1. Computer Science
Procedures
Day 2

2. Learning Targets
Review Procedures: 20 minutes time to finish procedure 1 program from December
Know the parts of a procedure header
Be able to recognize a variable and value parameter.
Be able to Dry run a program that uses variable and value parameters
Be able to write a program that uses variable and value parameters

3. Adding vocab. to the example
Program Song;
procedure Chorus;
begin
writeln(‘Oh, I don’’t care too much for Army life!’);
writeln(‘Gee Mom, I wanna go back where the roses grow’);
writeln(‘But they won’’t let me go home.’);
end;
procedure FirstVerse;
write(‘They say that I the Army’);
writeln(‘ the coffee’’s mighty fine.’);
write(‘It’’s good for cuts and bruises,’);
writeln(‘ and tastes like iodine.’);
procedure SecondVerse;
Var
loopy:integer;
Begin
for loopy:= 1 to 3 do
write(‘They say that in the Army, ‘);
writeln(‘the biscuits are real fine.’);
write(‘One rolled off a table, ‘);
writeln(‘ and killed a pal of mine.’);
Header
begin {Of the main body}
FirstVerse;
Chorus;
writeln;
SecondVerse;
end.
Call Statement
Local Variable.
Code

4. 1) Modify the Army song by using a song of your choice or your creation. It must be rated ‘G.’
2) Write a program that uses three procedures to draw a person. Procedures DrawHead (A circle would be fine), DrawBodyAndArms (Lines are fine), and DrawLegs (Lines are fine)
3) Write procedures to draw a person doing jumping jacks. A separate procedure for each position and cycle through the positions with a loop.
Push: Have them run across the screen.
Push: Have a dance team
Push: Have them change direction based on user input.
Program Options

5. Review program DryRunCheck; var a, b:integer;
{*******************************}
procedure first(one, two: integer);
three:integer;
begin
writeln('Hello ');
three:= two - one;
writeln(one:5, two:5, three:5);
end;
{******************************}
begin // Main Body
a:=10;
b:=15;
writeln(a:5,b:5);
first(a,b);
end.
What is the name of the procedure?
Where is the call statement?
Where is the header?
Where is the code for the procedure?
Where is the code for the main body?
What are the local variables for the procedure?
What are the global variables for the program?

6. The Header with Parameter Lists
Get out your notes:
The Header with Parameter Lists
procedure Deposit(account:string; var Balance, amount:real);
The Header defines the name of the procedure and the name and types of the variables sent to the subroutine (parameter list).

7. Procedure Procedurename(ParameterList);
Parameter List: This lists variables, and their types, for ALL information that gets sent to and returned from the procedure.
Note: there is a one-to-one relationship between the parameter list and the argument list.
(Variable:type)
(variable1, variable2:type;variable3:type);
Example:
procedure Deposit(account:string; var Balance, amount:real);
Corresponding call statement from the main body
Deposit(‘Savings’,SavingsBalance,amount);
Note the Punctuation

8. Variable and Value parameters
procedure Deposit(account:string; var Balance, amount:real);
Variable Parameters (Arrow)
Has a var in front of the variable.
Can have commas between variable parameters in the header.
As the variable changes in the procedure, it changes the global variable sent to it.
It is used for getting or changing information in the procedure, adding to a total, etc. Must be sent a variable from the call statement!!!
Value Parameters (Box)
Those that will not change.
Can be sent a variable (x), value (12), or expression (2*b+8).

9. Recognizing Parameters
procedure Instructions(Questn:char; Level:integer);
procedure Field(var Money, bet:real);
procedure Show(money:real; Game:string; Bet:real;
Roll:integer; Win:real; Newbal:real);
procedure Deposit(account:string; var Balance, amount:real);
Variable Parameters:
Can only accept variables
Value Parameter:
Can accept variables, values or expressions

10. Adding vocab. to the example
Program ProcedureExample;
var
num1,num2,difference:integer;
{************************************}
procedure GetTheNumbers(var first, second:integer);
Var
total:integer;
begin
writeln(‘Please enter a number’);
readln(first);
writeln(‘Please enter another number’);
readln(second);
total:= first+second;
Writeln(‘The total = ‘, total);
end;
{**********************************}
begin {Of the main body}
GetTheNumbers(num1, num2);
difference:=num1- num2;
writeln(num1,’ - ‘, num2, ‘ = ‘, difference);
readln;
end. {Of the main body}
Variable Parameters
Header
Arguments
Code
Call Statement

11. Reading a program that has parameters.
program confusion;
var
a, b:integer;
{******************************************************}
procedure one(d, e:integer);
f:integer;
begin
writeln('One ');
f:= d + e;
d:= f + 4;
writeln(d, e, f);
end;
{*****************************************************}
begin // Main Body
a:=5;
b:=6;
writeln(a,b);
one(a,b);
end.
Reading a program that has parameters.
Dry run the following as a class.

12. Dry run the following program confusion2; var a, b:integer;
{******************************************************}
procedure one(var d, e:integer);
f:integer;
begin
writeln('One ');
f:= d + e;
d:= f+4;
writeln(d, e, f);
end;
{*****************************************************}
begin // Main Body
a:=5;
b:=6;
writeln(a,b);
one(a,b);
end.
Dry run the following

13. What do you recall about…
Procedures
Call statements
Headers
Variable parameters
Value parameters
Arguments
Local Variables
Global Variables

14. begin {Of the main body} a:=2; b:=3; c:=4; writeln(a,b,c); d(c,b,a);
program confusion3; //Dry Run
var
a,b,c:integer;
procedure d(a,b:integer; var e:integer);
c:integer;
begin
c:=a+b;
writeln(a,b,c);
e:=c+a;
end;
procedure e(var c:integer; b:integer);
a:integer;
a:=c+b;
begin {Of the main body}
a:=2;
b:=3;
c:=4;
writeln(a,b,c);
d(c,b,a);
e(a,b);
end.

15. begin a:=2; b:=4; c:=6; writeln(a,b,c); one(a,b,c); two(b,a,c); end.
program confusion4; //Dry Run
var
a,b,c:integer;
procedure one(var x, a:integer; y:integer);
b:integer;
begin
b:=a+x+y;
a:=b-x;
writeln(a,b,x,y);
x:=b;
end;
procedure two(x,y:integer; var z:integer);
a:integer;
a:=x+y;
y:=a+y;
z:=a+x;
writeln(a,x,y,z);
begin
a:=2; b:=4; c:=6;
writeln(a,b,c);
one(a,b,c);
two(b,a,c);
end.

16. Developing a program that uses procedures with parameters.
Bubble Diagram
Pascal
Task: “Write a procedure that is sent two integer values, then adds them up and shows the answer inside the procedure”
Start by creating a Bubble Diagram
Up only arrows are Value Parameters
Down arrows are Variable Parameters

17. Developing a program that uses procedures with parameters.
“Modify this so that it will add the numbers in the procedure and show the answer in the main body.”
Start by creating a Bubble Diagram
Up only arrows are Value Parameters
Down arrows are Variable Parameters

18. Take two minutes to Summarize the following in your notes.
Procedure
Header
Call Statement
Variable Parameter
Value Parameter
Bubble Diagram

19. Program Options
Write a program that will have a procedure get 10 numbers and calculate the total and average of the 10 numbers. Then show the total and average in the main body.
Write a program that will get the number of stick figures you would like to display in the main body.
Show that many figures from the procedure
Write a program that will input the real and imaginary parts of two complex numbers in the main body
Add the numbers in a procedure
Show the total in the main body
Example: Input: 5 + 2i, and 2 + 3i it would return 7 + 5i
Note you will need a separate variable for the real and imaginary parts of the number
Push: Create a procedure for multiplying complex numbers.
Push: A procedure for raising a complex number to a positive integer power.