Chapter 12

Answers to Exam Preparation Exercises

1. (a) Read (c) EOF (d) Write

3. One component type may be collected in one file.

4. Read(N), where N is a Real or Integer variable.

8. False; the indices must be ordinal, but the components can be of any type.

9. Code fragment:

TYPE

Score_Range = 0..100; (* a *)

Index_Range = 1..Max_Length;

Student_Scores = ARRAY[Index_Range] OF

Score_Range; (* b *)

VAR

Quiz_One: Student_Scores; (* c *)

10. (a)

TYPE

Bird_Type = (Cardinal, Blue_Jay, Humming_Bird, Robin);

(b)

Siting_Type = ARRAY[Bird_Type] OF Integer;

(c)

VAR Sitings: Siting_Type;

13. Output from the program:

11 15 -4

19 14 5

4 2 2

17 6 11

1 3 -2

52 40 12

14. Array variable declarations.

(a) 24-component Real array.

TYPE

IndexRange = 1..24;

RealType = ARRAY[IndexRange] OF Real;

VAR

RealArray:

RealType;

(b) 24-component Integer array.

TYPE

IndexRange = 24..47;

IntegerType = ARRAY[IndexRange] OF Integer;

VAR

IntegerArray:

IntegerType;

TYPE

IndexRange = 'A'..'Z';

BooleanType = ARRAY[IndexRange] OF Boolean;

VAR

BooleanArray:

BooleanType;

(d) 10-component Char array.

TYPE

IndexRange = -10..-1;

CharType = ARRAY[IndexRange] OF Char;

VAR

CharArray:

CharType;

17. Array elements are accessed directly by an index which gives the element's position within the array. File elements are accessed sequentially by a procedure or directly by a procedure which gives the file element's position in the file. All of the array elements are resident in memory; only one file element is in memory at a time.

18. (a) invalid (b) invalid (c) valid (d) invalid (e) valid (f) valid (g) valid

19. (a) A_Ref := Guide[71].Chart

(b) A_Code := Guide[88].Chart.Token[1]

(d) A_Ref.Symbol[20,9] := A_Map.Map_Code[4]

Answers to Programming Warm-Up Exercises

3. Declaration of a binary file.

TYPE

Real_File = FILE OF Real;

4. SeekEOF(Skipped)

5. Function that checks whether the next two records are identical.

FUNCTION Ident(VAR File1, File2: Data_Type): Boolean;

(* Pre: Files are open for reading *)

VAR

File1_Rec, File2_Rec : Rec_Type;

BEGIN

Read(File1, File1_Rec);

Read(File2, File2_Rec);

Ident := File1_Rec = File2_Rec

END;

8. Procedure to check for Score less than 60.

PROCEDURE CheckScore (VAR Failing:

FailType;

Score:

ScoreType;

ListLength:

IndexType);

VAR

Counter: (* Loop control variable *)

IndexType;

BEGIN (* CheckScore *)

FOR Counter := 1 TO ListLength DO

IF Score[Counter] < 60

THEN

Failing[Counter] := True

END; (* CheckScore *)

9. Procedure to check for a passing score.

PROCEDURE Check_Score (VAR Passing: Fail_Type;

Score: Score_Type;

List_Length: Index_Type);

VAR

Counter: Index_Type;

BEGIN (* Check_Score *)

FOR Counter := 1 TO List_Length DO

IF Score[Counter] >= 60

THEN Passing[Counter] := True

END; (* Check_Score *)

10. Function that returns number of passes.

FUNCTION TallyPass (Passing:

PassType;

ListLength:

IndexType):

Integer;

VAR

Counter: (* Loop control variable *)

IndexType;

Tally:

O..MaxLength;

BEGIN (* TallyPass *)

Tally := 0;

FOR Counter := 1 TO ListLength DO

IF Passing[Counter]

THEN

Tally := Tally + 1;

TallyPass := Tally

END; (* TallyPass *)

11. Function that checks for both passing and failing.

FUNCTION Error (Passing: Pass_Type;

Failing: Fail_Type;

List_Length: Index_Type): Boolean;

VAR

Counter: 1..MaxLength + 1;

Error_Found: Boolean;

BEGIN (* Error *)

Counter := 1;

Error_Found := False;

WHILE (Counter <= List_Length) AND NOT Error_Found DO

IF Passing[Counter] <> Failing[Counter]

THEN Counter := Counter + 1

ELSE Error_Found := True;

Error := Error_Found;

END; (* Error *)

14. Output as the code is written:

BCDE<eoln> The first and last characters are missing.

GHIJ<eoln> The last character is missing.

LMNO<eoln> The last character is missing.

<eof>

Corrected code:

Reset(In1);

Rewrite(Out1);

WHILE NOT EOF(In1) DO

BEGIN (* priming read has been removed *)

WHILE NOT EOLN(In1) DO

BEGIN

Read(In1, Character); (* read before writing *)

Write(Out1, Character);

END;

Readln(In1);

Writeln(Out1);

END;

15. Procedure to copy Input to a binary file:

TYPE

Bin_File = FILE OF Integer;

VAR

Data : Bin_File;

PROCEDURE Make_Bin_File (VAR Data: Bin_File);

VAR

Number: Integer;

BEGIN (* Make_Bin_File *)

Rewrite(Data);

Writeln('Enter one integer per line.');

Writeln('Signal end of file when done.');

WHILE NOT EOF DO

BEGIN

Readln(Number);

Write(Data, Number)

END;

END; (* Make_Bin_File *)

16. Program segment to read a set of part numbers:

CONST

Number_Of_Parts = 100;

TYPE

Part_Type = RECORD

Number : Integer;

Price : Real

END; (* Record *)

Part_Index = 1..Number_Of_Parts;

Part_Range = 0..Number_Of_Parts;

Parts_Type = ARRAY[Part_Index] OF Part_Type;

VAR

Parts: Parts_Type;

Temp_Part: Part_Type;

List_Length, Index: Part_Range;

BEGIN

List_Length := 0;

WHILE NOT EOF DO

BEGIN

Readln(Temp_Part.Number, Temp_Part.Price);

List_Length := List_Length + 1;

Parts[List_Length] := TempPart

END;