1. CHAPTER 2 PROBLEM SOLVING

2. This chapter will cover the following topics:
Problem Solving Concepts for the Computer
Pre-Programming Phase
Programming Or Implementation Phase

3. 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.

4. PRE-PROGRAMMING PHASE
This phase requires five steps:
Analyzing the problem - PAC
Developing the Hierarchy Input Process Output (HIPO) chart or Interactivity Chart (IC).
Developing the Input-Process-Output (IPO) Chart.
Drawing the Program flowcharts.
Writing the algorithms.

5. PRE-PROGRAMMING PHASE
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.

6. PRE-PROGRAMMING PHASE
All These requirements can be presented in a Problem Analysis Chart (PAC)
Data
Processing
Output
given in the problem or provided by the user
List of processing required or procedures.
Output requirement.

7. 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,
Pay rate
Salary = Hours work * payrate
Salary

8. Problem 1 Write a Problem Analysis Chart (PAC) to convert
the distance in miles to kilometers where 1.609
kilometers per mile.
Data
Processing
Output
Distance in miles
Kilometers = x miles
Distance in kilometers

9. Problem 2
Write a Problem Analysis Chart (PAC) to find an area of a circle where area = pi * radius * radius
Data
Processing
Output
radius
area = 3.14 x radius x radius
area

10. Problem 3 Data Processing Output depth celsius = 10 x (depth) + 20
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
fahrenheit = 1.8 x (celsius) + 32
Display celsius,
Display fahrenheit

11. 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.

12. Data Processing Output distance, miles per gallon, cost per gallon
gas needed = distance / miles per gallon.
estimated cost = cost per gallon x gas needed
Display gas needed
Display estimated cost

13. 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

14. 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.

15. PRE-PROGRAMMING PHASE
Main/control module controls the flow all other modules.
The IC is developed using top-down-method: top to down left to right order (also refer to order of processing).
Modules are numbered, marked for duplication, repetition or decision.

16. 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 3
Module 2
Module 1
Module 5
Module 4
Module 6

17. PRE-PROGRAMMING PHASE
PAYROLL
0000
READ
1000
PRINT
3000
CALCULATE
2000

18. 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.

19. PRE-PROGRAMMING PHASE
Accumulate
Hourly
Worked
1100
Payroll
0000
Calculate
Gross Pay
1000
Determine
Pay rate
1200
Write
Cheque
3000
Net Pay
2000
Deductions
2100

20. Problem 1 Write a Hierarchy Input Process Output (HIPO) to convert
the distance in miles to kilometers where 1.609
kilometers per mile.

21. Problem 2
Write a Hierarchy Input Process Output (HIPO) to find an area of a circle where area = pi * radius * radius

22. 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

23. 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.

25. Extra Problem Extended Extra Problem
Find the total sale if the customer is given 20% discount on the sale items

26. 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.

27. PRE-PROGRAMMING PHASE
IPO Chart
Input
Processing
Module
Output
All input data from PAC
All processing steps from HIPO / IC
Module reference from the IC
All output requirements from PAC

28. PRE-PROGRAMMING PHASE
IPO for Extended Payroll Problem
Input
Processing
Module
Output
-Hours Worked -Pay Rate
-Deduction
-Enter Hourly Worked
-Enter Pay Rate
-Calculate Gross Pay
-Enter Deductions
-Calculate Net Pay
-Print Cheque
-End
1100
1200
1000
2100
2000
3000
0000
-Net pay

29. Problem 1 Write a Input Process Output (IPO) to convert
the distance in miles to kilometers where 1.609
kilometers per mile.
Input
Processing
Module
Output
-Distance in Miles
-Enter distance
-Kilometers = x distance
-Display kilometers
1000
2000
3000
-Distance in kilometers

30. Problem 2
Write a Input Process Output (IPO) to find an area of a circle where area = pi * radius * radius
Input
Processing
Module
Output
- radius
- Enter radius
- area = 3.14 x radius x radius
Display area
end
1000
2000
3000
0000
- Area of a circle

31. 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

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.

33. Input
Processing
Module
Output
Distance in miles
Miles per gallon
Cost gas per gallon
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
1100
1200
1000
2100
2000
3000
0000
Total gas needed
Estimated cost

34. 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.

35. 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.

36. 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):

37. 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.

38. 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.

39. 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

40. PRE-PROGRAMMING PHASE
START
READ
UNIT PRICE
QUANTITY A
TOTAL SALE =
UNITPRICE ´ QUANTITY
PRINT
TOTALSALE
STOP

41. 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

42. PRE-PROGRAMMING PHASE
START
READ
NUMBER
ACCUMULATE
TOTAL
CALCULATE
AVERAGE
PRINT
STOP
Repetition until end of data

43. PRE-PROGRAMMING PHASE
START X
COUNTER
= Æ
AVERAGE = TOTAL
COUNTER
READ NUMBER
PRINT AVERAGE
TOTAL = TOTAL + NUMBER
COUNTER = COUNTER + 1
STOP
END OF DATA X

44. COUNTER = COUNTER + 1 B START AVERAGE = TOTAL COUNTER COUNTER = Æ
PRINT
AVERAGE
TOTAL
= Æ A
STOP
READ
NUMBER
NUMBER = B
COUNTER = COUNTER + 1
TOTAL = TOTAL + NUMBER A

45. 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.

46. START READ PRICE QUANTITY SALE = PRICE ´ PRINT SALE STOP Algorithm:
Sale = price x quantity
Print Sale End

47. Example: Flowchart & Algorithm

48. Order of Execution of Instructions : Payroll System

49. Structuring a Program Develop efficient computer solution to problems:
Use Modules
Use four logic structures
Sequential structure
Executes instructions one after another in a sequence.
Decision structure
Branches to execute one of two possible sets of instructions.
Loop structure
Executes set of instruction many times.
Case structure
Executes one set of instructions out of several sets.
Eliminate rewriting of identical process by using modules.
Use techniques to improve readability including four logic structure, proper naming of variables, internal documentation and proper indentation.

50. Sequential Logic Structure

51. 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)

52. Decision Logic Structure

53. 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)

54. 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.

55. Example Decision Structure

56. 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.

57. NESTED IF/THEN/ELSE INSTRUCTIONS

58. EXERCISE A hotel has a pricing policy as follows: 2 people : RM85
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

59. 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

60. Loop Logic Structure

61. WHILE loop

62. 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

63. WHILE loop Start Set number = 1 Set total = 0 No number <= 100 Yes
total + number
number =
number + 1
Display total
End No
Yes

64. 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

65. DO…WHILE Loop Start Set number = 1 Set total = 0 total = No
total + number
number =
number + 1
Display total
End No
Yes

66. 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.

67. Automatic-Counter Loop

68. Automatic-Counter Loop

69. NESTED LOOP

70. NESTED LOOP

71. 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

72. 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

73. Case Logic Structure

74. 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 = Any other codes are considered in error. Write the algorithm and draw the flowchart for a module to determine the payroll deduction.

75. Example of Case Logic Structure

76. 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 pay = rate * hours
P = Piece work pay = rate * number of pieces
C = commission pay = commission * sales
S = salary pay = salary

77. Exercises

78. 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.

79. 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.

80. DOCUMENTATION OR MAINTENANCE
CODING
COMPILE THE
PROGRAM
MAKE
CORRECTION
NO SYNTAX
ERROR
EXECUTE OR
RUN
DOCUMENTATION OR MAINTENANCE

81. Programming Or Implementation Phase
Coding
Translation or conversion of each operation in the flowchart or algorithm (pseudocode) into a computer-understandable 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.

82. 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:
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.

83. Programming Or Implementation Phase
Sometimes, bit pattern that represent letters and alphabets are used for coding.
Example:
Instead of:
Use:
This representation is ideal for a computer but difficult and tedious to the programmer to write a lengthy program.

84. 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
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.

85. 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.

86. 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

87. Programming Or Implementation Phase
Computer Language
Instruction Format
Machine language
Assembly language
BASIC
FORTRAN
COBOL
Pascal C
ADD LOC1 LOC2 LOC3
LET T = R + 0
TOTAL = RPAY + OPAY
ADD RPAY, OPAY GIVING TOTAL
TOTAL : = RPAY + OPAY

88. 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.

89. 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.

90. 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.

91. 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.

92. 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.

93. 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.

94. Cohesion and Coupling Module 1 Module 2 Module 3 Module 4
Cohesion is the ability for each module to be
independent of other modules.
Coupling allows modules to share data

95. 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.

96. The rules for designing modules
Each module is an entity and has one entrance and one exit.
Each module has a single function such as printing, calculating or entering data.
Each module is short enough to be easily read and modified.
The length of module governed by its function and the number of instruction to be executed.
A module is developed to control the order of processing.

97. Types of modules Control module
Show the overall flow of data through the program. All other modules are subordinate to it.
Init module
Also called the preparation module, process instruction that are executed only once – at the beginning.
Process Data module
May be processed only once, or may be part of a loop.
Calculation Modules
Do arithmetic calculations.

98. Types of modules Wrap-up module Execute only once at the end.
Print Modules
Print output lines.
Read and Data validation modules
Read or input data, validate data
Validation modules separate from read modules
Wrap-up module
Execute only once at the end.
Include closing file and printing totals.
Event module
Such as mouse down, mouse up, key entry.

99. 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

100. 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

101. 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.

102. Parameter Terminology

103. 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

104. 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

105. 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 user- defined data types

107. 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.

108. 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)

109. 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

111. 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