MODULAR DESIGN

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• MODULAR DESIGN
• AND ABSTRACTION

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• SPECIFYING THE DETAILS OF A PROBLEM
• INTO A RELATED SET OF SMALLER
• PROBLEMS.

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TOP- DOWN DESIGN

• STATE THE PROBLEM
• SUBDIVIDE THE PROBLEM INTO MAJOR SUBPROBLEMS
• SUBDIVIDE EACH SUBPROBLEM INTO SMALLER TASKS
• REPEAT THE PROCESS UNTIL TASKS ARE EASILY
• SOLVED.

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THE STRUCTURE CHART
A GRAPHICAL REPRESENTATION OF SYSTEM COMPONENTS.
USED TO IDENTIFY AND DEFINE RELATIONSHIPS AMONG
SUBPROBLEMS.
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A STRUCTURE CHART
main
LEVEL O
LEVEL 1
module1
module3
module2
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STEPWISE REFINEMENT

• EACH SUBDIVISION IS REFERRED TO AS A
• STEPWISE REFINEMENT.
• TASKS AT EACH STAGE OF THE SUBDIVISION ARE
• REFERRED TO AS MODULES.

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PROBLEM SOLVING WITHTOP- DOWN DESIGN

• PROBLEM
• GET THREE INTEGER NUMBERS REPRESENTING
• TEST MARKS. COMPUTE AND DISPLAY THEIR AVERAGE.

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THE STRUCTURE CHART FOR PROGRAM FindAvg
FindAvg
LEVEL 0
LEVEL 1
Get Numbers
Display Results
Calculate Average
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THE ALGORITHM

• 1 GET test1, test2, test3
• 2 CALCULATE average
• 3 DISPLAY average

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NEW CONCEPTS
MODULES
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MODULAR DESIGN ANDFUNCTIONS
MODULES ARE CODED AS SUBPROGRAMS. A C
FUNCTION IS A GROUPING OF STATEMENTS INTO A
SINGLE UNIT THAT PERFORMS A TASK. EACH C
PROGRAM IS MADE UP OF ONE OR MORE FUNCTIONS
(main() IS A FUNCTION).
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FUNCTION PROTOTYPE
A FUNCTION MUST BE DECLARED BEFORE IT MAY BE
CALLED.
type function_name ()
// FINDS THE AVERAGE OF THREE NUMBERS void
Find_average ()
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FUNCTION CALLS
A FUNCTION IS CALLED THROUGH THE EXECUTION OF A
FUNCTION CALL. LOGIC FLOW IS TRANSFERRED TO
function_name.
function_name ()
// A CALL TO FUNCTION Find_average Find_average
()
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FUNCTION DEFINITION
A FUNCTION CONSISTS OF 2 PARTS THE HEADING AND
THE BODY. THE HEADING INCLUDES A TYPE
SPECIFICATION, FUNCTION NAME, AND LEFT AND RIGHT
PARENTHESES. THE BODY CONSISTS OF LOCAL
DECLARATIONS AND EXECUTABLE STATEMENTS. THE
FUNCTION BODY BEGINS WITH A LEFT BRACE AND ENDS
WITH A RIGHT BRACE.
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type function_name ( ) local_declarations execut
able_statements
heading
body
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EXAMPLE
void Find_average() // Calculates the
average const int NUMBER_OF_TESTS 3
average (test1 test2 test3) /
NUMBER_OF_TESTS return // end Find_average
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FLOW OF CONTROL

• FUNCTIONS ARE DEFINED PHYSICALLY AFTER THE MAIN
  PROGRAM. EXECUTION STARTS WITH THE STATEMENTS OF
  THE MAIN PROGRAM.
• THE CALL STATEMENT ACTS AS TRANSFER OF CONTROL.
  THE RETURN STATEMENT SENDS THE CONTROL BACK TO
  THE CALLING MODULE.

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EXAMPLE
... void main () ... Get_data ()
Find_average () Display_results ()
return
void Find_average () // Calculates the
average const int NUMBER_OF_TESTS 3
average ( test1 test2 test3 ) /
NUMBER_OF_TESTS return // end
Find_average ()
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THE CODE FOR FindAvg

• // FILE FindAvg2.cpp
• // Finds the average of three test scores
• include ltiostream.hgt
• // global data
• float test1, test2, test3, average
• void main ()
• // functions used
• void Get_data ()
• void Find_average ()
• void Display_results ()
• // function calls
• Get_data ()
• Find_average ()
• Display_results ()
• return

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void Get_data () // Gets the grade marks
cout ltlt "Enter the three test marks " cin gtgt
test1 gtgt test2 gtgt test3 return void
Find_average() // Calculates the average
const int NUMBER_OF_TESTS 3 average (test1
test2 test3) / NUMBER_OF_TESTS
return void Display_results () //
Displays the average cout ltlt "The average of
the 3 test marks is " ltlt average ltlt endl
return
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LOCAL DECLARATIONS
OBJECTS DECLARED LOCALLY WITHIN A FUNCTION CAN BE
REFERENCED ONLY WITHIN THAT FUNCTION.
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GLOBAL DECLARATIONS
OBJECTS DECLARED OUTSIDE OF FUNCTIONS CAN BE
REFERENCED FROM WITHIN ANY FUNCTION THAT FOLLOWS
THAT DECLARATION.
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MODULE COMMUNICATION

• PARAMETERS ARE USED TO COMMUNICATE BETWEEN
  MODULES.
• THE CALLING MODULE PASSES VALUES TO THE CALLED
  MODULE TO USE THEM IN PROCESSING.
• THE CALLED MODULE RETURNS THE RESULTS TO THE
  CALLING MODULE.

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Flow of control in the program 24
1-?Execution starts from the beginning of the
program and reaches the statement
2-4?func is called. Param, temFarenheit,
evaluated, copied into tempFahr. Then control is
transferred to called function.
5? execution in the called function
6 - 7? return type is double and assigned to
tempCelsius
8 ?Execution follow normally in the main.
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EXAMPLE
PROBLEM GIVEN THE RADIUS OF A CIRCLE, COMPUTE AND
DISPLAY THE AREA AND THE CIRCUMFERENCE.
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ANALYSIS AND SPECIFICATIONS IN ORDER TO COMPUTE
THE CIRCLES AREA AND CIRCUMFERENCE (PROBLEMS
OUTPUT), WE NEED THE RADIUS (PROBLEMS INPUT).
WE ALSO KNOW THAT THE AREA MAY BE CALCULATED AS
p x RADIUS2 AND THE CIRCUMFERENCE MAY BE
CALCULATED AS 2 x p x RADIUS. DATA
REQUIREMENTS CONSTANT p 3.14159 INPUT
RADIUS (FLOAT) OUTPUT AREA (FLOAT)
CIRCUMFERENCE (FLOAT) FORMULAE AREA
p RADIUS RADIUS
CIRCUMFERENCE 2 p RADIUS
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DESIGN HAVING DEFINED THE PROBLEMS INPUT AND
OUTPUT, WE MAY START IDENTIFYING THE SYSTEMS
COMPONENTS AND STEPS NECESSARY TO SOLVE THE
PROBLEM.
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STRUCTURE CHART
AreaCircm
LEVEL 0
LEVEL 1
Get radius
Display Result
Compute
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STRUCTURE CHART
AreaCircm
LEVEL 0
LEVEL 1
Get radius
Display Result
Compute
area
circum
LEVEL 2
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ALGORITHM
1. GET DATA 2. COMPUTE 3. DISPLAY RESULTS
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ALGORITHM A Second Level Refinement
1. GET DATA 2. COMPUTE 2.1 COMPUTE AREA 2.2
COMPUTE CIRCUMFERENCE 3. DISPLAY RESULTS
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NEW CONCEPTS
MODULES COMMUNICATION
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FUNCTION PROTOTYPEUSING PARAMETERS
type function_name (parameter_type_list)
// computes the area of a circle float
Compute_area (float r)
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FUNCTION CALLS
function_name (parameter_list)
// A call to function Compute_area() Compute_area
(radius)
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FUNCTION DEFINITIONUSING PARAMETERS
type function_name ( parameter_list) local_decla
rations executable statements
heading
body
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EXAMPLE
DEFINITION
// computes the area of a circle float
Compute_area (float r) // compute and return
the area return PI r r // end
Compute_area ()
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CALL
area Compute_area (radius)
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NAMING RULES

• SAME RULES AS WITH IDENTIFIERS.
• void Module_name (float first, float second,
• float third, float result)
• OR
• void Calculate_average (float test1, float test2,
• float test3, float
  average)
• THE SECOND MODULE NAME IS MORE MEANINGFUL.

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IMPLEMENTATION FOR AreaCircm
// FILE AreaCircm.cpp // FINDS AND PRINTS THE
AREA AND CIRCUMFERENCE OF A CIRCLE include
ltiostream.hgt include "CmptArCr.cpp"
//Compute_area and Compute_circum void main
() // functions used // COMPUTES THE AREA
OF A CIRCLE float Compute_area (float) //
COMPUTES THE CIRCUMFERENCE OF A CIRCLE float
Compute_circum (float) // local data float
radius // radius of circle float
area // area of circle float
circum // circumference of circle
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// get radius cout ltlt "enter the circle
radius " cin gtgt radius // compute the
area of the circle area Compute_area
(radius) // compute the circumference of the
circle circum Compute_circum (radius)
cout ltlt "the area of the circle is " ltlt area ltlt
endl cout ltlt "the circumference of the circle
is " ltlt circum ltlt endl return
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// FILE CmptArCr.cpp // Modules to calculate the
area and // circumference of a circle. // global
data const float PI 3.14159 // COMPUTES THE
AREA OF A CIRCLE float Compute_area (float r)
// compute and return the area return PI r
r // end Compute_area ()
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// COMPUTES THE CIRCUMFERENCE OF A CIRCLE float
Compute_circum (float r) // compute and
return the circumference return 2.0 PI r
// end Compute_circum ()
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ACTUAL PARAMETERS

• THE PARAMETERS IN THE CALL STATEMENT ARE
  REFERRED TO AS ACTUAL PARAMETERS. THE VALUE OF AN
  ACTUAL PARAMETER IS PASSED AND USED BY THE
  FUNCTION.

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FORMAL PARAMETERS
THE PARAMETERS IN THE FUNCTION HEADING ARE
REFERRED TO AS FORMAL PARAMETERS. A FORMAL
PARAMETER REPRESENTS THE ACTUAL VALUE PASSED TO
THE FUNCTION EACH TIME IT IS CALLED.
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LIBRARIES OF FUNCTIONS
PROVIDE ACCESS TO PREVIOUSLY WRITTEN FUNCTIONS
THAT PERFORM USEFUL DIAGNOSTICS, MANIPULATIONS,
COMPUTATIONS, ETC.
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EXAMPLES OF SOMEMATHEMATICAL FUNCTIONS

• result sqrt (16) 10
• RETURNS THE VALUE 40.0. THE SQUARE ROOT
• OF 16 IS CALCULATED, THEN THE VALUE
• IS MULTIPLIED BY 10.
• floor (3.8) 3
• RETURNS THE LARGEST INTEGER NOT GREATER THAN THE
  PARAMETER.
• fabs (-3.8) 3.8
• RETURNS THE ABSOLUTE VALUE.

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// computes the area of a circle float
Compute_area (float r) // compute and return
the area return PI r r // end
Compute_area ()
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FILE INPUT/OUTPUT

• DATA IS OFTEN PREPARED AND STORED INTO A FILE.
• WHEN THE PROGRAM EXECUTES, IT ACCESSES
• THE FILE TO READ THE DATA.
• THE RESULTS ARE WRITTEN TO THE SCREEN OR TO AN
  OUTPUT FILE.

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• I/O FILES IN C PROGRAMS

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• CIS113
• Assignment 2
• Implement and document a program that has the
  following Behavior
• Your program should
• display on the screen a prompt for a Fahrenheit
  temperature.
• The user will enter numeric value from the
  keyboard, which the program will read.
• The will compute the Celsius temperature
  equivalent to that Fahrenheit, and
• display this Celsius temperature on the screen
  along with descriptive text

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• A- Determine if each is a valid C identifier.
  If it is not, give a reason.
• 1- XRay 2- Jeremiah 3- X 4- nite 5- to day
• B- Classify each as an integer literal, a real
  literal, or neither. If it is neither, give a
  reason.
• 1- 12 2- 3.98 3- 24E0 4- 0E0
• C- Determine if each is a valid string literal,
  If it is not, give a reason.
• 1- X 2- 123 3- \twas
• D- Write constant declarations to associate each
  name with the specified literal.
• 1- 1.25 with the name RATE
• 2- 1776 with the name YEAR , the letter F with
  FEMALE, and a blank character with BLANK.