Modules – the Basics

Modules – the Basics CSCE 110 Influenced by material developed by James Tam & Jennifer Welch

Header Declarations const : Statements begin end. Where To __________ Modules Module ________ (___________ & ____________)

Procedure definition Procedures (Basic Case) Procedure call No Information Is Passed In/ No Parameters

Defining Procedures (Basic Case – No __________) Format: procedure name; begin { Statements of the procedure go here } end; { End of procedure name } Example: procedure displayInstructions; begin writeln ('The statements in this module will'); writeln (' typically give a high level'); writeln (' overview of what the program as a'); writeln ('whole does'); end; (* End of procedure displayInstructions *)

Calling A Procedure (Basic Case – No __________) Format: name; Example: displayInstructions; The name of the procedure is a ____________.

Where To ______ Modules It can be done ________________________ in the program – but must be done ___________ its ____________. Header Declarations const : Modules can be ______ from the ______________ of the program or from within any _______ as long as the __________ is already ___________. Module definitions Main Body begin end.

Correct First: _______ the module Second: _______ the module Important: A Module Must Be ________ Before It Can Be ___________! program exampleModule (output); procedure exampleProcedure; begin : end; begin exampleProcedure; end.

Incorrect First: ________ the module Code? Second: ____________ the module Important: A Module Must Be ________ Before It Can Be ________! program exampleModule (output); begin exampleProcedure; end. procedure exampleProcedure; begin : end;

Procedures firstExampleProcedure.pas program firstExampleProcedure (output); procedure displayInstructions; begin writeln ('The statements in this module will typically give a’); writeln (‘high level overview of what the program as a’); writeln (‘whole does'); end; (*Procedure displayInstructions *) begin displayInstructions; writeln('Thank you, come again!'); end. (* Program *)

Procedures firstExampleProcedure.pas program firstExampleProcedure (output); procedure displayInstructions; begin writeln ('The statements in this module will typically give a’); writeln (‘high level overview of what the program as a’); writeln (‘whole does'); end; (*Procedure displayInstructions *) begin displayInstructions; writeln('Thank you, come again!'); end. (* Program *) Procedure ___________ Procedure ___________

Declaring _______ Variables Format: procedure name; var <variable 1 name> : <variable 1 type>; <variable 2 name> : <variable 2 type>; : : begin : end; Example: procedure proc; var num1 : integer; num2 : integer; begin : : end;

Declaring __________ Variables program secondExampleProcedure (output); procedure proc; var num1 : integer; begin var num2 : integer; num1 := 1; num2 := 2; writeln(num1, ' ', num2); end; begin var num1 : integer; num1 := 10; writeln(num1); proc; writeln(num1); end.

Declaring ________ Variables secondExampleProcedure.pas program secondExampleProcedure (output); procedure proc; var num1 : integer; begin var num2 : integer; num1 := 1; num2 := 2; writeln(num1, ' ', num2); end; begin var num1 : integer; num1 := 10; writeln(num1); proc; writeln(num1); end. ______ variable: procedure ‘proc’ ________ variable: main module

This ________ is __________ here These 4 __________ are _________ to procedure ‘calculateInterest’ ______ Variables Have ____________________ procedure getInformation; begin write (‘Enter the principle: ‘); readln (principle); end; procedure calculateInterest; var amount : integer; principle : integer; interest : integer; time : integer; begin getInformation; end;

pennies dimes amount quarters ___________________ To Modules • Modules generally aren’t useful unless they can ______________________. computeChange

Procedures With ____________________ Passed In Procedure call P1 P2 …Pn Procedure definition

_________Parameters Defining Modules (Procedures) With ____________ Format: 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 procedure go here *) end; Example: procedure celciusToFahrenheit (celciusValue : real); var 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 *)

Calling Modules (Procedures) With Parameters Format: name (Name of parameter 1, Name of parameter 2…Name of parameter n); Example: celciusToFahrenheit (celciusValue); _________Parameters

________ and _________ Parameters • __________ parameters: The parameters in the method _______________. • __________ parameters: The parameters in the method _______________. • Parameters act like _________________ within a module.

____________ and ______________ Parameters • Module call and module definition must have: • _____________ of parameters • ______________ parameters must have the same _______ • e.g. definition:procedure calc(i: integer, f: real, b:boolean);e.g. call:calc(num, avg, flag)where: • _____ must be of type ____________ • _____ must be of type ____________ • _____ must be of type ____________

Procedure definition requires an __________ parameter parameters match Procedure call passes in an __________ parameter Important: The _____ and _____ Parameter Lists Must _____! • The ______ and _________ of parameters must ________ or there will be a compilation error. program parameterExample; procedure proc (num : integer); begin num := 10; end; begin var num : integer; proc (num); end.

Procedure definition requires __________ parameter Number of parameters not equal Procedure call passes in ________parameters Important: The _____ and _____ Parameter Lists Must _____! • The ______ and _________ of parameters must ________ or there will be a compilation error. program parameterExample; procedure proc (num : integer); begin num := 10; end; begin proc; end.

Procedure definition requires an __________ parameter Type mismatch Procedure call passes in a ______ parameter Important: The _____ and _____ Parameter Lists Must _____! • The ______ and _________ of parameters must ________ or there will be a compilation error. • . program parameterExample; procedure proc (num : integer); begin num := 10; end; begin var ch : char; proc (ch); end.

Example Problem Write a program that will convert a temperature value from Celsius to Fahrenheit. The part of the program that performs that actual conversion should take the form of a separate module.

Procedures: Putting Together The Case Of Procedures With Parameters temperatureConverter.pas program temperatureConverter (input, output); procedure celsiusToFahrenheit (celsiusValue : real); var fahrenheitValue : real; begin fahrenheitValue := 9 / 5 * celsiusValue + 32; writeln('Temperature in Celsius: ', celsiusValue:0:2); writeln('Temperature in Fahrenheit: ', fahrenheitValue:0:2); end; (* Procedure celsiusToFahrenheit *)

Procedures: Putting Together The Case Of Procedures With Parameters (2) begin var celsiusValue : real; writeln; writeln('This program will convert a given temperature from a Celsius'); writeln('value to a Fahrenheit value.'); write(‘Enter a temperature in Celsius: '); readln(celsiusValue); writeln; celsiusToFahrenheit(celsiusValue); writeln('Thank you and come again.'); end. (* Program *)

Pass by ______ vs. Pass by __________ • Each _______ parameter is ____________ to the _______ of the corresponding ____________ parameter. Called ________________________.

Pass by ______ vs. Pass by __________ • Let actP be actual and formP be formal • Pass by __________ • actP and formP refer to __________ memory locations • ________ of actP’s______________ to formP’s_______ • changes to formP are __________ to the caller (i.e. actP) • Pass by Reference • actP and formP refer to __________ memory location • the _______ for formP is ____________________ for actP • changes to formP are __________ to the caller (i.e. actP) • By default, Pascal passes variables by ________. However, we’ll see how to make it pass by _________________.

... ... ... k a b c i j ... ... a,i b,j c,k Pass by ______ vs. Pass by __________ • procedure larger(i:integer; j:integer; k:integer);begin if (i<j) then i := j; k := i;end; • Suppose that larger is called with: • a := 3; b := 5; larger(a,b,c); • After calling larger and passing by __________, then a = 3, b = 5, c = 5 • After calling larger if passing by __________, then a = 5, b = 5, c = 5

Module call (local variables get _________ in memory) Module ends (local variables get ____________ in memory) Stack Frames • When a method begins executing, space on the ________, called a _____________, is ____________ for it, to hold • formal parameters • local variables declared in the method • return value (for functions) • When the method finishes __________, the _______ frame is ______________, and the formal parameters and local variables are _______________________. The program code in the module executes (the variables are used to _________________________)

q r p p p p main main main main main main calls p p calls q q returns p calls r s r r p p p main main main main r calls s s returns r returns p returns Stack Frames Example

Modules – the Basics