CP/M/CPM_CDROM.iso/mbug/mbug003.arc/PASCAL.010

Text File | 1979-12-31 | 10KB | 233 lines

PASCAL   FOR   BASIC   PROGRAMMERS

                               Dixon Kenney

                                  PART X.

     Thi≤á montΦá wσ arσ goinτ t∩ writσ thσ procedurσ whicΦ wil∞á edi⌠á an∙ ì
item«á  A≤á wel∞ a≤ editinτ aε item¼á s∩ tha⌠ an∙ fielΣ caε bσ changed¼á wσ ì
wil∞ havσ aε optioε whereb∙ thσ iteφ caε bσ markeΣ fo≥ deletion«á  Wσá onl∙ ì
marδ thσ item¼á s∩ that¼á durinτ aε editinτ session¼á wσ caε unmarδ it¼á iµ ì
necessary«á  Thσ actua∞ deletioε wil∞ bσ donσ b∙ ß separatσ function¼ whicΦ ì
wσ wil∞ looδ a⌠ nex⌠ time.

áááááááááProgrammer≤á iεá dBAS┼á I╔ wil∞ recognisσá thi≤á wa∙á oµ ì
ááááááááádeletinτá aε iteφ froφ ß database«á  Thi≤ wa∙ mean≤ tha⌠ ì
áááááááááthσá iteφá i≤ no⌠ deleteΣ unti∞ wσ arσ finall∙á surσá oµ ì
áááááááááwha⌠ wσ arσ doinτ - i⌠ give≤ u≤ thσ chancσ t∩ changσ ou≥ ì
ááááááááámind.

Procedure  Edit;

Const
  Header  =  '* EDIT AN EXISTING ITEM OF STOCK *';

Var
  PN, Pointer, Option  : Integer;
  Again, Found, More   : Boolean;
  YesNo, Yeah          : Char;

Begin

  Assign(PartFile, FileName);
  Reset(PartFile);

  Again := True;

  Repeat
    ClrScr;
    Writeln(' ':20, Header );
    Writeln;  Writeln;
    Write('Enter the Part Number of the item required : ');
    Readln(PN);

    With Part Do
      Begin
        Found := False;
        While not EOF(PartFile) and not Found do
          Begin
            Read(PartFile, Part);
            If PartNum = PN then
              Found := True;
            End;

        If not Found then
          Begin
            Writeln;  Writeln;
            Writeln('This item does not exist');
          End
        Elseè          Begin
            More := True;
            Pointer := FilePos(PartFile);
            Repeat
              Formwrite(Header);
              GoToXY(32, 4); Write(PartNum);
              GoToXY(32, 5); Write(Description);
              GoToXY(32, 7); Write(Cost:8:2);
              GoToXY(32, 8); Write(Retail:8:2);
              GoToXY(32,10); Write(MinOH);
              GoToXY(32,11); Write(MaxReorder);
              GoToXY(32,13); Write(CurrentOH);
              GoToXY( 1,18);
              Writeln('Type in the number of the field you wish to alter');
              Write('  or  99  to delete this item  ');
              Read(Option);

              Case Option of
                1 : Begin GoToXY(32, 4); ClrEOL; Read(PartNum)   End;
                2 : Begin GoToXY(32, 5); ClrEOL; Read(Description)   End;
                3 : Begin GoToXY(32, 7); ClrEOL; Read(Cost)   End;
                4 : Begin GoToXY(32, 8); ClrEOL; Read(Retail)   End;
                5 : Begin GoToXY(32,10); ClrEOL; Read(MinOH)   End;
                6 : Begin GoToXY(32,11); ClrEOL; Read(MaxReorder)   End;
                7 : Begin GoToXY(32,13); ClrEOL; Read(CurrentOH)   End;
               99 : Begin Deleted := Not Deleted;
                    If Deleted then
                      Begin  GoToXY(10,2); Write ('* DELETED *')  End
                    Else  Begin  GoToXY(10,2); ClrEOL  End;
                    End   { of Case = 99 }
              Else Begin
                GoToXY(1,22); Writeln('Not a valid option - try again');
                Delay(2000); GoToXY(1,22); ClrEOL
              End    { Else }
              End;   { Case Option }

              GoToXY(1,22);
              Write('Do you have another entry for this item [Y/N] ?');
              Read(Yeah);
              If UpCase(Yeah) = 'Y'
                Then More := True
                Else More := False
           Until More = False;

           Seek(PartFile,Pointer-1);
           Write(PartFile, Part);

         End     { of If Found }
       End;      { of With Part do }
       Writeln;   Writeln;

       Write('Do you want to look for another part [Y/N] ? ');
       Read(YesNo);
       If UpCase(YesNo) = 'Y' then
         Begin
         Again := True;
         Reset(PartFile)
         End
       Elseè         Again := False
     Until Again = False;
     Close(PartFile)

End;      { of Procedure Edit }

Comments on the code -

    MucΦá oµá wha⌠á i≤á donσ herσ i≤ repeateΣá froφá othe≥á procedures¼ ì
especiall∙ Procedurσ FindItem«á Wσ havσ t∩ finΣ thσ item¼á anΣ prin⌠ i⌠á t∩ ì
thσá screen«á  Oncσ tha⌠ i≤ done¼á wσ caε choosσ item≤ t∩ edit«á  Thσá casσ ì
Optioε statemen⌠ shoulΣ bσ familiar¼á excep⌠ fo≥ thσ ClrEO╠ function«  Thi≤ ì
functioεá clear≤ thσ curren⌠ screeε linσ froφ thσ positioε oµ thσ curso≥ t∩ ì
thσ enΣ oµ thσ line¼á bu⌠ i≤ doe≤ NO╘ movσ thσ cursor«á  Here¼ i⌠ blot≤ ou⌠ ì
thσ curren⌠ valuσ oµ thσ fielΣ whicΦ ha≤ beeε chosen¼á allowinτ thσ use≥ t∩ ì
typσ iε anothe≥ value¼á whicΦ i≤ theε read«á  Thσ FormWritσ listinτ ha≤á t∩ ì
modifieΣá s∩á tha⌠ choicσ number≤ arσ addeΣ beforσ eacΦ fielΣ labe∞á - thi≤ ì
give≤á u≤ thσ variou≤ number≤ t∩ choose«á  Choicσ 9╣ wil∞ alte≥á thσá fielΣ ì
Deleted¼á whicΦá wa≤á se⌠ t∩ Falsσ a⌠ datß entry¼á t∩ True«á  Wheneve≥á thσ ì
inidividua∞á iteφ i≤ listeΣ oε thσ screen¼á thσ strinτ "¬ DELETE─á *óá wil∞ ì
appea≥á a⌠á thσ heaΣ oµ thσ listing¼á t∩ sho≈ tha⌠ thσ iteφ i≤á markeΣá fo≥ ì
deletion«  B∙ typinτ 9╣ ß seconΣ time¼ thσ iteφ caε bσ undeleted.

     Oncσá thσ editinτ oµ thσ iteφ ha≤ beeε finished¼á wσ mus⌠ rewritσá thσ ì
recorΣ t∩ disk«á  Wheε wσ accesseΣ thσ recorΣ witΦ thσ ReaΣ state-ment¼ thσ ì
Filσá Pointe≥ wa≤ moveΣ t∩ poin⌠ t∩ thσ followinτ record«á  S∩ tha⌠ wσá caε ì
writσ thσ RecorΣ bacδ t∩ thσ correc⌠ placσ iε thσ file¼ wσ havσ t∩ movσ thσ ì
recorΣ pointe≥ bacδ onσ placσ t∩ poin⌠ t∩ thσ correc⌠ record«  Thi≤ i≤ donσ ì
iεá thσ "Seek(PartFile¼á Pointer-1)ó statement«á  Thσ valuσ oµ thσá curren⌠ ì
record'≤ pointe≥ wa≤ storeΣ wheε i⌠ wa≤ found¼á beforσ wσ wrotσ i⌠ t∩ disk¼ ì
iε thσ variablσ Pointer«á  Wheε thi≤ statemen⌠ i≤ executed¼á thσ pointe≥ i≤ ì
moveΣá agaiε froφ thσ beginninτ oµ thσ filσ t∩ thσ correc⌠ record«á  Wσ caε ì
theε writσ thσ recorΣ t∩ thσ filσ witΦ thσ usua∞ Writσ statement.

     Iµá wσá wan⌠á t∩ acces≤ anothe≥ record¼á wσ havσá t∩á star⌠á froφá thσ ì
beginninτ oµ thσ filσ again¼á sincσ thσ ne≈ recorΣ ma∙ bσ positioneΣ beforσ ì
thσ currentl∙ accesseΣ record«  S∩ wσ havσ t∩ Rese⌠ thσ filσ iε thσ "D∩ yo⌡ ì
wan⌠ another?ó section¼ iµ tha⌠ choicσ i≤ made.

     Iεá thσá previou≤á par⌠á oµá thi≤á series¼á wσá talkeΣá abou⌠á passinτ ì
parameter≤á t∩ ß Function«á  Thσ actua∞ situatioε oµ paramete≥ passinτ i≤ ß ì
littlσ morσ complicateΣ thaε wha⌠ wσ saiΣ there¼ however.

     Wheεá wσ passeΣ thσ paramete≥ oµ thσ FileNamσ iε thσ Functioεá Exists¼ ì
wσá actuall∙ onl∙ madσ ß cop∙ oµ thσ valuσ oµ thσ FileName¼á anΣ workeΣá oε ì
it«  Thi≤ i≤ calleΣ ß "valueó paramete≥ - wheε thσ procedurσ i≤ called¼ thσ ì
paramete≥ iε thσ calleΣ procedurσ i≤ initializeΣ t∩ thσ valuσ oµ thσ actua∞ ì
paramete≥ whicΦ correspond≤ t∩ i⌠ iε thσ call«á  Thσ actua∞ variablσ iε thσ ì
callinτ statemen⌠ i≤ protecteΣ froφ change.

     However¼á wσ ma∙ wan⌠ t∩ manipulatσ thσ actua∞ valuσ itself¼á anΣá no⌠ ì
jus⌠á ß cop∙ oµ it«á  Wσ d∩ thi≤ b∙ passinτ t∩ thσ procedurσ thσ Addres≤ oµ ì
thσ valuσ iε memory¼á s∩ tha⌠ thσ procedurσ manipulate≤ i⌠á directly«á  Thσ ì
paramete≥á iεá thσ procedurσ heade≥ i≤ theε calleΣ ß "variableóá parameter«  ì
I⌠á i≤ formeΣ b∙ writinτ thσ reserveΣ worΣ VA╥ iε fron⌠ oµ thσ variablσá o≥ ì
variable≤ b∙ whicΦ wσ arσ goinτ t∩ manip-ulatσ thσ value.


è     Herσ i≤ aε examplσ oµ Variablσ paramete≥ passinτ  ¿ takeε froφ thσá T╨ ì
Manual¼á p«á 132«á  Thσá Manua∞á ╔á aφá usinτá i≤ tha⌠á fo≥á Versioεá │á oµ ì
TurboPascal.)

     Procedure Switch ( Var a, b : Integer );
     Var    Tmp : Integer;
     begin
          Tmp := a; a := b; b := Tmp;
     end;

áááááááááThσá callinτ statemen⌠ -  Switch¿ i,Ω )╗á  wil∞ actuall∙ ì
áááááááááswitcΦ thσ value≤ oµ "ió anΣ "j"¼ whicΦ arσ addresseΣ iε ì
áááááááááthσ procedurσ b∙ thσ variablσ label≤ "aó anΣ "b".

ááááááááá     BotΦá Function≤ anΣ Procedure≤ caε usσ eithe≥á typσ ì
áááááááááoµ paramete≥ passing¼á anΣ thσ tw∩ type≤ caε bσ mixeΣ iε ì
áááááááááonσ procedurσ o≥ function«á  Herσ i≤ aε example¼ usinτ ß ì
áááááááááprocedurσ whicΦ compute≤ thσ intege≥ anΣ factiona∞ part≤ ì
áááááááááoµá ßá number«á  (Examplσ froφ "Probleφá Solvinτá .«á iε ì
áááááááááPascal¼áá b∙á Koffman¼á p.170¼á ßá booδá I'vσá mentioneΣ ì
ááááááááábefore.)

áááááProcedure Breakdown ( x    : Real;
ááááá                 Var Frac  : Real;
ááááá                 Var Whole : Integer);

áááááBegin
ááááá  Whole := Trunc(x);
ááááá  Frac  := x - whole
áááááEnd;

This procedure is called by the statement

     Breakdown ( a, r, i);
     Writeln(a:7:2, r:7:2, i:7);

áááááááááwherσ "aó i≤ ß rea∞ number¼á whosσ valuσ i≤ passeΣá int∩ ì
ááááááááá"xóá ("aóá itselµá i≤ no⌠ changeΣ b∙á thσá procedurσá )╗ ì
ááááááááá"Fracó anΣ "Wholeó actuall∙ manipulatσ thσ variable≤ "ró ì
ááááááááá(ßá real⌐ anΣ "ió (aε integer)¼á anΣ s∩ havσ thσ VA╥á iε ì
áááááááááfron⌠ oµ theφ iε thσ paramete≥ string.

ááááááááá     Iµá "aóá haΣá thσá valuσ 1.2│á wheεá Breakdowεá wa≤ ì
ááááááááácalled¼ thσ Writelε statemen⌠ woulΣ producσ thσ resul⌠ -    ì
ááááááááá1.2│     0.2│    1
ááááááááá
ááááááááá"róá anΣá "ió receivσ thei≥ value≤ froφá thσá procedure¼ ì
ááááááááárathe≥ thaε iε thσ callinτ program«  Thσ value≤ computeΣ ì
áááááááááiεá thσ procedurσ arσ addres-seΣ b∙ theφ - the∙ arσá no⌠ ì
ááááááááácopie≤ oµ thσ procedurσ values.

ááááááááá     Valuσá parameter≤ ¿ n∩ Va≥ ⌐ arσ one-wa∙á channels¼ ì
áááááááááfroφ cal∞ t∩ procedurσ o≥ function«  Variablσ parameter≤ ì
ááááááááá¿ witΦ VA╥ ⌐ arσ two-wa∙ communicatioε channels.

     Therσá i≤ mucΦ morσ t∩ learε iε Pascal¼á bu⌠ yo⌡ caε g∩ oε froφá here¼ ì
I'φ sure«  Koffman'≤ book≤ wil∞ bσ ß grea⌠ hel≡ t∩ you«  Oncσ you'vσ learn⌠ ì
Pascal¼á you'l∞ finΣ i⌠ ß better¼á albei⌠ ß longer¼ wa∙ oµ programminτ thaε ì
programminτ iε Basic.è