Unit 1 computer concepts

Unit - 1
Mithun D’Souza
Assistant Professor,
Department of Computer Science,
PES Institute of Advanced Management Studies,
Shivamogga

Printer
(output)
Monitor
(output)
Speaker
(output)
Scanner
(input)
Mouse
(input)
Keyboard
(input)
System unit
(processor,
memory…)
Storage
devices
(CD-RW,
Floppy, Hard
disk, zip,…)
Devices that comprise a computer system

• IntroductionTo Computer Software
• Operating system
• Problem solvingTechniques
• Computer Prog ramming languages
• ComputerThreats

•Before the 1500s, in Europe, calculations were made
with an abacus
Invented around 500BC, available in many
cultures (China, Mesopotamia, Japan, Greece,
Rome, etc.)
•In 1642, Blaise Pascal (French mathematician,
physicist, philosopher) invented a mechanical
calculator called the Pascaline
•In 1671, Gottfried von Leibniz (German
mathematician, philosopher) extended the Pascaline to
do multiplications, divisions, square roots: the Stepped
Reckoner
None of these machines had memory, and they
required human intervention at each step

• In 1822 Charles Babbage (English
mathematician, philosopher), sometimes
called the “father of computing” built the
Difference Engine
• Machine designed to automate the
computation (tabulation) of polynomial
functions (which are known to be good
approximations of many useful functions)
– Based on the “method of finite
difference”
– Implements some storage
• In 1833 Babbage designed the Analytical
Engine, but he died before he could build it
– It was built after his death, powered by
steam

• Generation of Computers
• First Generation (1946-59)
• Second Generation(1957-64)
• Third Generation(1965-70)
• Fourth Generation(1970-90)
• Fifth Generation(1990 till date)
 Generation 0: Mechanical Calculators
 Generation 1: Vacuum Tube Computers
 Generation 2: Transistor Computers
 Generation 3: Integrated Circuits
 Generation 4: Microprocessors

First
Generation
Second
Gen.
Third
Gen.
Fourth Gen.
Technology Vacuum
Tubes
Transistors Integrated
Circuits
(multiple
transistors)
Microchips
(millions of
transistors)
Size Filled Whole
Buildings
Filled half a
room
Smaller Tiny - Palm
Pilot is as
powerful as
old building
sized
computer

Generation 1 : ENIAC
The ENIAC (Electronic Numerical Integrator and Computer) was unveiled in 1946: the
first all-electronic, general-purpose digital computer

Generation 2: IBM7094
Generations of Computers

CPU Memory
I/O
System

Generation 3: IntegratedCircuits
Seymour Cray created the Cray Research
Corporation
Cray-1: $8.8 million, 160 million instructions
per seconds and 8 Mbytes of memory

Generation 4:VLSI
Improvements to IC technology made it possible to
integrate more and more transistors in a single chip
•SSI (Small Scale Integration): 10-100
•MSI (Medium Scale Integration): 100-1,000
•LSI (Large Scale Integration): 1,000-10,000
•VLSI (Very Large Scale Integration): >10,000
Microprocessors

Generation 5?
The term “Generation 5” is used sometimes to refer to all
more or less “sci-fi” future developments
Voice recognition
Artificial intelligence
Quantum computing
Bio computing
Nano technology
Learning
Natural languages

 According to functionality, Type of computers are
 Analog Computer
 Digital Computer
 Hybrid Computer (Analog + Digital)
 On the basis of Size: Type of Computers are
 Super Computer
 Mainframe Computer
 Mini Computer
 Micro Computer or Personal Computer
 Workstations

Type Specifications
PC (Personal Computer)
It is a single user computer system having moderately
powerful microprocessor
Workstation
It is also a single user computer system, similar to personal
computer however has a more powerful microprocessor.
Mini Computer
It is a multi-user computer system, capable of supporting
hundreds of users simultaneously.
Main Frame
It is a multi-user computer system, capable of supporting
hundreds of users simultaneously. Software technology is
different from minicomputer.
Supercomputer
It is an extremely fast computer, which can execute
hundreds of millions of instructions per second.

 Designed for an Individual User (single-user systems)– Small and
relatively inexpensive computer
 Based on microprocessor technology that enables manufacturers to
put an entire CPU on one chip.
 Businesses use PCs for word processing, accounting, desktop
publishing and for running spreadsheet and database management
applications.
 At Home, the most popular use for personal computers is playing
games and surfing the Internet.

 A computer used for engineering applications (CAD/CAM), desktop publishing,
software development, and other such types of applications which require
moderate amount of computing power and relatively high quality graphics
capabilities.
 Workstations generally come with a large, high-resolution graphics screen, large
amount of RAM, inbuilt network support, and a graphical user interface.
 Most workstations also have mass storage device such as a disk drive, but a special
type of workstation, called diskless workstation, comes without a disk drive.
 Common operating systems for workstations are UNIX and Windows NT.
 Workstations are also single-user computers like PC but are typically linked
together to form a local-area network - can be used as stand-alone systems.

 Minicomputer is a midsize multi-processing system capable of
supporting up to 250 users simultaneously.
 Mainframe is very large in size and is an expensive computer
capable of supporting hundreds or even thousands of users
simultaneously.
 Mainframe executes many programs concurrently and supports
many simultaneous execution of programs.
Mini
Computers
Mainframe
Computers

 Supercomputers are the fastest and very expensive computers
currently available.
 Employed for specialized applications that require immense amount
of mathematical calculations (number crunching).
 Example,
weather forecasting, scientific simulations, (animated) graphics, fluid
dynamic calculations, nuclear energy research, electronic design, and
analysis of geological data (e.g. in petrochemical prospecting).

 A computer is made up of only two components:
HARDWARE & SOFTWARE
 HARDWARE: is any part of the computer
has a physical structure. If you can touch it, it is hardware.
 SOFTWARE: the brains of the computer,
is any set of instructions that tells the hardware what to do and helps the user
accomplish a certain task

Hardware consists of two components,
Input and Output devices.
– Input Devices
 An input device allows us to put information into the computer.
Examples include:
Mouse, keyboard, microphone, flash drive or scanner
– Output Devices
 An output device displays (or puts out) information from a computer in either
a visual or auditory format.
Examples include:
Monitor, Speakers, headphones or printer

 Software is a collection of instructions that enable the user to interact
with a computer, its hardware, or perform tasks
 Browsers
– Internet Explorer
– Mozilla Firefox
– Google Chrome
 Games
– Solitaire
 Office
– Word
– Excel
– PowerPoint
 All programs
– Anything listed under all programs and anything you download

 System Software
 Operating System
 Utilities
 Device drivers
 Language translators
 Application software
 Basic application software
 Specialized application software
 General-Purpose Software
 used for a variety of tasks
 Special purpose application software
 to execute one specific task
 Scientific and Business Software
 implementation & simulation, Business &Financial Transaction

 A Programming language is a vocabulary and a set of grammatical
rule for instructing computer or Computing device to perform specific
task.
 The term Programming language usually refers to High Level
Languages like BASIC, C, C++, JAVA, ADA, COBOL, FORTRAN
and PASCAL.

Advantages of machine level language:
 Machine level languages are directly interacting with computer system.
 There is no requirement of software of conversion like compiler or interpreters.
 It takes very less time to execute a program, because there is no conversion take place.
Disadvantages of machine language:
 Its machine dependent language i.e. individual program required for each machine.
 To develop a program in machine language, it’s too hard to understand and program.
 Its time consuming to develop new programs.
 Debugging process is very hard because of finding errors process is typical.
 Machine language is not portable language.

Advantages of Assembly language:
 It is easily understood by human because it is uses statements instead of binary digits.
 To develop a program, it takes less time.
 Debugging and troubleshoot is easy due to easily find error.
 It’s a portable language.
Disadvantages of Assembly language:
 It’s a machine dependent language due to that program design for one machine no use of
other machine.
 Sometime it’s hard to understand the statement or command use.

Advantages of high-level language:
 In this instructions and commands much easier to remember by programmer.
 Its logic and structure are much easier to understand.
 Debugging is easier compare to other languages.
 Less time consuming to writing new programs.
 HLL are described as being portable language.
Disadvantages of high-level language:
 HLL programming language take more space compare to other MLL (machine
level language) and/or ALL (Assembly level language).
 This programming language execute slowly.

 Language Translators are needed to convert High Level Language to
Machine Level Language.
 Whatever language or type of language written in programs are
needed to be converted to machine code in order to be executed by
the computer.
 There are 3 main categories of translator used

 An assembler is a program that translates the mnemonic codes used
in assembly language into the bit patterns that represent machine
operations.
 It is used to convert the assembly language into machine language
(i.e.,0 or 1).
 Assembly language has a one-to-one equivalence with machine
code, each assembly statement can be converted into a single machine
operation.

 A compiler turns the source code that written in a high-level language
into object code (machine code) that can be executed by the
computer.
 Compiler reads whole source code at a time and trap the errors and
inform to programmer.
 The compiler is a more complex than the assembler.
 It may require several machine operations to represent a single
high-level language statement resulting as a lengthy process with very
large programs.

 Interpreters translate the source code at run-time by considering one
statement-at-a-time as the program is executed.
 Converts a high-level language program into machine language by
converting it line-by-line.
 If there is an error in any line during execution, it will report it at the same time
and resume when error is rectified.
 Interpreters are also used with high-level scripting languages like
PHP, JavaScript and many more.
 Instructions are not compiled and have to be interpreted either by the browser (in
the case of JavaScript) or by interpreters on the server (in the case of PHP).

 Linker (Link Editors) is a program in a system which helps to link
an object module of program into a single object file.
 Linking is a process of collecting and maintaining piece of code
and data into a single file.
 Linker also link a particular module into system library.
 It takes object modules from assembler as input and forms an
executable file as output for loader.
 Linking is of two types:
 Static Linking – is performed during the compilation of source program
 Dynamic linking - is performed during the run time

 Linking is performed at both
 compile time - when the source code is translated into machine code and
 load time - when the program is loaded into memory by the loader.
 Linking is performed at the last step in compiling a program.
Source code -> compiler -> Assembler -> Object code -> Linker -> Executable file -> Loader

 Loader is a kind of system software, which is responsible for loading
and relocation of the executable program in the Main Memory.
 It is a part of operating system that brings an executable file
residing on disk into memory and starts its execution process.
 It allocates the memory space to the executable module in main
memory and then transfers control to the beginning instruction of
the program.

 Reading the file and creating an address space for the process.
 Page table entries for the instructions, data and program stack are
created and the register set is initialized.
 Then, executes a jump instruction to the first instruction of the
program which generally causes a page fault and the first page of
your instructions is brought into memory.

 Computer translates letters or words to numbers as computers can
understand only numbers.
 A computer can understand the positional number system where
there are only a few symbols called as Digits and these symbols
represent different values depending on the position they occupy in
the number.
 The value of each digit in a number can be determined using −
 The digit
 The position of the digit in the number
 The base of the number system (where the base is defined as the total number of
digits available in the number system)

SI. No. Number System and Description
1
Decimal Number System
Base 10. Digits used : 0 to 9
2
Binary Number System
Base 2. Digits used : 0, 1
3
Octal Number System
Base 8. Digits used : 0 to 7
4
Hexa Decimal Number System
Base 16. Digits used: 0 to 9, Letters used : A- F

 Decimal number system has base 10 as it uses 10 digits from 0 to 9.
 In decimal number system, the successive positions to the left of the
decimal point represent units, tens, hundreds, thousands, and so on.
 Each position represents a specific power of the base (10).
 For example, the decimal number 1234 consists of the digit
▪ 4 in the units position,
▪ 3 in the tens position,
▪ 2 in the hundreds position, and
▪ 1 in the thousands position.
= (1 x 1000)+ (2 x 100)+ (3 x 10)+ (4 x l)
= (1 x 103)+ (2 x 102)+ (3 x 101)+ (4 x l00)
= 1000 + 200 + 30 + 4
= 1234
Example

 Uses two digits, 0 and 1 and also called as base 2 number system
 Each position in a binary number represents a 0 power of the base (2).
 Example 20
 Last position in a binary number represents a x power of the base (2).
 Example 2x where x represents the last position - 1.
 Example - Binary Number: 101012 to Decimal Equivalent
 Note − 101012 is normally written as 10101.
Step Binary Number Decimal Number
Step 1 101012 ((1 x 2
4
) + (0 x 2
3
) + (1 x 2
2
) + (0 x 2
1
) + (1 x 2
0
))10
Step 2 101012 (16 + 0 + 4 + 0 + 1)10
Step 3 101012 21(10)

 Uses eight digits, 0,1,2,3,4,5,6,7 and also called as base 8 number
system
 Each position in an octal number represents a 0 power of the base (8).
 Example 80
 Last position in an octal number represents a x power of the base (8).
 Example 8x where x represents the last position - 1
 Example - Octal Number: 125708
Step Octal Number Decimal Number
Step 1 125708 ((1 x 8
4
) + (2 x 8
3
) + (5 x 8
2
) + (7 x 8
1
) + (0 x 8
0
))10
Step 2 125708 (4096 + 1024 + 320 + 56 + 0)10
Step 3 125708 549610

 Uses 10 digits and 6 letters, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
 Letters represent the numbers starting from 10.
 A = 10. B = 11, C = 12, D = 13, E = 14, F = 15
 Also called as base 16 number system
 Each position in a hexadecimal number represents a 0 power of the
base (16). Example, 160
 Last position in a hexadecimal number represents a x power of the
base (16). Example 16x where x represents the last position - 1

 Example - Hexadecimal Number: 19FDE16
Step HexaDecimal
Number
Decimal Number
Step 1 19FDE16 ((1 x 16
4
) + (9 x 16
3
) + (F x 16
2
) + (D x 16
1
) + (E x 16
0
))10
Step 2 19FDE16
((1 x 16
4
) + (9 x 16
3
) + (15 x 16
2
) + (13 x 16
1
) + (14 x 16
0
))10
Step 3 19FDE16 (65536+ 36864 + 3840 + 208 + 14)10
Step 4 19FDE16 10646210

 There are many methods or techniques which can be used to convert
numbers from one base to another.
 Decimal to Other Base System
 Other Base System to Decimal
 Other Base System to Non-Decimal
 Shortcut method - Binary to Octal
 Shortcut method - Octal to Binary
 Shortcut method - Binary to Hexadecimal
 Shortcut method - Hexadecimal to Binary

 Step 1 − Divide the decimal number to be converted by the value of
the new base.
 Step 2 − Get the remainder from Step 1 as the rightmost digit (least
significant digit) of the new base number.
 Step 3 − Divide the quotient of the previous divide by the new base.
 Step 4 − Record the remainder from Step 3 as the next digit (to the
left) of the new base number.
 Repeat Steps 3 and 4, getting remainders from right to left, until the
quotient becomes zero in Step 3.
 The last remainder thus obtained will be the Most Significant Digit
(MSD) of the new base number.

Step Operation Result Remainder
Step 1 29 / 2 14 1
Step 2 14 / 2 7 0
Step 3 7 / 2 3 1
Step 4 3 / 2 1 1
Step 5 1 / 2 0 1

 As mentioned in Steps 2 and 4,
 the remainders have to be arranged in the reverse order so that the first remainder
becomes the Least Significant Digit (LSD)
 and the last remainder becomes the Most Significant Digit (MSD).
 Decimal Number : 2910 = Binary Number : 111012.
Step 1 29 / 2 14 1
Step 2 14 / 2 7 0
Step 3 7 / 2 3 1
Step 4 3 / 2 1 1
Step 5 1 / 2 0 1
LSD
MSD

 Step 1 − Determine the column (positional) value of each digit (this
depends on the position of the digit and the base of the number
system).
 Step 2 − Multiply the obtained column values (in Step 1) by the digits
in the corresponding columns.
 Step 3 − Sum the products calculated in Step 2. The total is the
equivalent value in decimal.

Binary Number : 111012 = Decimal Number : 2910
Step Binary
Number
Decimal Number
Step 1 111012 ((1 x 2
4
) + (1 x 2
3
) + (1 x 2
2
) + (0 x 2
1
) + (1 x 2
0
))10
Step 2 111012 (16 + 8 + 4 + 0 + 1)10
Step 3 111012 2910

 Step 1 − Convert the original number to a decimal number (base 10).
 Example - Octal Number : 258
 Step 1 - Convert to Decimal
 Octal Number : 258 = Decimal Number : 2110
Step Octal Number Decimal Number
Step 1 258 ((2 x 8
1
) + (5 x 8
0
))10
Step 2 258 (16 + 5)10
Step 3 258 2110

 Step 2 − Convert the decimal number so obtained to the new base
number.
 Octal Number : 258 = Decimal Number : 2110
 Step 2 - Convert Decimal to Binary
 Decimal Number : 2110 = Binary Number : 101012
 Octal Number : 258 = Binary Number : 101012
Step 1 21 / 2 10 1
Step 2 10 / 2 5 0
Step 3 5 / 2 2 1
Step 4 2 / 2 1 0
Step 5 1 / 2 0 1

 Step 1 − Divide the binary digits into groups of three (starting from
the right).
 Step 2 − Convert each group of three binary digits to one octal digit.
Example - Binary Number : 101012
 Binary Number : 101012 = Octal Number : 258
Step Binary Number Octal Number
Step 1 101012 010 101
Step 2 101012 28 58
Step 3 101012 258

 Step 1 − Convert each octal digit to a 3-digit binary number (the octal
digits may be treated as decimal for this conversion).
 Step 2 − Combine all the resulting binary groups (of 3 digits each)
into a single binary number.
Example - Octal Number : 258
 Octal Number : 258 = Binary Number : 101012
Step Octal Number Binary Number
Step 1 258 210 510
Step 2 258 0102 1012
Step 3 258 0101012

 Step 1 − Divide the binary digits into groups of four (starting from
the right).
 Step 2 − Convert each group of four binary digits to one hexadecimal
symbol.
 Example - Binary Number : 101012
 Binary Number : 101012 = Hexadecimal Number : 1516
Step Binary Number Hexadecimal
Number
Step 1 101012 1 0101
Step 2 101012 110 510
Step 3 101012 1516

 Step 1 − Convert each hexadecimal digit to a 4-digit binary number
(the hexadecimal digits may be treated as decimal for this
conversion).
 Step 2 − Combine all the resulting binary groups (of 4 digits each)
into a single binary number.
 Example - Hexadecimal Number : 1516
 Hexadecimal Number : 1516 = Binary Number : 101012
Step Hexadecimal Number Binary Number
Step 1 1516 110 510
Step 2 1516 00012 01012
Step 3 1516 000101012

• ASCII – PC workstations
• American Standard Code for Information Interchange
• EBCDIC – IBM Mainframes
• Extended Binary Coded Decimal Interchange Code
• Unicode – International Character sets
• Unique, Universal, and Uniform character enCoding.

 ASCII, stands for American Standard Code for Information
Interchange.
 It's a 7-bit character code where every single bit represents a unique
character
 Characteristics/description
 Specifies coding of space and a set of 94 characters (letters, digits and
punctuation or mathematical symbols)
 Suitable for the interchange of basic English language documents.
 Forms the basis for most computer code sets

DEC OCT
HE
X BIN
Symb
ol HTML Number HTML Name Description
0 000 00 00000000 NUL  Null char
1 001 01 00000001 SOH  Start of Heading
2 002 02 00000010 STX  Start ofText
3 003 03 00000011 ETX  End ofText
4 004 04 00000100 EOT  End ofTransmission
5 005 05 00000101 ENQ  Enquiry
6 006 06 00000110 ACK  Acknowledgment
7 007 07 00000111 BEL  Bell
8 010 08 00001000 BS  Back Space
9 011 09 00001001 HT 	 HorizontalTab
10 012 0A 00001010 LF 
 Line Feed
11 013 0B 00001011 VT  VerticalTab
12 014 0C 00001100 FF  Form Feed
13 015 0D 00001101 CR  Carriage Return
14 016 0E 00001110 SO  ShiftOut / X-On
15 017 0F 00001111 SI  Shift In / X-Off

 EBCDIC stands for Extended Binary Coded Decimal Interchange
Code
 Proprietary specification developed by IBM
 Characteristics/description
 A set of national character sets for interchange of documents between IBM
mainframes.
 Most EBCDIC character sets do not contain all of the characters defined in the
ASCII code
 Usage
 Not much used outside of IBM and similar mainframe environments.
 When transmitting EBCDIC files between systems care needs to be taken to
ensure that the systems are set up for the relevant national code set.

 Unicode can represent all of the world's characters in modern
computer use, including technical symbols and special characters
used in publishing.
 Because each Unicode code value is 16 bits wide, it is possible to
have separate values for up to 65,536 characters.
 Unicode-enabled functions are often referred to as "wide-character"
functions.
 Note
 Implementation of Unicode in 16-bit values is referred to as UTF-16.
 For compatibility with 8- and 7-bit environments, UTF-8 and UTF-7 are two
transformations of 16-bit Unicode values.

 The word “algorithm” relates to the name of the mathematician Al-
khowarizmi, which means a procedure or a technique.
 Software Engineer commonly uses an algorithm for planning and
solving the problems.
 An algorithm is a sequence of steps to solve a particular problem or
algorithm is an ordered set of unambiguous steps that produces a
result and terminates in a finite time

 An algorithm is a set of well-defined instructions in sequence to solve
a problem.
 Qualities of a good algorithm
 Input and output should be defined precisely.
 Each step in the algorithm should be clear and unambiguous.
 Algorithms should be most effective among many different ways to solve a
problem.
 An algorithm shouldn't include computer code. Instead, the algorithm should be
written in such a way that it can be used in different programming languages.

 Algorithm has the following characteristics
 Input: An algorithm may or may not require input
 Output: Each algorithm is expected to produce at least one result
 Definiteness: Each instruction must be clear and unambiguous.
 Finiteness: If the instructions of an algorithm are executed, the
algorithm should terminate after finite number of steps

 Three types of control structures.
 1. Sequence: In the sequence structure, statements are placed one after the other
and the execution takes place starting from up to down.
 2. Branching (Selection): In branch control, there is a condition and according
to a condition, a decision of either TRUE or FALSE is achieved. In the case of
TRUE, one of the two branches is explored; but in the case of FALSE condition,
the other alternative is taken. Generally, the ‘IF-THEN’ is used to represent
branch control.
 3. Loop (Repetition): The Loop or Repetition allows a statement(s) to be
executed repeatedly based on certain loop condition e.g. WHILE, FOR loops.

 It is a step-wise representation of a solution to a given problem,
which makes it easy to understand.
 An algorithm uses a definite procedure.
 It is not dependent on any programming language, so it is easy to
understand for anyone even without programming knowledge.
 Every step in an algorithm has its own logical sequence so it is easy
to debug.

 Step 1 - Define your algorithms input
 Step 2 - Define the variables
 Step 3 - Outline the algorithm's operations
 Step 4 - Output the results of your algorithm's operations

 The first design of flowchart goes back to 1945 which was designed by John
Von Neumann.
 Unlike an algorithm, Flowchart uses different symbols to design a solution
to a problem.
 It is another commonly used programming tool.
 By looking at a Flowchart one can understand the operations and sequence
of operations performed in a system.
 Flowchart is often considered as a blueprint of a design used for solving a
specific problem.

 Advantages of flowchart:
 Flowchart is an excellent way of communicating the logic of a program.
 Easy and efficient to analyze problem using flowchart.
 During program development cycle, the flowchart plays the role of a blueprint,
which makes program development process easier.
 After successful development of a program, it needs continuous timely
maintenance during the course of its operation. The flowchart makes program or
system maintenance easier.
 It is easy to convert the flowchart into any programming language code.

 Flowchart is diagrammatic /Graphical representation of sequence
of steps to solve a problem.

 The language used to write algorithm is simple and similar to day-to-
day life language.
 The variable names are used to store the values.
 The value store in variable can change in the solution steps.
 Assignment Symbol (  or =) is used to assign value to the variable.
 e.g. to assign value 5 to the variable HEIGHT,
 statement is
HEIGHT  5
or
HEIGHT = 5

Operator Meaning Example
+ Addition A + B
- Subtraction A – B
* Multiplication A * B
/ Division A / B
^ Power A^3 for A3
% Reminder A % B

< Less than A < B
<= Less than or equal to A <= B
= or == Equal to A = B
# or != Not equal to A # B or A !=B
> Greater than A > B
>= Greater than or equal to A >= B

AND A < B AND B < C Result is True if both
A<B and
B<C are true else false
OR A< B OR B < C Result is True if either
A<B or
B<C are true else fals
NOT NOT (A >B) Result is True if A>B
is false
else true

Selection Control Example Meaning
IF ( Condition ) Then
… ENDIF
IF ( X > 10 ) THEN
Y=Y+5
ENDIF
If condition X>10 is True
execute the statement
between THEN and
ENDIF
IF ( Condition ) Then
… ELSE
…..
ENDIF
IF ( X > 10 ) THEN
Y=Y+5
ELSE Y=Y+8 Z=Z+3
ENDIF
If condition X>10 is True
execute the statement
between THEN and
ELSE otherwise execute
the statements between
ELSE
and ENDIF

Selection Control Example Meaning
WHILE (Condition) DO
..
.. ENDDO
WHILE ( X < 10) DO
print x x=x+1
ENDDO
Execute the loop as long
as the condition is TRUE
DO
….
…
UNTILL (Condition)
DO
print x x=x+1
UNTILL ( X >10)
Execute the loop as long
as the condition is false

 GO TO statement also called unconditional transfer of control
statement is used to transfer control of execution to another
step/statement. .
 e.g. the statement GOTO n will transfer control to step/statement n.
Note:
 We can use keyword INPUT or READ or GET to accept input(s) /value(s) and
keywords PRINT or WRITE or DISPLAY to output the result(s).

Unit 1 computer concepts

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Unit 1 computer concepts