CHAPTER 2 PROBLEM SOLVING

CHAPTER 2
PROBLEM SOLVING
• This chapter will cover the following topics:
– Problem Solving Concepts for the Computer
– Pre-Programming Phase
– Programming Or Implementation Phase
What Problem Can Be Solved By
Computer
• When the solution can be produced by a set of
step-by-step procedures or actions.
• This step-by-step action is called an algorithm.
• The algorithm will process some inputs and
produced output.
• Solving problem by computer undergo two
phases:
– Phase 1:
• Organizing the problem or pre-programming phase.
– Phase 2:
• Programming phase.
PRE-PROGRAMMING PHASE
This phase requires five steps:
1. Analyzing the problem - PAC
2. Developing the Hierarchy Input Process
Output (HIPO) chart or Interactivity Chart
(IC).
3. Developing the Input-Process-Output (IPO)
Chart.
4. Drawing the Program flowcharts.
5. Writing the algorithms.
PRE-PROGRAMMING PHASE
1. Analyzing The Problem
– Understand and analyze the problem to
determine whether it can be solved by a
computer.
– Analyze the requirements of the problem.
– Identify the following:
• Data requirement.
• Processing requirement or procedures that will be
needed to solve the problem.
• The output.
PRE-PROGRAMMING PHASE
• All These requirements can be presented in a
Problem Analysis Chart (PAC)
Data
given in the
problem or
provided by the
user
Processing
List of processing
required or
procedures.
Output
Output
requirement.
PRE-PROGRAMMING PHASE
• Example: Payroll Problem
– Calculate the salary of an employee who works by
hourly basis. The formula to be used is
Salary = Hour works * Pay rate
Data
Processing
Output
Hours work, Salary = Hours work * payrate Salary
Pay rate
Problem 1
Write a Problem Analysis Chart (PAC) to convert
the distance in miles to kilometers where 1.609
kilometers per mile.
Data
Distance in
miles
Processing
Output
Kilometers =
1.609 x miles
Distance in
kilometers
Problem 2
• Write a Problem Analysis Chart (PAC) to find an
area of a circle where area = pi * radius * radius
Data
radius
Processing
area = 3.14 x radius x radius
Output
area
Problem 3
• Write a Problem Analysis Chart (PAC) to compute and display the
temperature inside the earth in Celsius and Fahrenheit. The relevant
formulas are
Celsius = 10 x (depth) + 20
Fahrenheit = 1.8 x (Celsius) + 32
Data
Processing
Output
depth celsius = 10 x (depth) + 20
Display celsius,
fahrenheit = 1.8 x (celsius) + Display
32
fahrenheit
Problem 4
• Write a problem analysis chart (PAC) that
asks a user to enter the distance of a trip
in miles, the miles per gallon estimate for
the user’s car, and the average cost of a
gallon of gas. Calculate and display the
number of gallons of gas needed and the
estimated cost of the trip.
Data
distance,
miles per gallon,
cost per gallon
Processing
gas needed = distance /
miles per gallon.
Output
Display gas needed
Display estimated cost
estimated cost = cost per
gallon x gas needed
Extra Problem
Write a problem analysis chart (PAC)
that asks a user to enter a unit price and
quantity of the product sold . Calculate
and display the total sale
PRE-PROGRAMMING PHASE
• Developing the Hierarchy Input Process
Output (HIPO) or Interactivity Chart (IC)
– The problem is normally big and complex.
– Thus, requires big program.
– Thus, the processing can be divided into
subtasks called modules.
– Each module accomplishes one function.
– These modules are connected to each other
to show the interaction of processing between
the modules.
PRE-PROGRAMMING PHASE
• Main/control module controls the flow all
other modules.
• The IC is developed using top-downmethod: top to down left to right order
(also refer to order of processing).
• Modules are numbered, marked for
duplication, repetition or decision.
PRE-PROGRAMMING PHASE
• The interaction will form a hierarchy, called Hierarchy Input Process
Output Chart (HIPO) or Interactivity Chart (IC). Programming which
use this approach (problem is divided into subtasks) is called
Structured Programming.
Main Module
Module 1
Module 4
Module 2
Module 3
Module 5
Module 6
PRE-PROGRAMMING PHASE
PAYROLL
0000
READ
1000
CALCULATE
2000
PRINT
3000
PRE-PROGRAMMING PHASE
Example 2.2: Extended Payroll Problem
You are required to write a program to calculate both the
gross pay and the net pay of every employee of your
company. To determine the gross pay, you have to
multiply the accumulated total hours worked by the
employee, by the appropriate pay rate. The program
should print the cheque that tells the total net pay. The
net pay is calculated by subtracting the gross pay with
any deductions that may be incurred by the employee.
PRE-PROGRAMMING PHASE
Payroll
0000
Calculate
Gross Pay
1000
Accumulate
Hourly
Worked
1100
Determine
Pay rate
1200
Calculate
Net Pay
2000
Calculate
Deductions
2100
Write
Cheque
3000
Problem 2
• Write a Hierarchy Input Process Output (HIPO) to find an
area of a circle where area = pi * radius * radius
Area
0000
radius
1000
area = 3.14 x
radius x radius
2000
Display area
3000
Problem 3
• Write a Hierarchy Input Process Output (HIPO) to compute and
display the temperature inside the earth in Celsius and Fahrenheit.
The relevant formulas are
Celsius = 10 x (depth) + 20
Fahrenheit = 1.8 x (Celsius) + 32
Temperature
0000
Calculate temperature
in celsius
1000
Get depth
1100
Calculate temperature
In fahrenheit
2000
Display
Temperature
3000
Problem 4
• Write a Hierarchy Input Process Output
(HIPO) that asks a user to enter the
distance of a trip in miles, the miles per
gallon estimate for the user’s car, and the
average cost of a gallon of gas. Calculate
and display the number of gallons of gas
needed and the estimated cost of the trip.
Estimation Cost
0000
Calculate gas
Needed
1000
Get total distance
in miles
1100
Calculate estimated
Cost
2000
Get miles
per gallon
1200
Get average cost
per gallon
2100
Display gas needed
Display estimated
Cost
3000
Extra Problem
Extended Extra Problem
Find the total sale if the customer is given
20% discount on the sale items
PRE-PROGRAMMING PHASE
• Developing the Input Process Output
(IPO) Chart
– Extends and organizes the information in the
Problem Analysis Chart.
– It shows in more detail what data items are
input, what are the processing or modules on
that data, and what will be the result or output.
– It combines information from PAC and HIPO
Chart.
PRE-PROGRAMMING PHASE
IPO Chart
Input
All input
data from
PAC
Processing
Module
All processing steps Module
from HIPO / IC
reference
from the IC
Output
All output
requirements
from PAC
PRE-PROGRAMMING PHASE
IPO for Extended Payroll Problem
Input
-Hours Worked
-Pay Rate
-Deduction
Processing
-Enter Hourly Worked
-Enter Pay Rate
-Calculate Gross Pay
-Enter Deductions
-Calculate Net Pay
-Print Cheque
-End
Module Output
1100
1200
1000
2100
2000
3000
0000
-Net pay
Problem 2
• Write a Input Process Output (IPO) to find an
area of a circle where area = pi * radius * radius
Input
- radius
Processing
- Enter radius
- area = 3.14 x radius x radius
-Display area
-end
Module
1000
2000
3000
0000
Output
- Area of a circle
Problem 3
• Write an Input Process Output (IPO) to compute and display the
temperature inside the earth in Celsius and Fahrenheit. The relevant
formulas are
Celsius = 10 x (depth) + 20
Fahrenheit = 1.8 x (Celsius) + 32
Problem 4
• Write an Input Process Output (IPO) that
asks a user to enter the distance of a trip
in miles, the miles per gallon estimate for
the user’s car, and the average cost of a
gallon of gas. Calculate and display the
number of gallons of gas needed and the
estimated cost of the trip.
Input
- Distance in
miles
- Miles per
gallon
- Cost gas per
gallon
Processing
- Enter distance
- Enter miles per gallon
- Calculate total gas
needed
- Enter cost gas per
gallon
- Calculate estimated cost
- Display total gas and
estimated cost
- End
Module
1100
1200
1000
2100
2000
3000
0000
Output
-Total gas
needed
- Estimated
cost
Extra Problem
Extended Extra Problem
Write a IPO chart that asks a user to enter
a unit price and quantity of the product
sold . Calculate and display the total sale
Find the total sale if the customer is given
20% discount on the sale items.
PRE-PROGRAMMING PHASE
• Drawing the Program Flowcharts
– Flowchart is the graphic representations of the
individual steps or actions to implement a particular
module.
– The flowchart can be likened to the blueprint of a
building. An architect draws a blueprint before
beginning construction on a building, so the
programmer draws a flowchart before writing a
program.
– Flowchart is independent of any programming
language.
PRE-PROGRAMMING PHASE
– Flowchart is the logical design of a program.
– It is the basis from which the actual program
code is developed.
– Flowchart serves as documentation for computer
program.
– The flowchart must be drawn according to definite
rules and utilizes standard symbols adopted
internationally.
– The International Organization for Standardization
(IOS) was the symbols shown below (You can draw
the symbols using ready-made flowcharting
template):
PRE-PROGRAMMING PHASE
Symbol
Function
Show the direction of data flow or logical
solution.
Indicate the beginning and ending of a set of
actions or instructions (logical flow) of a module
or program.
Indicate a process, such as calculations,
opening and closing files.
PRE-PROGRAMMING PHASE
Indicate input to the program and output from the
program.
Use for making decision. Either True or False based
on certain condition.
Use for doing a repetition or looping of certain steps.
Connection of flowchart on the same page.
Connection of flowchart from page to page.
PRE-PROGRAMMING PHASE
• Example 2.3 : Sale Problem
– Draw a flowchart for a problem that to read two
numbers. The first number represents the unit price of
a product and the second number represents the
quantity of the product sold. Calculate and print the
total sale.
– Solution: Stepwise Analysis of the Sale Problem
•
•
•
•
•
•
Start of processing
Read the unit price
Read the quantity
Calculate total sale
Print total sale
Stop the processing
PRE-PROGRAMMING PHASE
START
READ
UNIT PRICE
A
TOTAL SALE =
UNITPRICE  QUANTITY
READ
QUANTITY
PRINT
TOTALSALE
A
STOP
PRE-PROGRAMMING PHASE
• Finding Average Problem
– Read a sequence of number, find the average of the
number and print the average.
– Solution: Stepwise Analysis of Average Problem
•
•
•
•
•
•
•
Start the processing
Read a number
Add the number
Repeat reading until last data
Calculate the average
Print the average
Stop the processing
PRE-PROGRAMMING PHASE
START
READ
NUMBER
ACCUMULATE
TOTAL
CALCULATE
AVERAGE
PRINT
AVERAGE
STOP
Repetition until end of data
PRE-PROGRAMMING PHASE
START
COUNTER
=
X
AVERAGE = TOTAL
READ NUMBER
COUNTER
PRINT AVERAGE
TOTAL = TOTAL + NUMBER
COUNTER = COUNTER + 1
STOP
END OF
DATA
X
B
START
AVERAGE = TOTAL
COUNTER
COUNTER
=
PRINT
AVERAGE
TOTAL
=
A
STOP
READ
NUMBER
NUMBER =
-999999
COUNTER = COUNTER + 1
TOTAL = TOTAL + NUMBER
A
B
PRE-PROGRAMMING PHASE
• Writing the Algorithm (Pseudocode)
– Pseudocode means an imitation computer code.
– It is used in place of symbols or a flowchart to
describe the logic of a program. Thus, it is a set of
instructions (descriptive form) to describe the logic of
a program.
– Pseudocode is close to the actual programming
language.
– Using the Pseudocode, the programmer can start to
write the actual code.
START
READ
PRICE
Algorithm:
Start
READ
QUANTITY
SALE = PRICE 
QUANTITY
PRINT
SALE
STOP
Read price, quantity
Sale = price x quantity
Print Sale
End
Example: Flowchart & Algorithm
Order of Execution of Instructions : Payroll System
Structuring a Program
•
Develop efficient computer solution to problems:
1.
2.
Use Modules
Use four logic structures
a. Sequential structure
• Executes instructions one after another in a sequence.
b. Decision structure
• Branches to execute one of two possible sets of
instructions.
c. Loop structure
• Executes set of instruction many times.
d. Case structure
• Executes one set of instructions out of several sets.
3. Eliminate rewriting of identical process by using modules.
4. Use techniques to improve readability including four logic
structure, proper naming of variables, internal documentation
and proper indentation.
Sequential Logic Structure
The Decision Logic Structure
• Implements using the IF/THEN/ELSE instruction.
• Tells the computer that IF a condition is true,
THEN execute a set of instructions, or ELSE
execute another set of instructions
• ELSE part is optional, as there is not always a set
of instructions if the conditions are false.
• Algorithm:
IF <condition(s)> THEN
<TRUE instruction(s)>
ELSE
<FALSE instruction(s)
Decision Logic Structure
Examples of conditional expressions
• A < B (A and B are the same data type
– either numeric, character, or string)
• X + 5 >= Z (X and Z are numeric data)
• E < 5 or F > 10 (E and F are numeric
data)
• DATAOK (DATAOK – logical datum)
Example
• Assume your are calculating pay at an
hourly rate, and overtime pay(over 40
hours) at 1.5 times the hourly rate.
– IF the hours are greater than 40, THEN the
pay is calculated for overtime, or ELSE the
pay is calculated in the usual way.
Example Decision Structure
NESTED IF/THEN/ELSE
INSTRUCTIONS
• Multiple decisions.
• Instructions are sets of instruction in which
each level of a decision is embedded in a
level before it.
NESTED IF/THEN/ELSE INSTRUCTIONS
EXERCISE
A hotel has a pricing policy as follows:
- 2 people : RM85
- 3 people : RM90
- 4 people : RM95
- Additional people : RM6 per person
If the customer is staying on company business,
there is a 20% discount. If the customer is over 60
years of age, there is a 15% discount. A customer
does not receive both discount. Given the above
data, print the cost of the room
The Loop Logic Structure
• Repeat structure
• To solve the problem that doing the same
task over and over for different sets of data
• Types of loop:
– WHILE loop
– Do..WHILE loop
– Automatic-Counter Loop
Loop Logic Structure
WHILE loop
WHILE loop
• Do the loop body if the condition is true.
• Example: Get the sum of 1, 2, 3, …, 100.
– Algorithm:
• Set the number = 1
• Set the total = 0
• While (number <= 100)
– total = total + number
– number = number + 1
• End While
• Display total
WHILE loop
Start
Set number = 1
Set total = 0
number <= 100
Yes
total =
total + number
number =
number + 1
No
Display total
End
DO…WHILE Loop
• The body of the loop will process first
before check the condition.
• Example: Get the sum of 1, 2, 3, …100.
Algorithm:
Set the number = 1
Set the total = 0
Do
total = total + number
number = number + 1
While (number <= 100)
Display total
DO…WHILE Loop
Start
Set number = 1
Set total = 0
total =
total + number
number =
number + 1
Yes
No
Display total
End
number <= 100
Automatic Counter Loop
• Use variable as a counter that starts
counting at a specified number and
increments the variable each time the loop is
processed.
• The beginning value, the ending value and
the increment value may be constant. They
should not be changed during the
processing of the instruction in the loop.
Automatic-Counter Loop
Automatic-Counter Loop
NESTED LOOP
NESTED LOOP
EXAMPLE OF NESTED LOOP
An algorithm to find total marks of test1, test2
and final and also average of the marks for each
student in class SAK3100 Group 2.
LOOP: J = 1 TO 35
SET JUMLAH = 0
LOOP: K= 1 TO 3
SET TEST = 0
PRINT “MASUKKAN MARKAH TEST”, K
READ TEST
JUMLAH = JUMLAH + TEST
LOOP-END: K
PURATA = JUMLAH / 3
PRINT “MARKAH PELAJAR KE “, J, “ = “, JUMLAH, “PURATA MARKAH = “,
PURATA
LOOP-END: J
PRINT “ITU JUMLAH DAN PURATA MARKAH SEMUA PELAJAR DALAM KELAS SAK3100 K2”
END
The Case Logic Structure
• Made up of several or many sets of instructions,
only one of which will be selected by the user and
executed by the computer
• Algorithm:
CASE OF VARIABLE
= constant1:
actions for VARIABLE = constant1
= constants2:
actions for VARIABLE = constant2
…
OTHERWISE:
Actions for VARIABLE = anything else
END-OF-CASE
Case Logic Structure
Case Logic Structure
• Example: A company has four different medical
plans. The programmer has given each plan a code
corresponding to the beginning initial of the
company: Plan 1 = F, Plan 2 = B, Plan 3 = K, Plan 4
= E.
The company pays for all of Plan 1. The individual
has to pay for part of the others. The payroll
deduction for Plan 2 = 4.65, for Plan 3 = 7.85, and
for Plan 4 = 5.50. Any other codes are considered in
error. Write the algorithm and draw the flowchart for
a module to determine the payroll deduction.
Example of Case Logic Structure
Case Logic Structure
A module calculate an employee’s pay as shown
below. It has pay-type code and the pay rate to
calculate the employee’s pay.
H = hourly
P = Piece work
C = commission
S = salary
pay = rate * hours
pay = rate * number of pieces
pay = commission * sales
pay = salary
Exercises
Programming Or Implementation
Phase
• Transcribing the logical flow of solution steps in
flowchart or algorithm to program code and run
the program code on a computer using a
programming language.
• Programming phase takes 5 stages:
•
•
•
•
•
Coding.
Compiling.
Debugging.
Run or Testing.
Documentation and maintenance.
Programming Or Implementation
Phase
• Once the program is coded using one of the
programming language, it will be compiled to
ensure there is no syntax error. Syntax free
program will then be executed to produce
output and subsequently maintained and
documented for later reference.
CODING
COMPILE THE
PROGRAM
NO SYNTAX
ERROR
EXECUTE OR
RUN
DOCUMENTATION
OR MAINTENANCE
MAKE
CORRECTION
Programming Or Implementation
Phase
• Coding
– Translation or conversion of each operation in the
flowchart or algorithm (pseudocode) into a computerunderstandable language.
– Coding should follow the format of the chosen
programming language.
– Many types or levels of computer programming
language such as:
– Machine language
– Symbolic language or assembly language
– Procedure-oriented language
– The first two languages are also called low-level
programming language. While the last one is called
high-level programming language.
Programming Or Implementation
Phase
• Machine Language
– Machine language uses number to represent letters,
alphabets or special character that are used to
represent bit pattern.
– Example:
• an instruction to add regular pay to overtime pay, yielding
total pay might be written in machine language as follows:
16 128 64 8
• in which 16 is a code that mean ADD to the computer. The
128 and 64 are addresses or location at which regular pay
and overtime pay are stored. The 8 represents the storage
location for the total pay.
Programming Or Implementation
Phase
• Sometimes, bit pattern that represent
letters and alphabets are used for coding.
– Example:
Instead of:
Use:
16
128
64
8
10000 10000000 1000000 1000
– This representation is ideal for a computer but
difficult and tedious to the programmer to
write a lengthy program.
Programming Or Implementation
Phase
• Symbolic Language or Assembly Language
– A symbolic language or assembly language is closely related to
machine language in that, one symbolic instruction will translate
into one machine-language instruction.
– Contain fewer symbols, and these symbols may be letters and
special characters, as well as numbers.
– As example, a machine language instruction
16 128 64 8
can be rewritten in assembly language as
ADD LOC1 LOC2 LOC3
– Which means, add content of location LOC1 to location LOC2
and put the result in location LOC3.
Programming Or Implementation
Phase
• Procedure – Oriented Language
– Programmer has to know the computer hardware
before he can write program in machine and
assembly language. It means the language is
machine dependent.
– Using procedure – oriented language, the
programmer can run the program in any computer
hardware.
– A special program called a compiler will translate
program written using procedure – oriented language
to machine language.
Programming Or Implementation
Phase
• Some example of the language:
–
–
–
–
–
–
COBOL (COmmon Business Oriented Language)
FORTRAN (FORmula TRANslation)
Pascal
C
C++
BASIC, etc.
• These languages are also called high-level
programming language
Programming Or Implementation
Phase
Computer
Language
Instruction Format
Machine language
Assembly language
BASIC
FORTRAN
COBOL
Pascal
C
16 128 64 8
ADD LOC1 LOC2 LOC3
LET T = R + 0
TOTAL = RPAY + OPAY
ADD RPAY, OPAY GIVING TOTAL
TOTAL : = RPAY + OPAY
TOTAL = RPAY + OPAY
Programming Or Implementation
Phase
• Compiling and Debugging
– Compiling is a process of a compiler translates a
program written in a particular high–level
programming language into a form that the computer
can execute.
– The compiler will check the program code known also
as source code so that any part of the source code
that does not follow the format or any other language
requirements will be flagged as syntax error.
– This syntax error in also called bug, when error is
found, the programmer will debug or correct the error
and then recompile the source code again.
– The debugging process is continued until there is no
more error in the program.
Programming Or Implementation
Phase
• Testing
– The program code that contains no more error is
called executable program. It is ready to be tested.
– When it is tested, the data is given and the result is
verified so that it should produced output as intended.
– Though the program is error free, sometimes it does
not produced the right result. In this case the program
faces logic error.
– Incorrect sequence of instruction is an example that
causes logic error.
Programming Or Implementation
Phase
• Documentation and Maintenance
– When the program is thoroughly tested for a substantial period of
time and it is consistently producing the right output, it can be
documented.
– Documentation is important for future reference. Other
programmer may take over the operation of the program and the
best way to understand a program is by studying the
documentation.
– Trying to understand the logic of the program by looking at the
source code is not a good approach.
– Studying the documentation is necessary when the program is
subjected to enhancement or modification.
– Documentation is also necessary for management use as well
as audit purposes.
Cohesion and Coupling
• Especially important concepts to the modern
programmer, who in all probability will be working
with many other programmers on the same
problem.
• Cohesion allows a programmer to write a module
of a large program and test it independently.
• Coupling allows all programmers to use necessary
variables without losing the cohesion.
Cohesion
• Cohesion relates to the functional
independence of the module and to the
performance of a single task within the
module.
• The objective is to separate the problem into
parts.
• Each module is independent of each other
module, with single entrance and a single
exit, such as entering data, printing data,
initialising data.
Coupling
• Coupling allows modules to be connected by an
interface, which enables the programmer to
transfer data from one module to another.
• Three coupling techniques are:
– Parameter
– Modules names
– Global variables.
• Allows for communication between modules.
• Coupling allows all programmers to use necessary
variable without losing the cohesion of the
module.
Cohesion and Coupling
Cohesion is the ability for each module to be
independent of other modules.
Module 2
Module 1
Coupling
allows
modules to
share data
Module 3
Module 4
The Modules and The Functions
• The programmer breaks the problem into
modules, each with specific function.
• It is much easier to write and test many
small modules than a single large program.
• Modules are arranged according to
processing order in interactivity chart.
The rules for designing modules
1. Each module is an entity and has one entrance
and one exit.
2. Each module has a single function such as
printing, calculating or entering data.
3. Each module is short enough to be easily read
and modified.
4. The length of module governed by its function
and the number of instruction to be executed.
5. A module is developed to control the order of
processing.
Types of modules
1. Control module
• Show the overall flow of data through the program.
All other modules are subordinate to it.
2. Init module
• Also called the preparation module, process
instruction that are executed only once – at the
beginning.
3. Process Data module
• May be processed only once, or may be part of a
loop.
1. Calculation Modules
• Do arithmetic calculations.
Types of modules
2. Print Modules
• Print output lines.
3. Read and Data validation modules
• Read or input data, validate data
• Validation modules separate from read modules
4.
Wrap-up module
• Execute only once at the end.
• Include closing file and printing totals.
5. Event module
• Such as mouse down, mouse up, key entry.
Local and Global Variables
• The concept of local and global variables to
allow cohesion and coupling to occur.
• Local variables
– defined within a module
– used only by the module itself
• Global variables
– defined outside of the individual modules
– can be used by all modules
Scope of Local and Global Variables
Variables: A, B, C
CONTROL MODULE
Variables: X, Y, Z
MODULE1
Variables: D, E, F
MODULE2
Variables: G, H, I
Global to all modules
Local to CONTROL
MODULE
Local to MODULE1
Local to MODULE2
Parameters
• Parameters are local variables that are passed or sent
from one module to another.
• Parameters are another way of facilitating coupling that
allows the communication of data between modules.
• Eg: Read(A, B, C) – A, B & C are parameters
• There are two types of parameters:
– Actual Parameter
list of parameters that follow the module name being processed in
the calling module
– Formal Parameter
list of parameters that follow the module name at the beginning of
the module.
Parameter Terminology
Beginning Problem-Solving Concepts
for the Computer
• Data used in processing
• Constant is a value that never changes
during the processing of all instructions in a
solution
• Constant is given a location in memory and a
name.
• The value of a variable may change during
processing
Rules for naming and using
variables:
•
•
•
•
•
Name according to what it represented
Do not use spaces in a variable name
Do not a dash
Consistent in the use of variable names
Consistent when using upper and
lowercase characters
Data Types
• Data are unorganized facts
• Goes as input and is processed to produce
output, information
• Computers must be told the data type of each
variable and constant
• 3 common types: numeric, character, and
logical
• Other data types: date data type and userdefined data types
Rules of Data Types
• Programmer designates the data type
during the programming process
• Data types cannot be mixed
• Each data types used data set
• Calculations involved only numeric data
type.
Functions
• Small sets of instructions that perform specific task and return values
• Used as part of instruction in a solution
• Divided into classes:
– Mathematical functions – used in science and business
– String functions – used to manipulate string variables
– Conversion functions – used to convert data from one data type to
another
– Statistical functions – used to calculate things such as maximum
value
– Utility functions – access information outside the program, i.e. date
and time function
• Functions use data, called parameters. Functions normally do not alter
parameters
Functionname(parameters list)
Operators
• They are data connectors within expressions and
equations.
• They tell computer how to process the data
• Operands are data the operator connects and
processes
• Resultant is the answer
• Data type of the operand and the resultant depends
on the operator:
– Mathematical operators
– Relational operators
– Logical operators
• Operators have a hierarchy or precedence
Expressions and Equations
• Expression processes data, the operands,
through the use of operators
• Equation stores the resultant of an
expression in a memory location in the
computer through the equal (=) sign.
• Equations are often called assignment
statements

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