INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.

CHAPTER ONE

Introduction to computer

What is computer?

A computer is an electronic machine, operating under the control of instructions stored in its own
memory that can accept data, manipulate the data according to specified rules, produce results, and store
the results for future use. Computers process data to create information. Data is a collection of raw or
unprocessed facts, figures, and symbols. Information is data that is organized, meaningful, and useful.
To process data into information, a computer uses hardware and software. Hardware is the electric,
electronic, and mechanical equipment that makes up a computer. Software is the series of instructions
that tells the hardware how to perform tasks.

Characteristics of computer

The characteristics of computers that have made them so powerful and universally useful are speed,
accuracy, diligence, versatility and storage capacity. Let us discuss them briefly.

1. Speed: - Computers work at an incredible speed. A powerful computer is capable of performing

about 3-4 million simple instructions per second. Their speed is measured by the amount of time
it took to perform or carry out a basic operation. Computer speed measured in terms of
microsecond (10-6 one millionths), nanosecond (10-9 one billionths), and Pico second (10-12 one
trillionths).
2. Accuracy: - Nowadays computers are being used for surgical purposes, which need almost a
hundred percent accuracy. From this we can understand that computers are accurate and
consistent. Unless there is an error in the input data or unreliable program the computer
processes with a very high accuracy.
3. Diligence:- Unlike human beings, computers are highly consistent. They do not suffer from
human traits of boredom and tiredness resulting in lack of concentration. Computers, therefore,
are better than human beings in performing voluminous and repetitive jobs.
4. Versatility:- Computers are versatile machines and are capable of performing any task as long
as it can be broken down into a series of logical steps. The presence of computers can be seen in
almost every sphere – Railway/Air reservation, Banks, Hotels, Weather forecasting and many
more.
5. Automatic:- Once necessary information and program is fed, the computer performs processing
without human intervention.
6. Storage capacity:- Today’s computers can store large volumes of data. A piece of information
once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost
instantaneously. And the time it took to retrieve or process single information is not more than a
micro or nanoseconds.

In general a computer has a capacity to store a very large amount of information in organized manner
so that accessing information is very fast.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Types of Computers
Computers can be classified into different categories based on different characteristics.

Based on type of data they process

Based on the type of data they process computers can be classified as:

Analog

Analog computers operate by measuring physical properties. They deal with continuous variables; they
don’t compute directly with numbers, rather, they operate by measuring physical magnitude such as
pressure, temperature, voltage, current etc.

Examples: Thermometer, Voltmeter, Speedometer

Digital

Digital computers deal with discrete variables; they operate by counting rather than measuring. They
operate directly up on numbers (or digits) that represent numbers, letters, or other special symbols.

Examples: Abacus, Desk & pocket calculators, general purpose computers

Hybrid

Hybrid computers inherit the best features of both analog and digital computers. Usually the
Input is continuous data (analog). Since Digital Processing is more accurate, processing takes
place digitally. The processed information – the output – could be either digital or analog,
depending on the user preference or the type of application.

Examples: digital camera, health monitoring machines in some hospitals,

Based on Size, Capacity and price

Size and capacity are also the other characteristics of computers that can be used to categorize computers.
Based on these characteristics computers can be classified as:

Super computer
The term supercomputer has been coined to describe a category of extremely powerful computer designed
for high-speed processing. A supercomputer is generally characterized as being the fastest, most
powerful, and most expensive computer.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Generally, Supercomputers are:

 The largest and the most efficient computers
 Very expensive
 very fast and
 Supports hundreds of users at different locations
Mainframe computer
Mainframe computers are large, powerful computers that are physically larger than micros and minis and
usually have processors with faster instruction processing speeds. For example, they may be able to
process from 10 to 200 million instructions per second (MIPS). Mainframe computers also support
multiple users and are expensive.
Mini computer
Minicomputers are midrange computers that are larger and more powerful than most microcomputers but
are smaller and less powerful than mainframe computer systems. Minicomputers are being used for a
large number of business and scientific applications. They are popularly used in scientific laboratories,
research centers, universities and colleges, engineering firms, industrial process monitoring and control,
etc.
Micro computers
The smallest computers ever produced in the history of computers are microcomputers. Since they are
designed to be used by a single user, they have the least capacity as compared to the other types of
computers. They are also the least expensive of all types. There two different types of microcomputers are
desktop computers and portable computers (laptops, notebook computers and palmtops)

Organization of a computer system

Generally, a computer system is composed of two main components:

1. Computer hardware and

2. Computer software
Computer Hardware
Computer hardware is the physical part of the computer system that can be seen and felt. The hardware
part of a computer system is composed of a number of interacted physical parts. E.g. keyboard, mouse,
CPU

1.1 Types of Computer Hardware

The hardware part of a computer system is composed of a number of interacting physical parts based on
the need of the information flow. Information flows in the computer hardware. There are several criteria
by which computer hardware can be categorized.

Based on information processing, we can divide computer hardware into four:

INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

i) Input Devices
ii) Storage Devices
iii) Output Devices
iv) Central Processing Unit (CPU)

i) Input Devices
Input devices are used to enter information into computer. They convert the data we give them into
the form that can be manipulated in the computer (electronic format).

Some examples of input devices are Keyboard, mouse, scanner, Bar Code Reader, mice

ii) Central Processing Unit

CPU executes instructions and performs the computer's processing activities. It is also known as
processor or microprocessor. It functions the same purpose as the human brain for human being. It is
called the brain of the computer.
One of the basic features of a computer that affects its entire performance is the CPU speed. CPU speed is
measured in Hertz (Hz). Hertz is the number of cycles per second. 1Hz=1cycle per second. Larger units
are KHz (Kilo Hertz), MHz (Mega Hertz), GHz (Giga Hertz), etc.
1 KHz = 1000 Hz

1 MHz = 1000 KHz

1 GHz = 1000MHZ

Current CPUs are as fast as 2-3GHz (2-3 billion cycles per second)

CPU has three sub-components:

 Control Unit (CU)

 Arithmetic Logic Unit (ALU)
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Control Unit

As human brain controls the body, control unit controls the computer hardware. Control Unit
does not execute instruction by itself, i.e. does not carry out instruction processing, but it directs
other processing elements to execute instructions.

Arithmetic Logic Unit (ALU)

The purpose of ALU is to execute instruction. It performs two operations:

 Arithmetic operation
 Logic Operation
Arithmetic operation: this includes mathematical operations like addition, subtraction,
multiplication, division, etc. If you give your computer the instruction 2+3, this will be included
in arithmetic operation and it is executed by Arithmetic Unit.

Logical Operation: this is concerned with the comparison of data and it is called logical
operation. It includes operators like less than, greater than, equal to, less or equal to, greater or
equal to, different from, etc. e.g. if mark>80, grade is 'A'.

iii) Output Devices

Output devices are used to get data out of a computer so that it can be examined, analyzed or distributed
to others. It converts information from machine-understandable form to a human understandable form.
The outputs are of two types: Softcopy: displayed on monitor, projector, or similar devices and Hardcopy:
printed on paper

Examples

 The Visual Display Unit (VDU) or monitor or screen

 Printers (dot matrix, daisy wheel, laser printers)
 Plotters
 Voice (audio) response unit
 Disk drives
iv) Storage Devices
One of the unique features of computers is storage. Data can be stored on different storage media
temporarily or permanently. Storage devices can be categorized into to as:

1. Primary storage device

INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

2. Secondary storage device

1. Primary Memory / Main Memory

Primary memory, also called Main memory, refers to integrated circuit that stores program instructions
and data. The CPU closely works with the main memory to perform its activities. Memory stores three
things:

 Operation system software instructions

 Application software instruction
 Data that is being processed
Depending on the type of information they store and the technology used, the primary memory can be
categorized into three:

 RAM (Random Access Memory)

 ROM (Read Only Memory)
RAM is temporary storage i.e. the data is lost when the computer is off unlike secondary storage.
Because of this it is called volatile memory.

Why is it volatile? It uses electric power to store data. When you write anything on your computer, first it
is stored on RAM. When you save the file, it is transferred into secondary storage.

RAM has differing capacity, the common ones being 128, 256, and 512.It is directly accessible by CPU.
It is called RAM because each memory location can be accessed randomly using memory address. Each
unit in RAM has memory address by which it can be easily accessed/referenced.

ROM stores data and programs that are permanently required by the computer. They have programs built
into them at the factory and that program could not be changed or erased by the user, but read. It is non-
volatile, read-only (not changeable) memory. Read-only means data can't be altered or erased but read.

2. Secondary Storage

Secondary storage (also called auxiliary storage) supplements the primary memory. It takes many forms.
It includes punched cards, punched paper tape, magnetic tape, magnetic disk and optical disk.

Computer Software
Computer hardware is directed by a set of instructions. Without these instructions, computers can do
nothing. These set of instructions are called software (also called programs). One or more programs are
termed as software. We use programming languages to write these instructions. Examples of
programming languages include C, C++, Java, etc.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Software is categorized into two:

 System Software
 Application Software
 System Software
System software consists of programs that are related to controlling the actual operations of the
computer equipment/resource.

There are three types of system software:

 Operating System
 Utility Software
 Language translators
Operating system manage resources, provides a user interface, and run application software. It
organizes resources such as keyboard, mouse, printer, monitor, etc. It also presents GUI (Graphical User
Interface) to the user for easy use of computer. It makes complex hardware more users friendly i.e. it acts
between the user and hardware. Operating system coordinates the activity between the user and the
computer

Utilities software is programs that make computing easier. They perform specific tasks related to
managing computer resources or files. There are different utility programs:

i) Troubleshooting programs: enable us to recognize and correct computer problems before they
become serious.
ii) Anti-virus programs: they protect your computer against viruses or other malicious programs
that damage computer.
iii) File compression programs: are used to reduce the size of files or data so that it takes less
storage space or network band. E.g WinZip, WinRAR, etc.
iv) Uninstall programs: this software enable us to safely and completely remove unneeded
programs/software from your computer.
v) Back up software: with the help of this software, we can make copies of files to be used in
case of the original data is lost/damaged. This copy is called back up.
vi) Screen savers: helps to prevent your work from being seen by others if you leave your
computer idle for some time.
Language translators are used to convert the programming instruction written by users into binary
code that the computer can understand. They are written for specific programming languages and
computer system.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Application Software
Application software performs useful work for the user. These useful works could be:

 Word processing-document creation

 Spreadsheet-electronic calculation
 Data base system
 Email/communicating-email sending and reading
Users use this software to perform different activities like calculation, video editing, word processing,
presentation, etc.

DATA REPRESENTATION IN COMPUTER SYSTEM

Data Representation
Every computer stores numbers, letters, & other special characters in a coded form. But a
computer stores those data’s in a binary number system. There are two main code forms that
every number, letter and special character is represented in a computer system. Before discussing
those codes let have a look at binary number system.
The Binary Number System
Computers are electronic devices that use electrical patterns to represent numbers. Modern digital
computers recognize only two electrical states—ON and OFF— but their memories contain
millions of transistors that can be either on or off. Working with numbers in computers is like
making numbers out of a row of lights that can be switched on and off independently. Because
there are only two ways to represent a number, computers use the binary number system (base 2
or radix 2).
A relationship among Binary & other number system
Decimal Hexadecimal Octal Binary
0 0 0 0
1 1 1 1
2 2 2 10
3 3 3 11
4 4 4 100
5 5 5 101
6 6 6 110
7 7 7 111
8 8 10 1000
INTRODUCTION TO COMPUTER PROGRAMMING 2010 E.C

9 9 11 1001
10 A 12 1010
11 B 13 1011
12 C 14 1100
13 D 15 1101
14 E 16 1110
15 F 17 1111
16 10 20 0001 0000

1.1.1 Why Binary?

Why do we go for binary numbers instead of decimal numbers?’ The reasons are as follows:
1. The 1st reason is that the electronic & electrical components, by their very nature, operate in
a binary mode. Information is handled in the computer by electronic/electrical components such
as transistors, semiconductors, wires, etc all of which can only indicate 2 states or conditions –
on(1) or off(0).
Transistors are either conducting (1) or non conducting (0); a voltage is present (1) or absent (0)
in wire. The binary number system, which has only two digits (0&1), is most suitable for
expressing the two possible states

2. The second reason is that the computer circuits only have to handle two binary digits rather
than ten decimal digits. This greatly simplifies the internal circuit design of computers, resulting
in less expensive & more reliable circuits.

3. Finally, the binary system is used because everything that can be done in decimal number system
(addition, subtraction, division & multiplication) can also be done in binary number system.

1.2 Units of Data Representation

When data is stored, processed, or communicated within the computer system, it is “packed” in units.
Arranged from the smallest to the largest, the units are called bits, bytes, & words.
Bits, Bytes and Words
Bits
A bit is a single binary digit. A bit may have a value of 0 or 1. In a computer, a switch or transistor
that is off represents a 0, and a switch or transistor that is on represents a 1. A bit is represented by the
numbers 1, & 0, which correspond to the states on & off, true & false, or yes & no.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Bytes
Most computers work with groups of 8 bits, which is called a byte. To make it easier to read, the 8
binary digits in a byte are divided into two groups of four, called nibbles, when they are written.

One byte may hold binary numbers ranging in value from 0000 0000 (base 2) to 1111 1111 (base 2),
or from 0 (base 10) to 255 (base 10). Counting 0 as a value, one byte can contain 256 values. For
many computer variables, the maximum value is 255 because the computer wants to store the value in
a single byte, or you are limited to 256 choices.

Words
- Bytes are combined into groups of 1 to 8 bytes called words.
- Words refer to the number of bits that a computer process at once.
- Typically word lengths are 8 bits, 16 bits, 32 bits & 64 bits.

Computer Number systems

A decimal integer is converted to any other base, by using the division operation.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Hexadecimal number system

 Computers use hexadecimal because it represents binary values in a compact form.

 Base 16 number system

 Hex means six, Deci means ten

 16 symbols are used - 0 thru 9, A, B, C, D, E, F

 0-9 = 0-9

 A = 10 D = 13

 B = 11 E = 14

 C = 12 F = 15

Conversion of decimal to hexadecimal

 Reverse the process

 59 is 3B in hexadecimal

 16 goes into 59 three times

 It will take “11” or “B” to get to 59 (59 = 3*16+11) =3 * B (11)

Example: Convert the decimal number 90 into hexadecimal number

Solution:
90 = (5 * 16) +10 this implies 5A because the number 10 is represented by A in hexadecimal.
90 dividing by 16 and collecting the remainder of the digit we can verify it.

 A binary number can be converted into octal or hexadecimal number using a shortcut method.
The shortcut method is based on the following information:-

 An octal digit from 0 to 7 can be represented as a combination of 3 bits, since 23 = 8.

 A hexadecimal digit from 0 to 15 can be represented as a combination of 4 bits, since 24 = 16.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

1.3 Decimal to Other Base System

 Steps 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 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.

1.3.1 Example

Decimal Number: 2910

Calculating Binary Equivalent:

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.

1.4 Other base system to Decimal System

Steps

 Steps 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.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

1.4.1 Example

Binary Number: 111012

Calculating Decimal Equivalent:

Step Binary Number Decimal Number

Step 1 111012 ((1 x 24) + (1 x 23) + (1 x 22) + (0 x 21) + (1 x 20))10

Step 2 111012 (16 + 8 + 4 + 0 + 1)10

Step 3 111012 2910

Binary Number: 111012 = Decimal Number: 2910

1.5 Other Base System to Non-Decimal System

Steps

 Steps 1 - Convert the original number to a decimal number (base 10).

 Step 2 - Convert the decimal number so obtained to the new base number.

1.5.1 Example

Octal Number: 258

Calculating Binary Equivalent:

1.5.2 Step 1: Convert to Decimal

Step Octal Number Decimal Number

Step 1 258 ((2 x 81) + (5 x 80))10

Step 2 258 (16 + 5 )10

Step 3 258 2110

Octal Number: 258 = Decimal Number: 2110

1.5.3 Step 2: Convert Decimal to Binary

Step Operation Result Remainder

Step 1 21 / 2 10 1
INTRODUCTION TO COMPUTER PROGRAMMING 2012E.C

Step 2 10 / 2 5 0

Step 3 5 / 2 2 1

Step 4 2 / 2 1 0

Step 5 1 / 2 0 1

Decimal Number: 2110 = Binary Number: 101012

Octal Number: 258 = Binary Number: 101012

 Shortcut method - Binary to Octal

Steps

 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.

1.5.4 Example

Convert Binary Number: 101012 to Octal Or

Calculating Octal Equivalent:

Step Binary Number Octal Number

Step 1 101012 010 101

Step 2 101012 28 58

Step 3 101012 258

Binary Number: 101012 = Octal Number: 258

1.6 Binary to Octal

An easy way to convert from binary to octal is to group binary digits into sets of three, starting with the
least significant (rightmost) digits.

Binary: 11100101 = 11 100 101

011 100 101 Pad the most significant digits with zeros if
necessary to complete a group of three.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Then, look up each group in a table:

Binary: 000 001 010 011 100 101 110 111

Octal: 0 1 2 3 4 5 6 7

Binary = 011 100 101

Octal = 3 4 5 = 345 oct

 Shortcut method - Octal to Binary

Steps

 Steps 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.

1.6.1 Example

Octal Number: 258

Calculating Binary Equivalent:

Step Octal Number Binary Number

Step 1 258 210 510

Step 2 258 0102 1012

Step 3 258 0101012

Octal Number: 258 = Binary Number: 101012

Converting from octal to binary is as easy as converting from binary to octal. Simply look up each octal
digit to obtain the equivalent group of three binary digits.

Octal: 0 1 2 3 4 5 6 7

Binary: 000 001 010 011 100 101 110 111

INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Octal = 3 4 5

Binary = 011 100 101 = 011100101 binary

 Shortcut method - Binary to Hexadecimal

Steps

 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.

1.6.2 Example

Binary Number: 101012

Calculating hexadecimal Equivalent:

Step Binary Number Hexadecimal Number

Step 1 101012 0001 0101

Step 2 101012 110 510

Step 3 101012 1516

Binary Number: 101012 = Hexadecimal Number: 1516

1.7 Binary to Hexadecimal

An equally easy way to convert from binary to hexadecimal is to group binary digits into sets of four,
starting with the least significant (rightmost) digits.

Binary: 11100101 = 1110 0101

Then, look up each group in a table:

Binary: 0000 0001 0010 0011 0100 0101 0110 0111

Hexadecimal: 0 1 2 3 4 5 6 7

Binary: 1000 1001 1010 1011 1100 1101 1110 1111

Hexadecimal: 8 9 A B C D E F
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Binary = 1110 0101

Hexadecimal = E 5 = E5 hex

Example

Convert the following binary numbers into decimal numbers.

 Conversion of binary number 1010101000010111to hexadecimal number is - AA1716

1.8 Shortcut method - Hexadecimal to Binary

Steps

 Steps 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.

1.8.1 Example

Hexadecimal Number: 1516

Calculating Binary Equivalent:

Step Hexadecimal Number Binary Number

Step 1 1516 110 510

Step 2 1516 00012 01012

Step 3 1516 000101012

Hexadecimal Number: 1516 = Binary Number: 101012

Converting from hexadecimal to binary is as easy as converting from binary to hexadecimal. Simply look
up each hexadecimal digit to obtain the equivalent group of four binary digits.

Hexadecimal: 0 1 2 3 4 5 6 7

Binary: 0000 0001 0010 0011 0100 0101 0110 0111

INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Hexadecimal: 8 9 A B C D E F

Binary: 1000 1001 1010 1011 1100 1101 1110 1111

Hexadecimal = A 2 D E

Binary = 1010 0010 1101 1110 = 1010001011011110 binary

1.9 Octal to Hexadecimal

When converting from octal to hexadecimal, it is often easier to first convert the octal number into binary
and then from binary into hexadecimal. For example, to convert 345 octal into hex:

(From the previous example)

Octal = 3 4 5

Binary = 011 100 101 = 011100101 binary

Drop any leading zeros or pad with leading zeros to get groups of four binary digits (bits):
Binary 011100101 = 1110 0101

Then, look up the groups in a table to convert to hexadecimal digits.

Binary: 0000 0001 0010 0011 0100 0101 0110 0111

Hexadecimal: 0 1 2 3 4 5 6 7

Binary: 1000 1001 1010 1011 1100 1101 1110 1111

Hexadecimal: 8 9 A B C D E F

Binary = 1110 0101

Hexadecimal = E 5 = E5 hex

Therefore, through a two-step conversion process, octal 345 equals binary 011100101 equals hexadecimal
E5.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

1.10 Hexadecimal to Octal

When converting from hexadecimal to octal, it is often easier to first convert the hexadecimal number into
binary and then from binary into octal. For example, to convert A2DE hex into octal:

(From the previous example)

Hexadecimal = A 2 D E

Binary = 1010 0010 1101 1110 = 1010001011011110 binary

Add leading zeros or remove leading zeros to group into sets of three binary digits.

Binary: 1010001011011110 = 001 010 001 011 011 110

Then, look up each group in a table:

Binary: 000 001 010 011 100 101 110 111

Octal: 0 1 2 3 4 5 6 7

Binary = 001 010 001 011 011 110

Octal = 1 2 1 3 3 6 = 121336 octal

Therefore, through a two-step conversion process, hexadecimal A2DE equals binary 1010001011011110
equals octal 121336.

1.11 Hexadecimal to Decimal

Converting hexadecimal to decimal can be performed in the conventional mathematical way, by showing
each digit place as an increasing power of 16. Of course, hexadecimal letter values need to be converted
to decimal values before performing the math.

Hexadecimal: 0 1 2 3 4 5 6 7

Decimal: 012 3 4 5 6 7

Hexadecimal: 8 9 A B C D E F

Decimal: 8 9 10 11 12 13 14 15

A2DE hexadecimal:
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

= ((A) * 163) + (2 * 162) + ((D) * 161) + ((E) * 160)

= (10 * 163) + (2 * 2
16 ) + (13 * 161) + (14 * 160)
= (10 * 4096) + (2 * 256) + (13 * 16) + (14 * 1)
= 40960 + 512 + 208 + 14
= 41694 decimal

1.12 Decimal to Hexadecimal

Here is an example of using repeated division to convert 1792 decimal to hexadecimal:

Hexadecimal
Decimal Number Operation Quotient Remainder
Result

1792 ÷ 16 = 112 0 0

112 ÷ 16 = 7 0 00

7 ÷ 16 = 0 7 700

0 Done.

The only addition to the algorithm when converting from decimal to hexadecimal is that a table must be
used to obtain the hexadecimal digit if the remainder is greater than decimal l 9.

Decimal: 01234567

Hexadecimal: 0 1 2 3 4 5 6 7

Decimal: 8 9 10 11 12 13 14 15

Hexadecimal: 8 9 A B C D E F

Example:
Understanding Kilobytes, Megabytes, and Gigabytes
A kilobyte is often referred to as 1,000 bytes, but this is not totally accurate. In computer terms, a
kilobyte is 1,024 bytes. K is used as shorthand for 210, which equals 1,024.
A megabyte is not exactly 1,000,000 bytes, but 220 bytes, or 1,024 KB, or 1,048,576 bytes. A 200
MB drive can store 204,800 KB or 209,715,200 bytes.
A gigabyte is not 1 billion bytes, but 230 bytes or 1,073,741,824 bytes. 3 GB is the same as
3,221,225,472 bytes.
For Example
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

210 is 1024 1000(or 1KB)

o 1KB (Kilo bytes)-1024 bytes-can store 1,000 characters.
o 1MB = 220 bytes 106 bytes- can store 1 Million characters
o 1GB = 230 bytes  109 bytes – can store 1 Billion characters.
o 1TB= 240 bytes  1012bytes- can store 1 Trillion characters.

 A computer having 256MB of memory is capable of storing 256 * 1048576(220Mega) bytes.

 A floppy disk holds 1.44 MB of data  1, 400, 000 characters.

Programming and Problem Solving

1.1. Programming Languages
Programming Language is a set of rules, symbols, and special words used to construct a computer
program. Programming language rules consists of:
 Rules of Syntax which specify how valid instructions are written in the language.
Rules of Semantics which determine the meaning of the instructions (what the computer will do).
Programming languages are categorized into two main types, these are:
1) Low level languages which in turn include
I. Machine languages and
II. Assembly languages
2) High level languages

Machine Language: is a low level language in which its instructions are string of binary
representation that a computer's hardware can understand and perform.
e.g. 100100 010001
Assembly Language: it is also a low-level programming language in which a mnemonic or a symbol
is used to represent each of the machine language instructions for a specific computer. Assembly
language programs also allow the user to use text names for data rather than having to remember their
memory addresses. The Assembly language is translated into the machine language through an
Assembler.

Table 1.1: Examples of Machine language and Assembly language

High Level Language: The codes in high-level languages are similar to everyday English, closer to
standard notations and it uses ordinary mathematical notations. e.g. C++, Basic, Fortran, Cobol. The
High Level Language is translated to Machine language through Compilers.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Table 1.2 Examples of Assembly language and High level language

1.2. Program Development

Program development involves creating and executing a program. To create and execute a program,
three environments need to be invoked:
 The Editor environment, to create the program source code
 The Compilation environment, to convert a source program into a machine language
 The Execution environment, to run the program
A program consists of a set of instructions written by the programmer. Normally a high level language
(such as C, C++, Pascal, FORTRAN, …) is used to create a plain-text source code.

1.3. Problem Solving Approach

Programming is a process of problem solving that consists of several steps, which include design,
creation, testing and debugging activities. Below are listed the steps recommended for the process of
writing a program.
1. Clearly define the problem.
2. Analyze the problem and formulate a method to solve it
3. Describe the solution in the form of an algorithm.
4. Draw a flowchart or a pseudocode for the algorithm.
5. Write the computer program.
6. Compile and run the program (debugging).
7. Test the program (debugging)
8. Interpret the results.
1.4. Verification and Validation
Every program should be tested to make sure that it does what the programmer intends it to do and that it
actually provides a valid solution to the problem. These tests are commonly divided as:
Verification: verify that program does what you intended it to do; steps 7(8) above attempt to do
this.
Validation: answers the question “does the program actually solve the original problem?” i.e. is
it valid? This goes back to steps 1 and 2 - if you get these steps wrong then your program is not a
valid solution.
1.5. Algorithm
An algorithm is a procedure for solving a problem in terms of the actions to be executed and the order in
which those actions are to be executed. An algorithm is merely the sequence of steps taken to solve a
problem. There are two commonly used tools to help to document an algorithm. These are flowcharts and
Pseudocode. We will use both methods here. Generally, flowcharts work well for small problems but
Pseudocode is used for larger problems.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

1. Pseudocode

Pseudocode is an artificial and informal language that helps programmers develop algorithms.
Pseudocode is similar to natural language, yet close enough to programming language that it can be easily
converted later into program source code. By writing the algorithm in pseudocode first, the programmer
can focus on just the logical steps the program must perform, without having to worry yet about syntax or
about details such as how output will be displayed.
Example 1: Write an algorithm, in pseudocode, for a program that take two numbers and output
the sum of the two numbers.

Algorithm
Step 1: Input two numbers say N1 and N2
Step 2: Calculate the sum N1 + N2
Step 3: out put the sum
Pseudocode
Input N1 and N2
Add N1 and N2
Output N1 and N2

Example 2: Write an algorithm to determine a student’s final mark and indicate whether it is
passing or failing. The final mark is calculated as the average of six marks
Algorithm
Step 1: Input the six marks M1, M2, M3, M4, M5, M6
Step 2: Calculate the average of the six marks
Average = ( M1, M2, M3, M4, M5, M6 )/ 6
Step 3: Check if the Average is greater than 50.
Step 4: if the average is greater than 50 then print (Output) Pass else i.e. if it is below 50 then
print Fail.
Pseudocode
Input M1, M2, M3, M4, M5, M6
Calculate Average= (M1, M2, M3, M4, M5, M6)/ 6
If average is below 50
Print “FAIL”
Else
Print “PASS”
Exercise: Write an algorithm and pseudocode for the following problems
a. Take a number and calculate the factorial of that number
b. Take a number and prints “odd” if the number is odd otherwise prints “even”
c. Calculate the CGPA of a student. (The student should enter grade for the five subjects along
with the respective credit hour).

2. Flowcharts
A flowchart is a diagram that shows the logical flow of a program. It is a useful tool for
planning each operation a program must perform, and the order in which the operations are to
occur. The logical flow of an algorithm can be seen by tracing through the flowchart. Some
standard symbols used in the formation of flow charts are given below.
Flow Chart Symbols
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Example 1: Write an algorithm, in flow chart form that take two numbers and output the
sum of the two numbers.
Algorithm
Step 1: Input two numbers say N1 and N2
Step 2: Calculate the sum N1 + N2
Step 3: out put the sum
Flow chart
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

Example 2: Write an algorithm in flow chart form to determine a student’s final mark and
indicate whether it is passing or failing. The final mark is calculated as the average of six marks.
Flow chart

Example 3: Draw the flow chart for Software development Cycle.

INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C

The flowchart shows the software development cycle. In software development cycle,
you basically design the system, code it and test it. When an error is found, it must be
determined whether the error is a design error or not. Coding errors can quickly be fixed,
but design errors may take longer.
INTRODUCTION TO COMPUTER PROGRAMMING 2012 E.C