PROGRAM LOGIC AND FORMULATION

GENERATIONS OF COMPUTER
 ABACUS - Developed around 300 years
BC by the Mesopotamians and later
improved by Chinese.
 An abacus consists of beads divided into
two parts which are movable on the rods of
the two parts.


FIRST GENERATION COMPUTER (1940 - 1956)
Vacuum Tubes
 ENIAC (Electronic numerical Integrated And
Computer).
 Developed by Presper Eckert and John Mauchly ,
ENIAC was made up of 18,000 vacuum tubes and
occupied a 30 x 50 feet room.
 Programming was done by plugging wires into a
patch panel.
KEY FEATURES :
Big and Clumsy Computers
that used Vacuum Tubes.
Not very reliable as Electric
failure occurred regularly.
Large air Conditioners were
necessary because the
computers Generated lot of
heat.
Used stored program
concept.
Input and Output Devices :
Either No Input Devices
REMARKS :
Very large space requirement.
High electricity consumption.
Generated lot of heat.
Slow operating speed.
Restricted computing
capacity.
Limited Programming
capabilities.
Memory Type : Magnetic Drums
Storage: Punched Cards and

FIRST GENERATION COMPUTER (1940 - 1956)
Vacuum Tubes
 Trajectory tables for weapons. (too late for war
effort).
 Programmed manually by Switches.
 18,000 vacuum tubes.
 30 tons
 15,000 square feet
 140 kW power consumption
 5,000 additions per second.
DISADVANTAGES:
1. They were to bulky.
2. They emitted large amounts of heat because they
used lots of vacuum tubes.
3. AIR conditioning was required.
4. They were Prone to frequent that’s why they were
unreliable.

SECOND GENERATION COMPUTER(1956 - 1963)
Transistors
 The creation of transistor sparked the production of
a wave of second generation computer. Transistor
was a small device used to transfer the electronic
signals across a resistor. Transistors had many
advantages compared to vacuum tubes.KEY FEATURES :
Transistors replaced vacuum
tubes.
Smaller in size compared to
1st generation computers.
Generated lesser heat than
earlier computer.
Low electricity consumption.
More reliable and faster.
Input Devices and Output
Devices : Punched Cards.
REMARKS :
Not General – purpose
computers – mostly suitable to
scientific and bulk data
processing tasks only; not for
business purposes.
The machines were costly
Frequent Maintenance
required. .

THIRD GENERATION COMPUTER(1964 - 1971)
Integrated Circuits
 The development of integrated circuits (IC) in 1961,
signaled the beginning of the third generation
computers and the integrated circuit technology,
which had reduced the size and cost of computers
enormously.
 It is also known as Semiconductor.
KEY FEATURES :
Integrated Circuits
Computers Smaller , faster
and more reliable.
Lower power consumption
High level languages
developed
Input and Devices : Keyboards
and printers.
REMARKS :
Proved to be highly reliable ,
relatively , inexpensive, and
faster.
Less human labour was
required at assembly stage.

FOURTH GENERATION COMPUTER(1971 - Present)
Microprocessors
 In 1971 Intel Created the first microprocessor and
the era of fourth generation computers started.
 During the fourth generation, hardware technology
such as silicone chips, microprocessors, and
storage devices were invented.
 Microprocessor is developed for computer memory
and logic.
KEY FEATURES :
Portable Computers
developed.
Great Development in data
communication.
Input and Devices : Keyboard,
mouse, joysticks , speakers etc.
REMARKS :
Computers costs came down
so rapidly that these found
places at most offices and
homes.
Smaller and faster
More speed , Reliability and
Storage Capacity.
Personal software Industry
Boomed.
Memory : Memory Chips

SOFTWARE
LESSON 2 All computer programs or routines that
control the function of hardware and affect
data are referred to as SOFTWARE.
 Software is a set of electronic instructions
consisting of complex codes (also known as
programs) that make the computer perform
tasks.
 Software tells the computer what to do.
 There are two major categories of computer
software :
System software & Application Software.

Systems software
 System software exists primarily for the
computer’s use and helps the computer
perform and manage its own task.
 One major type of the systems software, the
operating system, (tells the computer how
to use its own components.)
 Examples of operating systems include
Windows 98, Windows XP , Mac OS, Linux,
UNIX, OS/2 and DOS.

Applications
software On the other hand are types of programs
that exist primarily for the use and enable
the computer to perform tasks.
 Application software tells the computer how
to accomplish specific tasks, such as world
processing or drawing, for the user.
 Examples of popular application programs
are Microsoft Word, Adobe Photoshop,
AutoCAD, and Netscape Navigator.

PEOPLE
 People are the computer operators,
also known as users.
 Some computer systems are complete
without a person’s involvement;
however
 No computer is totally autonomous.
Even if a computer can do its job
without a person sitting in front of it,
people still building , program , and
repair computer systems.

data
 Data are raw facts that a computer stores and
reads in the form of numbers.
 The computer manipulates data according to the
instructions contained in the software and then
forwards it for use by people or another computer.
 Data can be letters, numbers, sounds, or images.
 No matter what kind of data is entered into a
computer, however, the computer converts it to
numbers. Because of this , computerized data is
digital, meaning that it has been reduced or
represented by digits, or numbers.

How computers represent
data Computers represent data as numbers. Numbers
, letters, punctuation marks, sounds and
pictures are numbers. Even instructions
performed by the computer are numbers.
 People use base 10 to represent numbers. The
system is called base 10 or the decimal number
system because ten symbols are available: 0, 1 ,2
,3, 4, 5, 6, 7, 8, 9.
 When you need to represent number greater than
9, you use two symbols together , as in (e.g. 9 + 1
= 10.) Each symbol in a number is called a digit, so
10 is a two-digit number.

data A computer, however, can only represent data by
the state of its electrical switches. A switch can only
have two possible states – on and off – so it can
represent only two numeric values. To a computer,
when a switch is off, it represents a 0; when a
switch is on, it represents a 1. because there are
only two values, computers are said to function in
base 2, which is also known as the binary number
system.
 When a computer needs to represent a quantity
greater than 1m it does the same thing to represent
a quantity greater than 9: it uses two or more digits.

data Base 10 Base 2
0 0
1 1
2 10
3 11
4 100
5 101
6 110
7 111
8 1000
9 1001
10 1010

The computer program
LESSON 3 What is a computer program?
 A computer program is a set of
statements or instructions to be fed to
the computer to solve a
computer/computing problem.
 These instructions are given and set
by a programmer.

Character set
LESSON 3 Character set are set of symbols used in the
computer.
 Character set has different types which include
data character set, arithmetic operators,
conditional operators, and punctuation
characters.
 DATA CHARACTER SET
 Data character set is made up of characters
used as data. It is composed of the ff.:
 Special Characters ( @ # $ % ^ & etc.)
 Numeric Characters ( 0 to 9 )
 Alphabetic Characters ( A to Z )

Character set
LESSON 3 ARITHMETIC OPERATORS
 Arithmetic operators are operators used to
perform certain arithmetic operations. Here are
the following arithmetic operators.
Symbol Operation
+ Addition
- Subtraction
* Multiplication
/ Division
^ Exponential
Integer Division(returns only the whole
part)
MOD Modulo Division (returns the remainder)

Character set
LESSON 3 CONDITIONAL OPERATORS
 Used in conditional instructions. Here are the ff.:
Symbol Operation
= Equal to
< Less than
<= Less than equal to
> Greater than
>= Greater than equal to
<> Or >< Not equal

Character set
LESSON 3 PUNCTUATION CHARACTERS
 Are characters that have a special purpose.
Here are examples of punctuation character
and their purpose.
Symbol Use
: (colon) used after procedure labels
, (comma) used to separate enumerations
; (semi-colon) used to terminate
instruction
“ (quote) used to enclose string constrain,
i.e., “Hello World”
‘ (apostrophe) used to enclose single
character, i.e., ‘a’

Data types
LESSON 3 Information can be classified through Data Types.
Here are some of the data type and their
characteristics.
Data Type Description
Numeric Any information that is composed of numbers
Character Any information composed of singles character
enclosed with apostrophe
Date or Time Any information that indicates Data or Time
String Any information composed of any number of
characters enclosed with quotes

Constant
LESSON 3 Constant is a quantity or values which does not
change.
 Numeric Constants – any signed or unsigned
numeric value in form of:
 Integer (i.e., 1, -1, +1)
 Fraction (i.e. 1.0, -1.2, +0.12)
 Exponentiation (i.e. 2^2)
 Non-numeric or String Constants – any
combination of characters that is enclosed in pair of
quotes.
 It consists of any combination of characters. Special
characters are also included.
 The characters are enclosed in a pair of quotes.
 It can accommodate any number of characters.

Variable
LESSON 3 Variable is a name or symbol that is used as
reference for a value.
 Rules in using variable
 The first letter of the variable name should be any
letter.
 If you will use dash(-), it should be embedded. (i.e.
Student-No)
 It can accommodate any number of characters
 String variable – a variable that stores
string data type. (i.e. FirstName, Address,
StudentNo)
 Numeric Variable – a variable that stores
numeric data type (i.e. Age, Counter,
Amount)

exercises
 Given the following data types (numeric , date or
time, string, and character). Identify the following
information.
1. ‘c’
2. “my name is rain”
3. 12/20/1979
4. “1234”
5. 1234
6. July 17, 1980
7. ‘g’
8. “December 20, 1979”
9. 1.25
10.8

OPERATIONS
LESSON 4 There are different kinds of operation
that are being used in a computer
program. They are as follows :
 Move Operation
 Arithmetic Operation
 Conditional Operation

OPERATIONS
LESSON 4 MOVE OPERATION
 Move operation causes the value of
variable to change. The operator used
in this operation is “=”
 Example :
StudentName = “Gladys Ordanel”
Age = 15
Amount = 5.00

OPERATIONS
LESSON 4 ARITHMETIC OPERATION
 Arithmetic operation is the evaluation
of arithmetic expression.
 Here is an example of an Arithmetic
Expression : 1 + 2 + 3 3 * 4
^ 5 (Age * 6 ) ^ 7
 Hierarchy of Arithmetic Operation
 In Arithmetic Operation there is a
structure to be followed to know which
arithmetic operation will be resolved
first.

OPERATIONS
LESSON 4 Here is the hierarchy to be followed
in Arithmetic Operation
1. Expression inside the parenthesis
2. Exponentiation
3. Multiplication and division. (from left
to right)
4. Integer division
5. Modulo division
6. Addition and subtraction. ( from left
to right)

OPERATIONS
LESSON 4 Example: Evaluate the following
expressions
1. 2 * 2 – 6 / 3
= 4 - 2
= 2
2. 2 * 6 ^ 2 – 20 / 5
= 2 * 36 – 4
= 72 – 4
= 68
3 * (4 + 2) / 2
= 3 * 6 / 2
= 18 / 2
= 9
4. (3 - 2) * 10 MOD 3
= 1 * 10 MOD 3
= 10 MOD 3
= 1
5. 7 (3 - 2) ^ 100 MOD 2 * 8
= 7 1 ^ 100 MOD 16
= 7 1 MOD 16
= 7

OPERATIONS
LESSON 4 CONDITIONAL OPERATION
 Conditional Operation is the resolution of
logical expression that arrives on a single
value either TRUE or FALSE.
 As addition to operators, here is the logical
operator, its symbol and description.
Symbol Description
AND / OR Binary Operators (Two Operands)
NOT Unary Operator (Single Operand)

OPERATIONS
LESSON 4 HIERARCHY OF CONDITIONAL
OPERATION
 Like the Arithmetic Operation, Conditional
Operation also has a hierarchy to know
which conditional operation will be resolved
first.
 Here is the hierarchy to be followed in
Conditional Operation
1. Expression inside the parenthesis
2. NOT operator
3. AND operator
4. OR operator

OPERATIONS
LESSON 4 Here is the table on how logical
operators generate results.
Logical AND Operator
Expr1 Expr2 Result
True True True
False True False
True False False
False False False
Logical OR Operator
Expr1 Expr2 Result
True True True
False True True
True False True
False False False
Logical NOT Operator
Expression Result
NOT True False
NOT False True

OPERATIONS
LESSON 4 Example: Evaluate the following
expressions
1. T AND T OR F AND F
= T OR F
= T
2. (F OR F) AND NOT (T AND T)
= F AND F
= F
3. F AND NOT T OR T AND NOT F
= F AND F OR T AND T
= F OR T
= T

OPERATIONS
LESSON 4 COUNTER
 Counter is a data storage used for counting.
Usually the incremental value for a counter
is 1. (e.g. ctr = ctr + 1)
 ACCUMULATOR
 Like a counter, an accumulator is also data
storage for counting but its incremental
value varies and can be stored in to a
variable. (e.g. acc = acc + var)

Exercises lesson
4 Evaluate the following arithmetic expression.
1. ( 8 / 2 ) ^ 2
2. 8 / 2 ^ 2
3. 6 + 2 – 3
4. 6 / 2 * 3
5. 2 * (2 + 3)
^ 2
 Evaluate the following conditional expression.
1. NOT T AND T.
2. NOT T OR T
3. (T OR T) AND F
4. NOT (F AND T ) AND F
5. F AND F OR T AND NOT (F AND T)

PROGRAM LOGIC AND FORMULATION

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