1. History of Computing – Pascal
Prof. Steven A. Demurjian
Computer Science & Engineering Department
The University of Connecticut
371 Fairfield Way, Box U-255
Storrs, CT
(860) 486–4818 (Office)
(860) (CSE Office)

2. GNU Pascal http://www.gnu-pascal.de/gpc/h-install.html
Suggest Dev-Pascal

3. Dev Pascal

4. New Source File

5. Cut and Paste in Code/Execute Compile

6. Hit Execute

7. Another Sample

8. Another Example

9. Read/Write from files letterGrades.txt A B D pointGrades.txt 4 3 1
program readwritetofiles;
var
readfilename : string;
writefilename : string;
myreadfile : text;
mywritefile : text;
c : char;
gpa : integer;
Begin (* put files in c:\Dev-Pas directory *)
readfilename:='letterGrades.txt';
writefilename:='pointGrades.txt';
assign(myreadfile, readfilename);
reset(myreadfile);
assign(mywritefile, writefilename);
rewrite(mywritefile);
while NOT EOF (myreadfile) do
begin
readln(myreadfile, c);
case (c) of
'A' : gpa := 4;
'B' : gpa := 3;
'C' : gpa := 2;
'D' : gpa := 1;
'F' : gpa := 0;
otherwise gpa := -1;
end; (* case *)
writeln(mywritefile, gpa);
end;
writeln(mywritefile,'Completed writing');
close(myreadfile);
close(mywritefile);
end.
letterGrades.txt A B D
pointGrades.txt 4 3 1
Completed writing

10. Reading and writing lines
program readwritetofiles;
var
readfilename : string;
writefilename : string;
myreadfile : text;
mywritefile : text;
line : packed array [1..100] of char;
begin
(* put files in c:\Dev-Pas directory *)
readfilename:='inputfile.txt';
writefilename:='outputfile.txt';
assign(myreadfile, readfilename);
reset(myreadfile);
assign(mywritefile, writefilename);
rewrite(mywritefile);
while NOT EOF (myreadfile) do
readln(myreadfile, line);
writeln(mywritefile, line);
end;
writeln(mywritefile,'Completed writing');
close(myreadfile);
close(mywritefile);
end.
inputfile.txt
Here is a file
with multiple
words that you also
have to process
outputfile.txt
Here is a file
with multiple
words that you also
have to process
Completed writing
For Pascal Project – read a line at a time and Process the array of char

11. Even worked on HoCMoviesAssignment.txt
terms assessing the ?realistic? nature of the computing in the movie as compared to the release time
In this assignment related to HoC, you are to select one of the movies listed below to watch and rev
movie. You are to assess the movies in terms of HoC in regards to the following questions:
1. Identify and discuss technologies/software in the movie.
3. Are the technologies/software Futuristic at time Movie Released?
2. Are the technologies/software Realistic at time Movie Released?
4. Are any of the Futuristic technologies/software available today?
5. When did the Futuristic technologies/software become available?
6. Are any of Futuristic technologies/software still not available? On the horizon?
7. Does the movie contain technologies/software now Available?
8. Identify and discuss any ethical, social, or professional issues in the movie.
9. Any other pertinent information related to HoC?
These movies were selected from:
* Billion Dollar Brain (1967)
* Desk Set (1957)
* 2001: A Space Odyssey (1968)
* The Computer Wore Tennis Shoes (1969)
* Colossus: The Forbin Project (1970)
* The Aries Computer (1972)
* The Andromeda Strain (1971)
* Demon Seed (1977)
* Blade Runner (1982)
* Tron (1982)
* Electric Dreams (1984)
* WarGames (1983)
* D.A.R.Y.L. (1985)
* Prime Risk (1985)
* Flight of the Navigator (1986)
* Defense Play (1989)
* Short Circuit (1986)
* Sneakers (1992)
* Disclosure (1994)
* Hackers (1995)
* The Net (1995)
If you have another movie, before 1995, that you want to review, please me for approval.
Deliverable: 2 page MS word document that explores answers each of the questions given above. 1 pag
is 12pt, 1in margins, single spaced, Times New Roman fonts. You must submit an MS Word Document. ?
You can use the next page as a template for your submission.
Name:
Movie:
HoC Movies Assessment/Analysis Assignment
Completed writing

12. Getting Started With Pascal Programming
Getting Started With Pascal Programming

13. Basic Structure Of Pascal Programs
Program name.p (Pascal source code)
Part I: Header
Program documentation
program name (input, output);
Part II: Declarations
const :
Part III: Statements
begin :
end.

14. Details Of The Parts Of A Pascal Program
Headers
Program documentation
Version number, date of last modification, what does the program do etc.
Comments for the reader of the program (and not the computer)
(* Marks the beginning of the documentation
*) Marks the end of the documentation
Program heading
Name of program, input and/or output operations performed by the program
Example (*
* Tax-It v1.0: This program will electronically calculate your tax return. *)
program taxIt (input, output);

15. The Smallest Pascal Program(*
* Smallest.p:
* The smallest Pascal program that will still compile written by James Tam
* v1.0. *)
program smallest;
begin
end.
Note: The name "smallest" should match the filename "smallest.p". You can find an online version of this program in the Unix file system under /home/231/examples/intro/smallest.p (the compiled version is called "smallest").

16. Variables Set aside a location in memory
Used to store information (temporary)
Types:
integer – whole numbers
real – whole numbers and fractions
Can't start or end with a decimal
char – alphabetic, numeric and miscellaneous symbols
boolean – true or false values
Usage:
Declaration
Accessing or assigning values to the variables
Real – complete – must include a fractional and a whole number portion e.g., 82.1 not 82.
Getting Started With Pascal Programming

17. Declaring Variables (2)
Occurs in the variable declaration ("var") section
i.e.,
var
name of first variable, name of second variable…: type of variables;
e.g.,
height, weight: real;
age: integer;

18. Accessing And Assigning Values To Variables (2)
Assignment
Performed via the assignment operator :=
Usage:
Destination := Source;1
Example:
x := 5;
x:= y;
interest := principle * rate;
character := 'a';
Avoid assigning mixed types
e.g.,
var
num1: integer;
num2: real;
begin
num1 = 12;
num2 = 12.5;
num2 := num1;
1 The source can be any expression (constant, variable or formula)
Not allowed!
num1 := num2;

19. Named Constants (2) Examples: const TAXRATE = 0.25; SAMPLESIZE = 1000;
YES = True;
NO = False;

20. Output Displaying information onscreen
Done via the write and writeln statements
Syntax (either write or writeln):
write ('text message'); or
writeln('text message');
write(name of variable or constant);
writeln (name of variable or constant);
write('message', name of variable, 'message'…);
writeln('message', name of variable, 'message'…);

21. Output (2) Examples: var num : integer; begin num := 10;
writeln('line1');
write('line2A');
writeln('line2B');
writeln(num);
writeln('num=',num);
line1
line2Aline2B 10
num=10
Getting Started With Pascal Programming

22. Automatic formatting of output
Formatting Output
Automatic formatting of output
Field width: The computer will insert enough spaces to ensure that the information can be displayed.
Decimal places: For real numbers the data will be displayed in exponential form.
Manually formatting of output:
Syntax:
write or writeln (data: Field width for data: Number decimal places for data);
Getting Started With Pascal Programming

23. Formatting Output (2) Examples var num : real; begin num := 12.34;
writeln(num);
writeln(num:5:2);
e+01
12.34
Getting Started With Pascal Programming

24. Formatting Output (3)
If the field width doesn’t match the actual size of the field
Field width too small – extra spaces will be added for numerical variables but not for other types of data.
Examples:
num := ;
writeln(num:3);
writeln('123456':3);
Field width too large – the data will be right justified (extra spaces will be put in front of the data).
num := 123;
writeln(num:6);
Writeln('123':6);
Eg1.,
Eg2., 123
Eg3.,---123
Eg4.,---123
Getting Started With Pascal Programming

25. Formatting Output (4)
If the number of decimal places doesn’t match the actual number of decimal places.
Set number of decimal places less than the actual number of decimal places – number will be rounded up.
Example:
num1 :=
writeln (num1:6:2);
Set number of decimal places greater than the actual number of decimal places – number will be padded with zeros.
num1 := ;
writeln(num1:6:6);
e.g1.,
e.g2.,
Getting Started With Pascal Programming

26. Formatting Output: A Larger Example
For the complete program and executable look under /home/231/examples/intro/out1.p (out1 for the compiled version)
program out1;
var
num1 : integer;
num2 : real;
begin
num1 := 123;
num2 := ;
writeln('Auto formatted by Pascal', num1, num2);
writeln('Manual format':13, num1:3, num2:7:3);
writeln('Manual not enough':13, num1:2, num2:6:3);
writeln('Manual too much':16, num1:4, num2:8:4);
end.
Auto formatted by Pascal e+02
Manual format
Manual not en
Manual too much
Getting Started With Pascal Programming

27. Input The computer program getting information from the user
Done via the read and readln statements
Syntax:
(single input)
read (name of variable); or
readln (name of variable);
(multiple inputs)
read (nv1, nv2…);
readln (nv2, nv3…);

28. Input (2) Examples: var num1, num2 : integer begin read (num1);
read (num1, num2);

29. Input: Read Vs. Readln Both: Read Readln
Reads each value inputted and matches it to the corresponding variable.
Read
If the user inputs additional values they will remain
Readln
Any additional values inputted will be discarded

30. Input: Read Vs. Readln (An example)
For the complete version of this program look in Unix under: /home/231/examples/intro/read1.p (or read1 and read2 for the compiled version)
e.g., read1.p
write('Input some integers making sure to separate each one with a space ');
write('or a new line: ');
read (num1, num2);
write('or a newline: ');
read(num3, num4);
Getting Started With Pascal Programming

31. Input: Read Vs. Readln (An example (2))
For the complete version of this program look in Unix under: /home/231/examples/intro/read2.p (or read2 for the compiled version)
e.g., read2.p
write('Input some integers making sure to separate each one with a space ');
write('or a newline: ');
readln (num1, num2);
readln(num3, num4);
5 6
Getting Started With Pascal Programming

32. Extra Uses Of Readln To filter out extraneous input As an input prompt
e.g.,
writeln('To continue press return');
readln;

33. Remaining Topics Arrays Conditionals Looping Files
Multi-Dimensional Arrays
Functions/Procedures
Pointers and Lists \

34. Arrays const CLASSSIZE = 5; var
classGrades : array [1..CLASSSIZE] of real;
i : integer;
total, average : real;
begin
total := 0;

35. for i := 1 to CLASSSIZE do begin
write('Enter grade for student no. ', i, ': ');
readln (classGrades[i]);
total := total + classGrades[i];
end;
average := total / CLASSSIZE;
writeln;
writeln('The average grade is ', average:6:2, '%');
writeln('Grade for student no. ', i, ' is ', classGrades[i]:6:2, '%');

36. CONDITIONALS: If-Then-Else (Simple Body)
Body of if-then-else consists of a single statement
Format:
if (Boolean Expression) then s1
else
s2;
s3;
No semi-colon (indicates end of decision-making!)

37. If-Then-Else (Simple Body(2))
Example (for full example look under /home/231/examples/decisions/simpleIfThenElse.p):
if (x = 1) then
writeln('body of if')
else
writeln('body of else');
writeln('after if-then-else');

38. If-Then-Else (Compound Body)
Body of if-then-else consists of multiple statements
Format:
if (Boolean Expression) then
begin
s1; :
sn;
end
else
sn+1;
sn + m;
end;
Sn + m + 1;
No semi-colon (marks end of decision-making!)

39. If-Then (Compound Body(2))
Example (for full example look under /home/231/examples/decisions/compoundIfThenElse.p):
if (x = 1) then
begin
writeln('Body of if 1');
writeln('Body of if 2');
end
else
writeln('Body of else 1');
writeln('Body of else 2');
end;
writeln('after if-then-else');

40. Case Statements
An alternative to the if, else-if (only one condition is true)
Format (integer):
Case (expression) of
i1:
body;
i2: :
in:
otherwise:
Expression (variable, constant, arithmetic) must evaluate to an integer

41. Case Statements: Integer Example
Example (look for complete example in Unix under /home/231/examples/decisions/caseOf1.p):
case (gpa) of 4:
begin
writeln(‘You got an A’);
end; (* GPA of 4 *) 3:
writeln(‘You got a ‘B’);
end; (* GPA of 3 *) 2:
begin
writeln(‘You got a C’);
end; (* GPA of 2 *) 1:
writeln(‘You got a D’);
end; (* GPA of 1 *) 0:
writeln(‘You got an F’);
end; (* GPA of 0 *)
end; (* case *)

42. Case Statements: Characters
Format (char):
Case (expression) of
‘c1’:
body;
‘c2’: :
‘cn’:
otherwise
Expression (variable, constant, arithmetic) must evaluate to a character

43. Case Statements: Character Example
case (letter) of
‘A’:
begin
writeln(‘GPA = 4’);
end; (* GPA of 4 *)
‘B’:
writeln(‘GPA = 3’);
end; (* GPA of 3 *)
‘C’:
begin
writeln(‘GPA = 2’);
end; (* GPA of 2 *)
‘D’:
writeln(‘GPA = 1’);
end; (* GPA of 1 *)
‘F’:
writeln(‘GPA = 0’);
end; (* GPA of 0 *)
end; (* case *)

44. Pre-Test Loop: While-Do
Can be used if the number of times that the loop executes is not known in advance.
Syntax:
while (Boolean expression) do
body
Example (Full text-only version can be found in Unix under /home/231/examples/repetition/whileDo.p)
i: = 1;
while (i <= 10) do
begin
writeln('i = ', i);
i := i + 1;
end; (* while *)
Initialize control
Test condition
Execute body
Update control

45. First For Loop Example
Example one (A compilable text-only version can be found in Unix under /home/231/examples/repetition/forLoopUp.p)
var
i, total : integer;
begin
total := 0;
for i := 1 to 10 do
total := total + i;
writeln('i = ':4, i:2, 'total = ':13, total:2);
end; (* for *)
end.
Initialize control
Update control
Test condition
Execute body

46. Second For Loop Example
Example one (A compilable text-only version can be found in Unix under /home/231/examples/repetition/forLoopDown.p)
var
i, total : integer;
begin
total := 0;
for i := 5 downto 1 do
total := total + i;
writeln('i = ':4, i:2, 'total = ':13, total:2);
end; (* for *)
end.

47. Post Test Loops: Repeat-Until
Used instead of a while-do loop if you need the loop to execute at least once.
Syntax:
repeat
body
until (Boolean expression);

48. Repeat-Until: An Example (2)
begin
answer := trunc(Random * MAX);
write('Enter your guess: ');
readln(guess);
if (guess = answer) then
writeln('You guessed correctly!')
else
writeln('You guessed incorrectly');
writeln('Play again?');
writeln('Enter "Y" or "y" to play again');
writeln('Enter "N" or "n" otherwise');
write('Choice: ');
readln(choice);
end;
until (choice = 'N') OR (choice = 'n');
Execute body
Test condition
Initialize control
Update control

49. Infinite Loops
Loops that never end (the stopping condition is never met).
Infinite loops can be caused by logical errors:
The loop control is never updated (Example 1).
The updating of the loop control never brings it closer to the stopping condition (Example 2).
Example 1 (a compilable version can be found in Unix under /home/231/examples/repetition/infinite1.p)
i := 1;
while (i < 10) do
writeln ('i = ', i);
To stop a program with an infinite loop in Unix simultaneously press the <ctrl> and the <c> keys

50. Nested Loops One loop executes inside of another loop(s).
Example structure:
Outer loop (runs n times)
Inner loop (runs m times)
Body of inner loop (runs n x m times)
Example program (complete compilable program can be found in Unix under:
/home/231/examples/repetition/nested.p)
for i := 1 to 2 do
for j := 1 to 3 do
writeln('i = ':9, i, 'j = ':9, j);
writeln('All done!');

51. FILES: Indicating What File You Are Reading From
Syntax:
program name (name of input file1);
Example:
program grades (output, letterGrades);
A variable that is associated with a file on disk
Syntax:
name of file2 : text;
Example:
letterGrades : text;
1 The name of input file must correspond to an actual file in the same directory that the executable program resides
2 The name of file variable must correspond to an actual file in the same directory that the executable program resides

52. Opening Files Purpose: Syntax: Example:
Prepares the file for reading (positions the file pointer)
Syntax:
reset (name of input file3);
Example:
reset(letterGrades);
3 The name of file being opened must correspond to an actual file in the same directory that the executable program resides

53. Reading Information From Files
Performed with read or readln
Syntax:
read (name of input file4, variable(s));
readln (name of input file4, variable(s));
Example:
readln(letterGrades, letter);
4 The name of file being read from must correspond to an actual file in the same directory that the executable program resides

54. Reading Information From Files (2)
Typically reading is done within the body of a loop
Syntax:
while NOT EOF (name of input file5) do
begin
read (name of input file5, variable(s));
readln (name of input file5, variable(s));
end; (* Done reading from input file *)
Example:
while NOT EOF (letterGrades) do
readln(letterGrades, letter);
writeln(letter);
end; (* Loop to read letter grades file *)
5 The name of the input file must correspond to an actual file in the same directory that the executable program resides

55. Alternative Approach To Reading Files
Employ a sentinel in the file
Keep reading from the file until the sentinel value is encountered
Example:
var
inputFile : text;
num : integer;
: :
readln (inputFile, num);
while NOT (num = -1) do
begin
writeln(num);
readln(inputFile, num);
end; (* Done reading input file *)

56. Reading From Files: Putting It All Together
program grades (output, letterGrades);
var
letterGrades : text;
letter : char;
begin
reset(letterGrades);
writeln('Opening file "letterGrades" for reading.');
while NOT EOF (letterGrades) do
readln(letterGrades, letter);
writeln(letter);
end; (* Loop to read letter grades file *)
close(letterGrades);
writeln('Completed reading of file "letterGrades"');
end. (* End of program *)

57. Opening The File Two methods:
Rewriting – erases the old contents of the file (rewrites over what was already there).
Appending – retain the old contents of the file (appends the new information at the end).
Syntax (rewriting / appending):
rewrite (name of file); append (name of file);
Example (rewriting / appending):
rewrite(gradePoints); append(gradePoints);

58. Writing To A File: Putting It All Together
A complete version of this program can be found in Unix under: /home/231/examples/files/grades2.p
program grades (output, letterGrades, gradePoints);
var
letterGrades : text;
gradePoints : text;
letter : char;
gpa : integer;
begin
reset(letterGrades);
rewrite(gradePoints);
writeln('Opening file "letterGrades" for reading.');
writeln('Opening file "gradePoints" for writing.');
while NOT EOF (letterGrades) do

59. Writing To A File: Putting It All Together (2)
readln(letterGrades, letter);
case (letter) of
'A' : gpa := 4;
'B' : gpa := 3; 'C' : gpa := 2;
'D' : gpa := 1;
'F' : gpa := 0;
otherwise gpa := -1;
end; (* case *)
writeln(gradePoints, gpa);
end; (* Loop to read letter grades file *)
writeln('Finished reading and writing to files.');
close(letterGrades);
close(gradePoints);
end.

60. Details Of Write And Writeln For Files: Intuitive View
Program statement Effect on file
rewrite (data); (Open file "data" and position
^ file pointer at start)
write (data, 'x'); x ^
write(data, 'y'); xy
write(data, 'z'); xyz
writeln(data); xyz _
write(data,'a'); xyz a

61. Details Of Write And Writeln For Files: Actual View
Program statement Effect on file
rewrite (data); (Open file "data" and position
^ file pointer at start)
write (data, 'x'); x ^
write(data, 'y'); xy
write(data, 'z'); xyz
writeln(data); xyz<EOL>
write(data,'a'); xyz<EOL>a
A file does not consist of physical lines but instead it's a continuous stream of characters

62. Details Of Read And Readln For Files: Intuitive View1
Program statement Effect on file Effect in program
reset (data); xyz (Open file "data" and position
^ file pointer at start) a
read(data, ch); xyz Value of ch: 'x' ^
readln(data, ch); xyz Value of ch: 'y' ^
read(data, ch); xyz Value of ch: 'a'
1 Assume that the code on the previous slide has created the file called "data"

63. Details Of Read And Readln For Files: Actual View1
Program statement Effect on file Effect in program
reset (data); xyz<EOL>a (Open file "data" and position
^ file pointer at start)
read(data, ch); xyz<EOL>a Value of ch: 'x' ^
readln(data, ch); xyz<EOL>a Value of ch: 'y' ^
read(data, ch); xyz<EOL>a Value of ch: 'a' ^
read(data,ch); xyz<EOL>a
1 Assume that the code on the previous slide has created the file called "data"

64. Details Of Read And Readln For Files: Actual View1
Program statement Effect on file Effect in program
reset (data); xyz<EOL>a (Open file "data" and position
^ file pointer at start)
read(data, ch); xyz<EOL>a Value of ch: 'x' ^
readln(data, ch); xyz<EOL>a Value of ch: 'y' ^
read(data, ch); xyz<EOL>a Value of ch: 'a' ^
read(data,ch); xyz<EOL>a Error – reading past end of file
1 Assume that the code on the previous slide has created the file called "data"

65. Passing File Variables As Parameters
Must be passed as variable parameters only.
Syntax:
procedure nameProcedure (var nameFile :text);
Example:
procedure fileInputOuput (var letterGrades : text;
var gradePoints : text);

66. MULTI-DIMENSIONAL ARRAYS: When To Use Arrays Of Different Dimensions
Determined by the data – the number of categories of information determines the no. of dimensions to use.
Examples:
(1D array)
Tracking grades for a class
Each cell contains the grade for a student i.e., grades[i]
There is one dimension that specifies the student
(2D array)
Personal finances program
One dimension of information specifies the financial category (cash in or cash out).
The other dimension is used to specify the time
One dimension (which student)

67. When To Use Arrays Of Different Dimensions (2)
(2D array continued)
Time
Financial category
January
February
March …
Income
-Rent
-Food
-Fun
-Transport
-Misc
Net income

68. When To Use Arrays Of Different Dimensions (3)
(2D array continued)
Notice that each row is merely a 1D array
(A 2D array is an array containing rows of 1D arrays)
[1]
[2]
[3]
[4]
Income
[1]
[2]
[3]
[4]
[5]
[6]
[7]
-Rent
-Food
-Fun
-Transport
-Misc
Net income

69. When To Use Arrays Of Different Dimensions (5)
-Misc
Income
-Rent
-Food
Net income
-Transport
-Fun
March …
February
January
John’s finances
Mary’s finances
Bob’s finances

70. Declaring Multi-Dimensional Arrays
Syntax:
(Two dimensional arrays)
Name : array [min..max, min..max] of type;
(Three dimensional arrays)
Name : array [min..max, min..max, min..max] of type;
Example:
johnFinances : array [1..7, 1..7] of real;
cube : array[1..3, 1..4, 1..6] of char;
Rows
Columns
Syntax:
name [row][column] := name [row][column];
finances [1][1] := 4500;
writeln (finances[1][1]);

71. Example Program: Map Generator And Editor
program map (input, output);
const
MAXROWS = 10;
MAXCOLUMNS = 10;
var
world : array[1..MAXROWS, 1..MAXCOLUMNS] of char;
r, c : integer;
randomValue : real;
quitChoice : char;
editChoice : char;
rowToEdit : integer;
columnToEdit : integer;
charToChange : char;

72. Example Program: Map Generator And Editor (2)
begin
for c := 1 to MAXCOLUMNS do
world[1][c] := '-';
world[MAXROWS][c] := '-';
for r := 1 to MAXROWS do
world[r][1] := '|';
world[r][MAXCOLUMNS] := '|';

73. Example Program: Map Generator And Editor (3)
for r := 2 to (MAXROWS-1) do
begin
for c:= 2 to (MAXCOLUMNS-1) do
randomValue := Random;
if (randomValue <= 0.05) then
world [r][c] := '~'
else if (randomValue <= 0.25) then
world [r][c] := '^'
else if (randomValue <= 0.30) then
world [r][c] := 'C'
else if (randomValue <= 0.40) then
world [r][c] := 'T'
else
world [r][c] := ' ';
end; (* inner for *)
end; (* outer for *)

74. Example Program: Map Generator And Editor (4)
repeat
begin
for r := 1 to MAXROWS do
for c := 1 to MAXCOLUMNS do
write(world[r][c]);
end; (* inner for loop *)
writeln;
end; (* for loop - displays world *)
write('Enter "Y" or "y" if you wish to edit the world or the return ');
write('key otherwise: ');
readln(editChoice);

75. Example Program: Map Generator And Editor (5)
if (editChoice = 'Y') OR (editChoice = 'y') then
begin
writeln;
write('Enter row (2 - 9) to edit: ');
readln(rowToEdit);
write('Enter column (2 - 9) to edit: ');
readln(columnToEdit);
if (rowToEdit < 2) OR (rowToEdit > (MAXROWS-1))
OR (columnToEdit < 2) OR
(columnToEdit > (MAXCOLUMNS-1)) then
writeln('Value for row must be in the range of 2 - 9')

76. Example Program: Map Generator And Editor (6)
else
begin
writeln('What do wish to change this square to? Choices include:');
writeln('"~" for water');
writeln('"^" for trees');
writeln('"C" for a city');
writeln('"T" for a town');
writeln('" " (A space) for an open field');
write('Enter choice and hit return: ');
readln(charToChange);
world[rowToEdit][columnToEdit] := charToChange;
end; (* else *)
end; (* if edit mode chosen. *)
writeln('Type "Q" or "q" to quit, or return to continue: ');
readln(quitChoice);
end; (* repeat loop *)
until (quitChoice = 'Q') OR (quitChoice = 'q');
end.

77. RECORDS: Declaring Types
Syntax:
Type
Name(1) = Type for name (1);
Name(2) = Type for name (2);
: : : :
Name(n) = Type for name (n);
Example:
World = array [1..20,1..20] of char;
Var
map : World;
biosphere: World;

78. Declaring Types (3)
Can be used to provide alternative names for existing types
Example:
type
FloatingPoint = real;
var
gpa : FloatingPoint;
income: real;

79. Declaring Types (3)
Can be used to provide alternative names for existing types
Example:
type
FloatingPoint = real;
var
gpa : FloatingPoint;
income: real;
Original type still usable

80. Declaring Types (4) Example: Type world = array [1..20,1..20] of char;
Var
map : world;
biosphere: world;
Declaring the type - defining what the type consists of
Declaring variables of the new type

81. Where Type Declarations Fit Into Pascal Programs
program name;
(* Declarations *)
const (* Declaration of constants)
type (* Declaration of new types *)
var (* Declaration of variables *)
(* Declarations of functions & procedures – defining
what they do *)
begin
end.

82. Declaring Records Syntax: Name = record
name of field (1) : type of field (1);
name of field (2) : type of field (2);
name of field (3) : type of field (3);
: : : : : :
name of field (n) : type of field (n);
end; (* Record declaration *)

83. Declaring Records (2) Example: Syntax: Example: StudentRecord = record
studentIdentification : integer;
firstName : array [1..20] of char;
lastName : array [1..20] of char;
initial : char;
addressLineOne : array [1..20] of char;
addressLineTwo : array [1..20] of char;
phoneNumber : integer;
end;
Syntax:
name of variable : name of declared record;
Example:
jamesTam : studentRecord;
bartSimpson : studentRecord;

84. Declaring Arrays Of Records
Method:
1) Declare the record
2) Declare a type for the array of records
The second step is essential in Pascal for passing the array as a parameter into functions and procedures!

85. Declaring Arrays Of Records
type
StudentRecord = record
studentIdentification : integer;
firstName : array [1..20] of char;
lastName : array [1..20] of char;
initial : char;
addressLineOne : array [1..20] of char;
addressLineTwo : array [1..20] of char;
phoneNumber : integer;
end;
StudentRecordList = array [ ] of StudentRecord;
var
universityOfCalgaryStudentRecords : StudentRecordList;

86. Declaring Arrays Of Records
type
StudentRecord = record
studentIdentification : integer;
firstName : array [1..20] of char;
lastName : array [1..20] of char;
initial : char;
addressLineOne : array [1..20] of char;
addressLineTwo : array [1..20] of char;
phoneNumber : integer;
end;
StudentRecordList = array [ ] of StudentRecord;
var
universityOfCalgaryStudentRecords : StudentRecordList;
Declaring Record
Declaring a new type
Declaring a new instance of type "StudentRecordList"

87. Passing Records And Arrays Of Records As Parameters
Looks the same as passing in other types of variables
Can be passed in as value or variable parameters
Examples (function or procedure calls):
displayStudent (jamesTam);
initializeStudentRecords (universityOfCalgaryStudentRecords);
Examples (function or procedure definition)
procedure displayStudent (jamesTam :StudentRecord);
begin
end; (* Procedure displayStudent *)
procedure initializeStudentRecords (var
universityOfCalgaryStudentRecords : StudentRecordList);
end; (* Procedure initializeStudentRecords *)

88. Returning Composite Types From Functions
You cannot return composite types of variables (arrays and records) from functions.
To have changes to these types of variables be retained after the function or procedure has ended they must be passed as variable parameters (example shown on previous slide)

89. Using Record Variables
Indicate which variable you wish to use (by stating the name of the variable)
e.g.,
type
Person = Record
name : array [1..8] of char;
age : integer;
height : real;
weight : real;
end; (* Declaration of Person *)
begin
jo, jack : Person;

90. Using Record Variables (2)
(If applicable) indicate which field of the record that you wish to use.
e.g.,
jo.name := 'joanne';
jo.age := 20;
jo.height := 68.5;
jo.weight := 110;
Assignment
Can be done on a field by field basis:
jack.age = jo.age;
Can be done for the whole record (if the records are the same type)
jack := jo;

91. Using Record Variables (3)
Input and output via read/readln and write/writeln
Must be done on a field by field basis
e.g.,
write('Enter age for Jack : ');
readln(jack.age);
writeln('Jack is ', jack.age, ' years old);

92. A Shortcut For Referencing All The Fields Of A Record: With-do
Allows you to refer to the fields of a record without having to constantly refer to the name of the record variable.
Syntax:
with name do
body
Example:
with jack do
begin
writeln('Jack's stats');
writeln('Age: ', age);
writeln('Height :', height);
writeln('Weight :', weight);
end; (* With do for jack *)

93. Putting This All Together
You can find a version of this program in Unix under:
/home/231/examples/records/person.p
program person (input, output, peopleValues);
const
NAMELENGTH = 16;
NOPEOPLE = 4;
type
Person = Record
name : array [1..NAMELENGTH] of char;
age : integer;
height : real;
weight : real;
end; (* Declaration of Person *)
People = array [1..NOPEOPLE] of Person;
var
peopleValues : text;

94. Putting This All Together (2)
procedure manuallyInitializeCalgaryPeople (var calgaryPeople : People );
var
i : integer;
begin
for i := 1 to NOPEOPLE do
with calgaryPeople[i] do
write('Enter name of person: ');
readln(name);
write('Enter age of person in whole years: ');
readln(age);
write('Enter the height of the person in inches: ');
readln(height);
write('Enter the weight of the person in pounds: ');
readln(weight);
writeln;
end; (* With-do *)
end; (* Initialization for-loop *)
end; (* Procedure manuallyInitializeCalgaryPeople *)

95. Putting This All Together (3)
procedure defaultInitializeCalgaryPeople (var calgaryPeople : People);
var
i : integer;
begin
reset(peopleValues);
writeln('Reading initial values from file "peopleValues"');
for i := 1 to NOPEOPLE do
with calgaryPeople[i] do
readln(peopleValues,name);
readln(peopleValues,age);
readln(peopleValues,height);
readln(peopleValues,weight);
readln(peopleValues);
end; (* With-do *)
end; (* Initialization for-loop *)
close(peopleValues);
end; (* Procedure defaultInitializeCalgaryPeople *)

96. Putting It All Together (4)
procedure displayCalgaryPeople (calgaryPeople : People);
var
i : integer;
begin
writeln;
for i := 1 to NOPEOPLE do
with calgaryPeople[i] do
writeln('Name: ', name);
writeln('Age: ', age);
writeln('Height: ', height:0:2);
writeln('Weight: ', weight:0:2);
end; (* With-do *)
end; (* Display for-loop *)
end;

97. Putting It All Together (5)
begin
var calgaryPeople : People;
var initializationMethod : integer;
writeln;
writeln('Select method to set starting values for the people');
writeln('Enter "1" to read the values in from a file');
writeln('Enter "2" to manually enter in the values yourself');
write('Enter your choice: ');
readln(initializationMethod);
case (initializationMethod) of
1 :
defaultInitializeCalgaryPeople(calgaryPeople);
displayCalgaryPeople(calgaryPeople);
end;
2 :
manuallyInitializeCalgaryPeople(calgaryPeople);

98. Putting It All Together (6)
begin
var calgaryPeople : People;
var initializationMethod : integer;
writeln;
writeln('Select method to set starting values for the people');
writeln('Enter "1" to read the values in from a file');
writeln('Enter "2" to manually enter in the values yourself');
write('Enter your choice: ');
readln(initializationMethod);
case (initializationMethod) of
1 :
defaultInitializeCalgaryPeople(calgaryPeople);
displayCalgaryPeople(calgaryPeople);
end;
2 :
manuallyInitializeCalgaryPeople(calgaryPeople);

99. Putting It All Together (6)
otherwise
begin
writeln('Your choice was not one of the available options.');
writeln('Restart program and select again.');
end; (* otherwise *)
end; (* case *)
writeln;
end.

100. FYI – REST NOT LIKELY NEEDED FOR PASCAL PROGRAMMING ASSGINMENT FUNCTIONS AND PROCEDURES Defining Procedures
Syntax (Basic case – no parameters):
procedure name;
begin
(* Statements of the function go here *)
end; (* End of procedure name *)
Example (Basic case – no parameters):
procedure displayInstructions;
writeln ('These statements will typically give a high level');
writeln('overview of what the program as a whole does');
end; (* End of procedure displayInstructions *)

101. Procedures: Putting Together The Basic Case
procedure displayInstructions;
begin
writeln ('These statements will typically give a high level');
writeln('overview of what the program as a whole does');
end; (*Procedure displayInstructions *)
displayInstructions;
writeln('Thank you, come again!');
end. (* Program *)

102. Procedures: Putting Together The Basic Case
procedure displayInstructions;
begin
writeln ('These statements will typically give a high level');
writeln('overview of what the program as a whole does');
end; (*Procedure displayInstructions *)
displayInstructions;
writeln('Thank you, come again!');
end. (* Program *)
Procedure definition
Procedure call

103. Defining Procedures With Parameters
Syntax:
procedure name (Name of parameter 1 : type of parameter 1;
Name of parameter 2 : type of parameter 2;
: :
Name of parameter n : type of parameter n);
begin
(* Statements of the function go here *)
end;
Example:
procedure celciusToFahrenheit (celciusValue : real);
var
fahrenheitValue : real;
fahrenheitValue := 9 / 5 * celciusValue + 32;
writeln(temperature in Celsius: ', celciusValue:0:2);
writeln(temperature in Fahrenheit: ', fahrenheitValue:0:2);
end; (* Procedure celciusToFahrenheit *)

104. Procedures: Putting Together The Case With Parameters
A compilable version of this example can be found in Unix under /home/231/examples/functions/temperatureConverter..p
program temperatureConverter (input, output);
var
celciusValue : real;
procedure celciusToFahrenheit (celciusValue : real);
fahrenheitValue : real;
begin
fahrenheitValue := 9 / 5 * celciusValue + 32;
writeln('Temperature in Celsius: ', celciusValue:0:2);
writeln('Temperature in Fahrenheit: ', fahrenheitValue:0:2);
end; (* Procedure celciusToFahrenheit *)

105. Procedures: Putting Together The Case With Parameters
A compilable version of this example can be found in Unix under /home/231/examples/functions/temperatureConverter.p
program temperatureConverter (input, output);
var
celciusValue : real;
procedure celciusToFahrenheit (celciusValue : real);
fahrenheitValue : real;
begin
fahrenheitValue := 9 / 5 * celciusValue + 32;
writeln('Temperature in Celsius: ', celciusValue:0:2);
writeln('Temperature in Fahrenheit: ', fahrenheitValue:0:2);
end; (* Procedure celciusToFahrenheit *)
Procedure definition

106. Procedures: Putting Together The Case With Parameters (2)
begin
writeln;
writeln('This program will convert a given temperature from a Celsius's);
writeln('value to a Fahrenheit value.');
write('Input temperature in Celsius: ');
readln(celciusValue);
celciusToFahrenheit(celciusValue);
writeln('Thank you and come again.');
end. (* Program *)

107. Procedures: Putting Together The Case With Parameters (2)
begin
writeln;
writeln('This program will convert a given temperature from a Celsius's);
writeln('value to a Fahrenheit value.');
write('Input temperature in Celsius: ');
readln(celciusValue);
celciusToFahrenheit(celciusValue);
writeln('Thank you and come again.');
end. (* Program *)
Procedure call

108. How Retain Information From A Module After The Module (Function Or Procedure) Has Ended (2)
e.g., producing an income statement
program taxes (input, output);
var
(* Assume declarations made *)
begin
calculateGrossProfit (grossSales);
: :
calculateGrossProfit (grossSales: real);
var
(* Assume declarations made *)
begin
grossProfit := grossSales – costOfGoodsSold;
end; ☼

109. Defining Functions Syntax: Example:
function name (Name of parameter 1 : type of parameter 1;
Name of parameter 2 : type of parameter 2;
: :
Name of parameter n : type of parameter n):
return type;
begin
(* Statements of the function go here *)
: :
name := expression; (* Return value *)
end;
Example:
function calculateGrossIncome (grossSales, costOfGoodsSold : real) : real;
calculateGrossIncome := grossSales - costOfGoodsSold;
Should be the last statement in the function

110. Functions: Putting It All Together
A compilable version of this example can be found in Unix under /home/231/examples/functions/financialStatements.p
program financialStatments (input, output);
function calculateGrossIncome (grossSales, costOfGoodsSold : real) : real;
begin
calculateGrossIncome := grossSales - costOfGoodsSold
end;
function calculateNetIncome (grossIncome, expenses : real) : real;
calculateNetIncome := grossIncome - expenses;
Function definitions

111. Functions: Putting It All Together (2)
procedure produceIncomeStatement;
var
grossSales : real;
costOfGoodsSold : real;
grossIncome : real;
expenses : real;
netIncome : real;
begin
write('Input gross sales $');
readln(grossSales);
write('Input cost of the goods that were sold $');
readln(costOfGoodsSold);
write('Input corporate expenses $');
readln(expenses);
grossIncome := calculateGrossIncome (grossSales, costOfGoodsSold);
netIncome := calculateNetIncome (grossIncome, expenses);
Function calls

112. Functions: Putting It All Together (3)
(* Procedure produceIncomeStatement *)
writeln;
writeln('Gross sales $':26, grossSales:0:2);
writeln('Less: cost of goods sold $':26, costOfGoodsSold:0:2);
writeln('Gross income $':26, grossIncome:0:2);
writeln('Less: expenses $':26, expenses:0:2);
writeln('Net income $':26, netIncome:0:2);
end; (* End of procedure produceIncomeStatement *)

113. Functions: Putting It All Together (3)
(* Start of program *)
begin
writeln;
writeln('This program will produce an income statement based upon your');
writeln('gross sales figures, the cost of the goods that you sold and
writeln('your expenses.');
produceIncomeStatement;
writeln('Thank you, come again!');
end. (* End of entire program. *)

114. Procedure Definitions When Passing Parameters As Variable Parameters
Syntax:
procedure name (var Name of parameter 1 : type of parameter 1;
var Name of parameter 2 : type of parameter 2;
: :
var Name of parameter n : type of parameter n);
begin
(* Statements of the function go here *)
end;
Example:
procedure tabulateIncome ( grossSales : real;
costOfGoodsSold : real;
var grossIncome : real;
expenses : real;
var netIncome : real);
grossIncome := grossSales - costOfGoodsSold;
netIncome := grossIncome - expenses;

115. Calling Procedures With Variable Parameters
Same as calling procedures with value parameters!
Syntax:
name (name of parameter 1, name of parameter 2…name of parameter n);
Example:
tabulateIncome(grossSales,costOfGoodsSold,grossIncome,expenses,
netIncome);

116. Passing Variable Parameters: Putting It All Together
A compilable version of this example can be found in Unix under /home/231/examples/functions/financialStatements2.p
program financialStatments (input, output);
procedure getIncomeInformation (var grossSales : real;
var costOfGoodsSold : real;
var expenses : real);
begin
write('Input gross sales $');
readln(grossSales);
write('Input the cost of the goods that were sold $');
readln(costOfGoodsSold);
write('Input business expenses $');
readln(expenses);
end; (* End of procedure getIncomeInformation *)

117. Passing Variable Parameters: Putting It All Together (2)
procedure tabulateIncome ( grossSales : real;
costOfGoodsSold : real;
var grossIncome : real;
expenses : real;
var netIncome : real);
begin
grossIncome := grossSales - costOfGoodsSold;
netIncome := grossIncome - expenses;
end; (* End of procedure tabulateIncome *)
procedure displayIncomeStatement (grossSales : real;
grossIncome : real;
netIncome : real);

118. Passing Variable Parameters: Putting It All Together (3)
(* Procedure displayIncomeStatement *)
begin
writeln;
writeln('INCOME STATEMENT':40);
writeln('Gross sales $':40, grossSales:0:2);
writeln('Less: Cost of the goods that were sold $':40, costOfGoodsSold:0:2);
writeln('Equals: Gross Income $':40, grossIncome:0:2);
writeln('Less: Business Operating Expenses $':40, expenses:0:2);
writeln('Equals: Net income $':40, netIncome:0:2);
end; (* End of procedure displayIncomeStatement *)
procedure produceIncomeStatement;
var
grossSales, grossIncome, costOfGoodsSold, expenses, netIncome :real;

119. Passing Variable Parameters: Putting It All Together (3)
begin
getIncomeInformation(grossSales, costOfGoodsSold, expenses);
tabulateIncome(grossSales,costOfGoodsSold,grossIncome,expenses,netIncome);
displayIncomeStatement (grossSales,costOfGoodsSold,grossIncome,expenses,netIncome);
end;
(* Begin main program *)
writeln;
writeln('This program will produce an income statement based upon your');
writeln('gross sales figures, the cost of the goods that you sold and');
writeln('your expenses.');
produceIncomeStatement;
writeln('Thank you, come again!');
end. (* End of main program *)

120. POINTERS Types Of Variables
Pascal Variables
1.Data
2. Addresses (pointers)
a. Simple (atomic)
b. Aggregate (composite)
integer
char
boolean
real
Homogenous(arrays)
Heterogeneous(records)

121. Declaration Of Pointer Variables
Syntax:
type
type name = ^ type pointed to1;
var
pointer name : type name;
Example:
IntegerPointer = ^integer;
numPtr1, numPtr2 : integerPointer;
num : integer;
1 You can also use the instead of the “up-arrow” ^ to declare a pointer variable

122. Allocating Memory For Pointers
Static vs. dynamic memory
e.g., array
Allocating memory Deallocating memory
Syntax Syntax
new (pointer name); dispose (pointer name);
Example Example
new (numPtr1); dispose (numPtr1);

123. Allocating Memory For Pointers
Static vs. dynamic memory
e.g., array
Allocating memory Deallocating memory
Syntax Syntax
new (pointer name); dispose (pointer name);
Example Example
new (numPtr1); dispose (numPtr1);
Syntax:
pointer name := NIL;
Example
numPtr1 := NIL;

124. Using Pointers : Assignment
Syntax:
(Pointer)
pointer name := pointer name;
(Memory pointed to)
pointer name ^ := expression;
Example:
numPtr1 := numPtr2;
numPtr1^ := 100;

125. Using Pointers : Allowable Operations (Equity)
Syntax:
(Pointer)
if (pointer name 1 = pointer name 2) then
(Memory pointed to)
if (pointer name 1 ^ = pointer name 2 ^) then
Example:
if (numPtr1 := numPtr2) then
if (numPtr1 ^ := numPtr2 ^) then

126. Using Pointers : Allowable Operations (Inequity)
Syntax:
(Pointer)
if (pointer name 1 <> pointer name 2) then
(Memory pointed to)
if (pointer name 1 ^ <> pointer name 2 ^) then
Example:
if (numPtr1 <> numPtr2) then
if (numPtr1 ^ <> numPtr2 ^) then

127. Accessing Pointers Syntax: Example: (Pointer) pointer name
(Memory pointed to)
pointer name ^
Example:
numPtr1 := numPtr 2;
writeln(numPtr1^);

128. Pointers : First Example
A full version of this example can be found in Unix under: /home/231/examples/pointers/pointer1.p
program pointer1 (output);
type
IntegerPointer = ^integer;
var
num, temp : integer;
numPtr1, numPtr2 : integerPointer;
begin
writeln('Example One');
num := 10;
new(numPtr1);
new(numPtr2);
numPtr1^ := 100;
numPtr2^ := 100;

129. Pointers : First Example (2)
writeln('num = ':11, num:3);
writeln('numPtr1^ = ':11, numPtr1^:3);
writeln('numPtr2^ = ':11, numPtr2^:3);
if (numPtr1 = numPtr2) then
writeln('numPtr1 and numPtr2 point to the same location in memory')
else
writeln('numPtr1 and numPtr2 point to two separate locations');
if (numPtr1 ^= numPtr2^) then
writeln('Value of what numPtr1 and numPtr2 point to are equal.')
writeln('Value of what numPtr1 and numPtr2 point to are equal.');
writeln('Example two');
temp := num;
num := numPtr1^;

130. Pointers: First Example (3)
writeln('Example three');
numPtr1^ := num;
num := 2;
writeln('num = ':11, num:3);
writeln('numPtr1^ = ':11, numPtr1^:3);
writeln('Example four');
numPtr2 ^ := 66;
numPtr1 := numPtr2;
if (numPtr1 = numPtr2) then
writeln('numPtr1 and numPtr2 point to the same location in memory')
else
writeln('numPtr1 and numPtr2 point to two separate locations');
numPtr2^ := 33;
writeln('numPtr1^ = ':11, numPtr1^);
writeln('numPtr2^ = ':11, numPtr2^);

131. Pointers: First Example (4)
dispose(numPtr1);
dispose(numPtr2);
numPtr1 := NIL;
numPtr2 := NIL;

132. Pointers As Value Parameters
Need to define a type for the pointer first!
E.g.,
type
CharPointer = ^char;
Syntax:
procedure procedure name (pointer name (1) : type of pointer (1);
pointer name (2) : type of pointer (1);
: :
pointer name (n) : type of pointer (n));
function function name (pointer name (1) : type of pointer (1);
Example:
procedure proc1 (charPtr : CharPointer);

133. Pointers As Variable Parameters
Need to define a type for the pointer first!
E.g.,
type
CharPointer = ^char;
Syntax:
procedure procedure name (var pointer name (1) : type of pointer (1);
var pointer name (2) : type of pointer (1);
: :
var pointer name (n) : type of pointer (n));
Example:
procedure proc2 (var charPtr : CharPointer);

134. Returning Pointers From Functions
Need to define a type for the pointer first
E.g.,
type
CharPointer = ^char;
Syntax:
function function name: function return type;
begin
function name := expression;
end;

135. Returning Pointers From Functions (2)
Example:
function fun: CharPointer;
var
temp : CharPointer;
begin
new(temp);
temp^ := '#';
fun := temp;
end;

136. Pointers: Second Example
A full version of this program can be found in Unix under: /home/231/examples/pointers/pointer2.p
program pointer2 (output);
type
CharPointer = ^char;
procedure proc1 (charPtr : CharPointer);
var
temp : CharPointer;
begin
writeln;
writeln('In procedure proc1');
new(temp);
temp^ := 'A';
charPtr := temp;
writeln('temp^ = ', temp^);
writeln('charPtr^ = ', charPtr^);
end;

137. Pointers: Second Example (2)
procedure proc2 (var charPtr : CharPointer);
var
temp : CharPointer;
begin
writeln;
writeln('In procedure proc2');
new(temp);
temp^ := 'A';
charPtr := temp;
writeln('temp^ = ', temp^);
writeln('charPtr^ = ', charPtr^);
end;

138. Pointers: Second Example (3)
function fun: CharPointer;
var
temp : CharPointer;
begin
new(temp);
temp^ := '#';
fun := temp;
end;

139. Pointers: Second Example (4)
begin (* Main program *)
var charPtr : CharPointer;
new (charPtr);
charPtr^ := 'a';
writeln;
writeln('In the main program.');
writeln('charPtr^ = ', charPtr^);
proc1(charPtr);
writeln('After proc1');
proc2(charPtr);
writeln('After proc2');
charPtr := fun;
writeln('After fun');
end. (* End of main program *)

140. LINKED LISTS More complex coding may be required
Some list management functions are more elegant (and faster)
Data
Ptr
Data
Ptr
Node
Link List

141. Some Link List Functions
Declaring a link list
Creating a new list
Traversing the list
Adding a node to the list
Searching the list
Deleting a node from the list
Note: These list functions will be illustrated by portions of an example program. This program is the investors program but implemented as a link list rather than as array. The complete program can be found in Unix under: /home/231/examples/link_lists/investors.p

142. Declaring A Link List Syntax: type
Name of the list data = Type of the list data;
Name of the list pointer = ^ Node;
Node = Record
data : Name of the list data;
nextPointer : Name of the list pointer;
Name of link list = Name of list pointer;

143. Declaring A Link List (2)
Example:
type
Client = record
firstName : array [1..NAMELENGTH] of char;
lastName : array [1..NAMELENGTH] of char;
income : real;
array [1.. LENGTH] of char;
end; (* Declaration of record Client *)
ListData = Client;
ListPointer = ^ Node;
Node = record
data : ListData;
nextPointer : ListPointer;
end; (* Declaration of record Node *)
ClientList = ListPointer;

144. Creating A New List Algorithm: Example:
The pointer to the beginning of the list is passed into the procedure as a variable parameter and initialized to NIL signifying that the new list is empty.
Example:
procedure createNewList (var tamjClientList : ClientList);
begin
tamjClientList := NIL;
end; (* Procedure *)

145. Traversing The List Algorithm: Steps
1. Start by initializing a pointer to the beginning of the list.
2. If the pointer is NIL then show message indicating that there
are no nodes to display and stop.
3. Process the node.
4. Move on to the next node by following the node's nextPointer (set pointer to point to the next node).
5. Repeat 3 – 4 until the end of the list is reached (pointer is NIL).

146. Traversing The List (2) Example:
procedure displayList ( tamjClientList : ClientList);
var
currentNode : ListPointer;
begin
currentNode := tamjClientList;
writeln('CLIENT LIST':20);
if (currentNode = NIL) then
writeln;
writeln('List is empty, no clients to display');
end; (* if-then *)

147. Traversing The List (3) while (currentNode <> NIL) do begin
writeln('First name: ':20, currentNode^.data.firstName);
writeln('Last Name: ':20, currentNode^.data.lastName);
writeln('Income $':20, currentNode^.data.income:0:2);
writeln(' ':20, currentNode^.data. );
writeln;
currentNode := currentNode^.nextPointer;
end; (* while *)
end; (* displayList *)

148. Adding A Node To The The List
Algorithm:
Steps
1. Assign a pointer to the front of the list.
2. If the pointer is NIL then the list is empty and add the node to the
front of the list and stop.
3. Otherwise traverse the list with two pointers, one pointer (current pointer) goes to the end of the list, the other stays one node behind it
(previous pointer).
4. Attach the new node to the last node in the list (the one reached by
the previous pointer).
5. The next pointer of the new node becomes NIL (indicating that this
is the end of the list).

149. Adding A Node To The List (2)
Example:
procedure addToList (var tamjClientList: ClientList;
newNode : ListPointer);
var
currentNode : ListPointer;
previousNode : ListPointer;
begin
(* Empty list add new node to front *)
if (tamjClientList = NIL) then
tamjClientList := newNode;
newNode^.nextPointer := NIL;
end

150. Adding A Node To The List (3)
else
begin
currentNode := tamjClientList;
while (currentNode <> NIL) do
previousNode := currentNode;
currentNode := currentNode^.nextPointer;
end; (* while *)
previousNode^.nextPointer := newNode;
newNode^.nextPointer := NIL;
end; (* else *)
end; (* Procedure *)

151. Searching The List Algorithm:
The procedure is run in order to find a node(s) that has a field which
matches some desire value. Either the node or nodes will be found in the list or else the procedure will have searched every node in the list and have found no matches. A flag will be set to true or false indicating the success or failure of the search.
Variables
There are two pointers to the list:
a. Current pointer – traverses the list from beginning to end
b. Previous to first pointer – points to the node that occurs just prior to the
first successful match.
Note: The second pointer does not directly come into play when the user only wants to search the list. They are essential when the person wishes to erase a node from the list. Since the erase procedure calls the search procedure, it is is passed in but it's value is not used when the person just wishes to perform a search without performing a deletion.
2. A boolean that indicates the status of the search.

152. Searching The List (2) Steps
Current pointer starts at the beginning of the list. Since the search has not yet begin, previous is set to NIL and the flag is set to false.
A check is performed to determine if the node is a match. If this is the case and the flag is still false (indicating that we haven't found a previous node that was a successful match) set the flag to true (since a match was found). Since the search function requires a list of all matches (and not just the first instance) don't stop searching the list.
If the flag is set to false then set the previous pointer to point to the current node. If the flag is set to true then don't change the value of flag (the previous pointer tracks the node just prior to the node which first meets the search criteria).
Move on to the next node (by setting the current pointer to the current node's next pointer).
Continue step 2 – 4 until the end of the list is reached (current node is NIL).

153. Searching The List (3) Example:
procedure search ( tamjClientList : ClientList;
desiredName : NameArray;
var isFound : boolean;
var previousFirst : ListPointer );
var
currentNode : ListPointer;
begin
currentNode := tamjClientList;
previousFirst := NIL;
isFound := False;

154. Searching The List (4) while (currentNode <> NIL) do begin
if (desiredName = currentNode^.data.lastName) then
writeln('Found contact':20);
writeln('First name :':20, currentNode^.data.firstName);
writeln('Last name :':20, currentNode^.data.lastName);
writeln('Income $':20, currentNode^.data.income:0:2);
writeln(' ':20, currentNode^.data. );
writeln;
if (isFound = False) then
isFound := True;
end; (* if-then *)

155. Searching The List (5) if (isFound = False) then
previousFirst := currentNode;
currentNode := currentNode^.nextPointer;
end; (* while *)
writeln('Contact not found in list');
end; (* search *)

156. Deleting A Node From The List
Algorithm:
Steps
Search the list (by calling the search procedure) to determine if there exists a node that matches the necessary criteria for deletion.
Check the flag to determine if the search was successful or not. If the flag is false then there is no matching node in the list. Stop. There is no matching node to delete.
Check to see if the node to be deleted is the first node in the list or not by determining if the previous node is NIL.
If the node to be deleted is the first node then have a temporary pointer point to the first element and make the front of the list the second element.
If the node to be deleted is not the first node then have a temporary pointer point to the node to be deleted. Set the next pointer of the previous node point to the node after the node to be deleted (bypassing this node)
For steps 4 & 5 free up the memory allocated by the node to be deleted.

157. Deleting A Node From The List (2)
Example:
procedure erase (var tamjClientList : ClientList );
var
desiredName : NameArray;
previousFirst : ListPointer;
temp : ListPointer;
isFound : boolean;
begin
write('Enter last name of client to delete: ');
readln(desiredName);
search (tamjClientList, desiredName, isFound, previousFirst);
if (isFound = True) then
writeln('Deleting first instance of ', desiredName);
if (previousFirst = NIL) then

158. Deleting A Node From The List (3)
begin
writeln('Deleting first instance of ', desiredName);
if (previousFirst = NIL) then
temp := tamjClientList;
tamjClientList := tamjClientList^.nextPointer;
end (* if-then *)
else
temp := previousFirst^.nextPointer;
previousFirst^.nextPointer := temp^.nextPointer;
end; (* else *)
dispose(temp);
end; (* if-then *)
end; (* Procedure *)