Pascal 1 Week 9 Day 1

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Pascal 1 Week 9 Day 1

• Procedures Day 1

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Program Song procedure Chorus begin
writeln(Oh, I dont care too much for Army
life!) writeln(Gee Mom, I wanna go back
where the roses grow) writeln(But they
wont let me go home.) end procedure
FirstVerse begin write(They say that I the
Army) writeln( the coffees mighty
fine.) write(Its good for cuts and
bruises,) writeln( and tastes like
iodine.) end procedure SecondVerse begin
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.) end begin Of the
main body FirstVerse Chorus writeln Second
Verse Chorus end.
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Procedures and Functions

• What are they?
• Subprograms Like GOSUBs in BASIC but with
  greater power.
• If it returns only one value use a function,
  otherwise use a procedure

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Why are they needed?

• 1)       As your programs grow longer and longer
  they become more difficult to read. Procedures
  and functions allow you to break your program
  into smaller programs.
• 2)       Allow you to work in groups on a program
  and have each member of the group write a section
  of code (procedure/function) and you can piece it
  together more easily.
• 3) Allow for recursion.

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Where are they located?

• Procedures and functions go in between the VAR
  declarations and the BEGIN of the main body.

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How does it work?

• It takes three parts to make a subroutine
• The Call Statement
• The Header
• The Code

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The Call Statement

• This calls the subroutine into action by using
  the subroutine name and sends information through
  the argument list (More on this later.) In the
  previous example, all of the call statements were
  in the main body. (FirstVerse Chorus)
• For the rest of today we will focus on Procedures
  and hit functions later.

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Calling Procedures

• ProcedureName(ArgumentList)
• Argument List Contains variables, values and
  expressions, separated by commas, that are sent
  to the subroutine and variables that save answers
  found in the subroutine. (More Later)

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Sample Procedure call statements
Procedure name
Argument List

• FirstVerse
• Field(Money)
• Show(money,Game, Bet, Roll, Win, Newbal)
• Chorus
• Deposit(Savings,SavingsBalance,amount)
• Play(song, 5)
• DoubleEm(total, 28)

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The Header

• This defines the name of the subroutine and the
  name and types of the variables sent to the
  subroutine (parameter list).

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Procedure Procedurename(ParameterList)

• Procedure This is a reserved word and it tells
  the computer you are starting a procedure.
• ProcedureName This is an identifier name,
  following the same rules as those for variables.
  This is the exact name the must be used in the
  call statement.

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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.

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Sample Headers

• Procedure Chorus
• Procedure FirstVerse

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Quick Review

• Subroutines are like mini programs
• Subroutines have three parts
• Call statement
• Name(Arguments)
• Header
• Procedure Name(Parameterstypes)
• Code

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The Code

• Locally declared variables
• Can include const, type, and var declarations
• The variables only exist while the subroutine is
  running
• Can use all the constructs
• Can call other subroutines that are declared
  above the subroutine

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Adding vocab. to the example
Program Song procedure Chorus begin
writeln(Oh, I dont care too much for Army
life!) writeln(Gee Mom, I wanna go back
where the roses grow) writeln(But they
wont let me go home.) end procedure
FirstVerse begin write(They say that I the
Army) writeln( the coffees mighty
fine.) write(Its good for cuts and
bruises,) writeln( and tastes like
iodine.) end procedure SecondVerse begin
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.) end begin Of the
main body FirstVerse Chorus writeln Second
Verse Chorus end.
Header
Code
Call Statement
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Program Options

• 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)
• Write procedures to draw a person doing jumping
  jacks. A separate procedure for each position and
  cycle through the positions with a loop.