌐
          6░ END

Thσá REPEA╘á keyworΣ ma∙ bσ precedeΣ b∙ aε NBASI├ label«á Otherwise¼á botΦá thσ ì
REPEA╘á anΣá UNTI╠á keyword≤ shoulΣ bσ alonσ oεá thei≥á lines╗á nothinτá shoulΣ ì
precedσ o≥ follo≈ them.



                                       2










                            THE "CASE-O╞" STRUCTURE

Thσá CASE-O╞ Structurσ allow≤ multiple¼á multilinσ I╞ statements«á It≤á genera∞ ì
forφ is:

          CAS┼ O╞ (expressioε 0)
          !(expressioε 1)DO
               statemen⌠ grou≡ 1
          !(expressioε 2)DO
               statemen⌠ grou≡ 2
          ELS┼ DO
               defaul⌠ statements
          ENDCASE

Thσá CASE-O╞á commanΣá tes⌠ thσ valuσ oµ expressioεá ░á agains⌠á expressioεá 1¼ ì
expressioεá 2¼á anΣá s∩ forth¼á anΣ execute≤ onl∙ thσ grou≡ oµ statement≤á tha⌠ ì
correspond≤ t∩ ß successfu∞ test«á Thσ !ELS┼ D╧ i≤ offereΣ a≤ ß "wheε al∞á elsσ ì
fails,do...ó option« Herσ i≤ aε example:

          1░ INPU╘ "ENTE╥ ╪ ";X
          2░ CAS┼ O╞ (X)
          3░ !(0⌐ DO
          4░ PRIN╘ "╪ I╙ 0"
          5░ !(1⌐ DO
          6░ PRIN╘ "╪ I╙ 1"
          7░ !ELS┼ DO
          8░ PRIN╘ "SOMETHIN╟ ELSE"
          9░ ENDCASE
          10░ END

Froφ that¼ NBASI├ wil∞ produce:

          1░ INPU╘ "ENTE╥ ╪ ";X
è          2░ I0=(X)
          3░ I╞ I0<>(0⌐ THE╬ 50
          4░ PRIN╘ "╪ I╙ 0"
          5░ I╞ I0<>(1⌐ THE╬ 70
          6░ PRIN╘ "╪ I╙ 1"
          7░ DUMY=1'Dumm∙ statement
          8░ PRIN╘ "SOMETHIN╟ ELSE"
          9░ DUMY=1'Dum∙ statement
          10░ END

┴ CASE-O╞ structurσ ma∙ havσ u≡ t∩ fift∙ statemen⌠ blocks« NBASI├ label≤ ma∙ bσ ì
useΣ anywherσ iε thσ blocks¼ bu⌠ thσ structure≤ ma∙ no⌠ bσ nested« N∩ morσ thaε ì
onσ !ELS┼ D╧ linσ shoulΣ appea≥ iε an∙ CASE.

                               SUBROUTINE CALLS

AlthougΦáá thσá NBASI├á subroutinσá featurσá simulate≤á Fortraεáá  calls¼áá thσ ì
subroutine≤á arσá actuall∙á par⌠á oµ thσ maiε prograφ anΣ ma∙á no⌠á havσá loca∞ ì
variables.



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Aε NBASI├ subroutinσ begin≤ witΦ ß SU┬ statemen⌠ iε thi≤ form:

          SU┬ "nameó TAKE╙ input-list GIVE╙ result-list

Thσá keyworΣá SU┬á introduce≤ thσ linσ anΣ thσ namσ iεá quote≤á identifie≤á thσ ì
subroutine≤á fo≥á usσá iε ß cal∞ statement«á Thσ TAKE╙ anΣá GIVE╙á clause≤á arσ ì
optional╗á the∙ definσ thσ interfacσ t∩ thσ subroutine«á Thσ 'input-listº i≤á ß ì
lis⌠á oµá variablσ name≤ througΦ whicΦ thσ subroutinσ receive≤ it≤á input«á Thσ ì
'result-listºá i≤ ß lis⌠ oµ variablσ name≤ tha⌠ wil∞ contaiε thσá result≤á wheε ì
thσ subroutinσ ends« Herσ arσ somσ example≤ oµ subroutinσ declarations║

     ∩ SU┬ "TESTó TAKE╙ A;B;├ GIVE╙ E
     ∩ SU┬ "MATRIXó TAKE╙ A(1,I⌐ GIVE╙ B(J)
     ∩ SU┬ "TRY"
     ∩ SU┬ "ROOTó GIVE╙ FOFX

┴ subroutinσ end≤ witΦ ß returε statement.

Thσ CAL╠ statemen⌠ i≤ useΣ t∩ cal∞ ß subroutine« Thσ TAKE╙ anΣ GIVE╙ clause≤ iε ì
thσá CAL╠á statemen⌠á arσá matcheΣá u≡ witΦ thσá samσá clause≤á iεá thσá calleΣ ì
subroutine«á Thσ variablσ name≤ arσ matcheΣ b∙ position╗ the∙ d∩ no⌠ havσ t∩ bσ ì
exactl∙á thσ samσ iε thσ CAL╠ anΣ SU┬ statements«á NBASI├ generate≤á assignmen⌠ ìèstatement≤á t∩ cop∙ thσ caller'≤ TAKE╙ variable≤ int∩ thσ subroutine'≤á anΣá t∩ ì
cop∙á thσá subroutine'≤ GIVE╙ variable≤ int∩ thσá caller's«á Fo≥á example║á thσ ì
program:

     1░ INPU╘ "ENTE╥ ╪ ";X
     2░ CAL╠ "TES╘ TAKE╙ ╪ GIVE╙ X;Z
     3░ PRIN╘ Y
     4░ PRIN╘ Z
     5░ END
     6░ SU┬ "TESTó TAKE╙ ┴ GIVE╙ B(1);B(2)
     7░ B(1)=A*A
     8░ B(2)=SQR(A)
     9░ RETURN

wil∞ bσ converteΣ b∙ NBASI├ to:

     1░ INPU╘ "ENTE╥ ╪ ";X
     2░ A=X:GOSU┬ 60║ Y=B(1):Z=B(2)
     3░ PRIN╘ Y
     4░ PRIN╘ Z
     5░ END
     6░ 'SU┬ "TESTó TAKE╙ ┴ GIVE╙ B(1);B(2)
     7░ B(1)=A*A
     8░ B(2)=SQR(A)
     9░ RETURN

Subroutinσá call≤ ma∙ bσ nesteΣ a≤ lonτ a≤ thσ variablσ name≤á don'⌠á conflict« ì
Recursion¼á however¼á i≤ no⌠ allowed« Thσ CAL╠ anΣ SU┬ statement≤ mus⌠ bσ alonσ ì
oε thei≥ lines╗ nothinτ shoulΣ precedσ o≥ follo≈ them« ┴ blanδ mus⌠ comσ beforσ ì
AnΣ afte≥ thσ keyword≤ TAKE╙ anΣ GIVES.



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                                 USING NBASIC

NBASIC.BA╙ i≤ ß BASI├ program«á NBASIC.CO═ i≤ als∩ available«á T∩ usσ i⌠á firs⌠ ì
develo≡á thσá prograφá usinτá you≥ edito≥ o≥ worΣ processo≥á modulσá b∙á modulσ ì
startinτá witΦá thσá contro∞á modulσ anΣá addinτá module≤á anΣá subroutine≤á a≤ ì
appropriate«á Don'⌠á usσá linσá number≤á anΣ kee≡ eacΦ prograφá linσá withiεá ß ì
physica∞ linσ (e« g« unde≥ 8░ columns)¼ iµ possible« Iµ yo⌡ don't¼ remembe≥ thσ ì
linσ positioε fo≥ late≥ adjustment« Movσ module≤ arrounΣ a≤ needeΣ t∩ establisΦ ì
ßá logica∞á prograφ flo≈ witΦ commoε subroutine≤ groupeΣ togethe≥á anΣá specia∞ ì
subroutine≤á groupeΣá iεá aε orde≥ tha⌠ make≤ sensσá t∩á you«á Tr∙á t∩á reservσ ì
"GOTO/THEN/ELS┼á linenumberó fo≥ in-a-single-linσ loop≤ return≤ t∩ re-display ß ìèuse≥á questioεá afte≥ aε erro≥ o≥ a≤ par⌠ oµ ß  qualifie≥ fo≥  skipinτá ove≥á ß ì
modulσá t∩á thσá nex⌠ module«á Wheε yo⌡ arσ donσ witΦ thσ prograφá o≥á ßá majo≥ ì
segment¼ savσ thσ prograφ a≤ aε ASCI╔ filσ (i.e« SAV┼ "d:filename",A).

Nex⌠á preparσá thσá prograφ o≥ segmen⌠ fo≥ tes⌠ b∙ runninτ PI╨á witΦá thσá linσ ì
numberinτ optioε "Nó  e«á g«á A>PI╨ B:URPROG=B:URPROG[N]«á "PRINTó thσ filσá iε ì
CP/═á t∩á seσ iµ yo⌡ haΣ an∙ lonτ line≤ (ove≥ 8░ characters)«á Iµ yo⌡ diΣá run¼ ì
you≥á edito≥ t∩ adjus⌠ linσ numbers«á  Theε loaΣ NBASI├ anΣ RU╬ it«á Iµá NBASI├ ì
detect≤á  error≤ i⌠ wil∞ displa∙ anΣ optionall∙ prin⌠ a⌠ leas⌠ somσ oµ theφ anΣ ì
hal⌠ withou⌠ savinτ thσ result«á Afte≥ yo⌡ havσ correcteΣ thσ error≤ displayed¼ ì
ruε again«á  Wheε n∩ error≤ arσ detected¼á thσ converteΣ prograφ wil∞ bσ saved¼ ì
listeΣ anΣ optionall∙ printeΣ anΣ it≤ filenamσ wil∞ bσ displayed.

Notσá tha⌠á iµ yo⌡ inpu⌠ ß filσ witΦ .BA╙ a≤ thσ filσ typσ i≤ ".BAZó s∩á a≤á t∩ ì
separatσá thσ NBASI├ sourcσ codσ froφ thσ BASI├ "objectóá code«á Thσá converteΣ ì
prograφá i≤á als∩ iε ASCI╔ form╗á afte≥ changinτ it≤ filσ typσ anΣá thσá NBASI├ ì
sourcσ filσ name¼ yo⌡ caε loaΣ i⌠ anΣ eithe≥ edi⌠ i⌠ o≥ ruε it« Yo⌡ ma∙ wan⌠ t∩ ì
adjus⌠ it≤ indentatioε o≥ changσ thσ generateΣ code.

Iµ yo⌡ successfull∙ completσ testinτ oµ ß segmen⌠ oµ ß large≥ program¼á yo⌡ caε ì
adΣá i⌠á int∩  aε NBASI├ sourcσ prograφ b∙  editinτ thσ segmen⌠ filσ t∩á removσ ì
thσá linσá number≤ (usσ column-block-deletσ iµ yo⌡ havσ it.⌐ anΣ theεá reaΣá i⌠ ì
int∩á thσ prope≥ placσ iε thσ NBASI├ program«á Wheε thσ wholσ prograφ i≤á done¼ ì
ruε i⌠ al∞ througΦ NBASIC as described above«

                             HOW THE PROGRAM WORKS

Thσ accompanyinτ NBASI├ prograφ function≤ iε thσ followinτ way.

Linσ 1040 set≤ thσ dimension≤ (whicΦ ma∙ bσ altered¼ memor∙ permitting⌐ fo≥ thσ ì
numbe≥ oµ line≤ anΣ othe≥ parameters.

Thσá line≤ a⌠ 110░ obtaiε thσ prograφ filσ namσ anΣ reaΣ thσ filσ t∩ thσ strinτ ì
arra∙á L$(I⌐ whilσ countinτ thσ numbe≥ oµ line≤ read«á Thσ LIN┼á INPU╘á commanΣ ì
ensure≤ tha⌠ line≤ containinτ comma≤ arσ no⌠ interpreteΣ a≤ severa∞ strings«

Thσ loo≡ a⌠ linσ 200░ convert≤ an∙ RE═ int∩ thσ apostrophσ tha⌠ serve≤ thσ samσ ì
purpose╗ i⌠ i≤ easie≥ t∩ handlσ onl∙ onσ remarδ symbol.

Thσ REPEAT-UNTI╠ featurσ i≤ handleΣ a⌠ linσ 3000«á NBASI├ searche≤ eacΦ prograφ ì
linσá fo≥á thσ token≤ REPEA╘ anΣ UNTIL«á Thσ variablσ CNT¼á whicΦ serve≤á a≤á ß ì
recorΣá keeper¼á i≤á incrementeΣá b∙á onσá fo≥ ever∙á REPEA╘á tokeεá founΣá anΣ ì
decrementeΣ b∙ onσ fo≥ eacΦ UNTI╠ token« CN╘ monitor≤ thσ prope≥ sequencinτ anΣ

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ìèmatchinτ oµ thσ tw∩ token≤ anΣ allow≤ nesteΣ loops« thσ REPEA╘ i≤ replaceΣ b∙ ß ì
FO╥á statemen⌠ anΣ it≤ correspondinτ NEX╘ statemen⌠ replace≤ thσá UNTI╠á token« ì
Thσá tes⌠á expressioε tha⌠ wa≤ originall∙ witΦ thσ UNTI╠ tokeε i≤á incorporateΣ ì
int∩ ß statemen⌠ affectinτ thσ valuσ thσ valuσ oµ thσ loo≡ counte≥ prio≥ t∩ it≤ ì
NEX╘á statement«á Iµ thσ tes⌠ fails¼á thσ loo≡ counte≥ i≤ se⌠ t∩ zer∩ s∩ a≤á t∩ ì
repea⌠ thσ loop«á Otherwise¼á i⌠ i≤ se⌠ t∩ onσ t∩ exi⌠ thσ loop«á Thσ Line≤á a⌠ ì
400░á conver⌠á thσá alphanumeriπ label≤ int∩ thσ actua∞ linσ number≤á the∙á arσ ì
associateΣá with«á Iεá thσ loo≡ residinτ a⌠ linσ 5000¼á thσ prograφá scan≤á thσ ì
entirσá use≥ prograφ fo≥ alphanumeriπ label≤ storinτ whateve≥ label≤ arσá founΣ ì
iεá thσá strinτ arra∙ LBLñ anΣ thσ correspondinτ linσ number≤á iεá LSTK¼á whilσ ì
removinτá thσ label≤ froφ thσ line«á Iµ thσ labe∞ i≤ alonσ iε ß line¼á thσ linσ ì
wil∞á bσ reduceΣ t∩ nothing¼á whicΦ i≤ wh∙ aε alphß labe∞ linσá shoulΣá contaiε ì
additiona∞ text¼á a⌠ leas⌠ ß remarkí Thσ loo≡ a⌠ linσ 600░ scan≤ fo≥ thσ NBASI├ ì
tokeεá word≤ useΣ witΦ alphanumeriπ labels¼á makinτ surσ tha⌠ thσ alphßá label≤ ì
mentioneΣ iε thesσ token≤ arσ valid«

Thσá CASE-O╞ featurσ i≤ handleΣ a⌠ linσ 7000«á Herσ NBASI├ scan≤ fo≥ thσá tokeε ì
worΣá CAS┼á O╞á anΣá expect≤á t∩ finΣ   aεá ENDCAS┼á tokeεá anΣá a⌠á leas⌠á onσ ì
!(expression)« Thσ locatioε anΣ presencσ oµ thσ optiona∞ !ELS┼ D╧ tokeε anΣ thσ ì
numbe≥ oµ expressions¼á thei≥ location≤ anΣ thσ presencσ  anΣ  arσ monitored« ┴ ì
GOT╧á thσ forme≥ ENDCAS┼ linσ i≤ inserteΣ a⌠ thσ enΣ oµ eacΦ casσ optioε block« ì
Thσá ELS┼á D╧á anΣá ENDCAS┼ token≤ arσá transformeΣá int∩á remarks¼á whilσá thσ ì
!(expression⌐ statement≤ arσ turneΣ int∩ I╞ statements«á NBASI├ deal≤ witΦá thσ ì
CAS┼á O╞á featurσá oεá ßá "case-by-caseó basis¼á thu≤ n∩á nestinτá oµá CAS┼á O╞ ì
statement≤ i≤ allowed.

Linσá 800░ tackle≤ thσ CAL╠ feature«á Again¼á NBASI├ scan≤ thσá entirσá prograφ ì
searchinτ fo≥ thσ SU┬ token«á Wheε onσ i≤ founΣ thσ prograφ studie≤ thσ linσ t∩ ì
extrac⌠ thσ subroutinσ namσ anΣ thσ input/outpu⌠ variablσ lists« Fo≥ thσ latte≥ ì
lists¼ thσ prograφ test≤ thei≥ presence¼ count≤ thσ numbe≥ oµ variable≤ iε eacΦ ì
lis⌠á anΣá learn≤á thei≥á names«á Thσ synta° oµ thσ lis⌠á relie≤á onl∙á oεá thσ ì
semicolon¼á s∩á a≤ t∩ avoiΣ confusioε wheε botΦ array≤ anΣ expression≤ arσ useΣ ì
iε thσ lists«á Thσ name≤ oµ thσ variable≤ iε thσ input/outpu⌠ list≤ arσá storeΣ ì
iε thσ strinτ NM$«á T∩ kee≡ memor∙ requirement≤ a⌠ ß minimum¼ oncσ ß subroutinσ ì
i≤ declared¼á NBASI├ scan≤ thσ entirσ use≥ prograφ t∩ conver⌠ an∙ call≤ t∩ tha⌠ ì
subroutine.

Iε thσ loo≡ residinτ a⌠ linσ 9000¼á thσ prograφ start≤ t∩ scaε thσ use≥ prograφ ì
fo≥á subroutinσ CALLs«á Herσ thσ prograφ studie≤ thσ CAL╠ statemen⌠ t∩ matcΦ i⌠ ì
witΦ thσ subroutinσ namσ tha⌠ i≤ declared«á Thσ input/outpu⌠ variablσ list≤ arσ ì
examineΣ (iµ available⌐ anΣ ß replacemen⌠ line¼á storeΣ iε L$¼á i≤á formed╗á i⌠ ì
contain≤ thσ linσ numbe≥ wherσ thσ subroutinσ cal∞ wa≤ originateΣ anΣ thσ GOSU┬ ì
statement«á Thσá GOSU┬ i≤ precedeΣ b∙ assignment≤ t∩ thσ outpu⌠ lis⌠á variable≤ ì
nameΣ iε thσ call« I⌠ i≤ wortΦ mentioninτ tha⌠ sincσ inpu⌠ anΣ outpu⌠ list≤ arσ ì
similar¼á NBASI├á surround≤ theφ witΦ brace≤ anΣ brackets¼á respectively«á Thi≤ ì
avoid≤ codσ repetitioε anΣ make≤ scanninτ thσ list≤ morσ systematic.

Thσá res⌠á oµ thσ prograφ provide≤ fo≥ displayinτ anΣá printinτá thσá converteΣ ì
prograφá o≥á errors¼á fo≥á storinτ thσ succesfull∙ processeΣá prograφá anΣá fo≥ ì
subroutines.





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