Chapter 1 Introduction to
Computers, Programs, and C++
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1
What is a Computer?
A computer consists of a CPU, memory, hard disk, monitor,
printer, and communication devices.
Bus
Storage Communication Input Output
Devices Memory CPU Devices Devices Devices
e.g., Disk, CD, e.g., Modem, e.g., Keyboard, e.g., Monitor,
and Tape and NIC Mouse Printer
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2
CPU
The central processing unit (CPU) is the brain of a computer. It
retrieves instructions from memory and executes them. The CPU
speed is measured in megahertz (MHz), with 1 megahertz equaling 1
million pulses per second. The speed of the CPU has been improved
continuously. If you buy a PC now, you can get an Intel Pentium 4
Processor at 3 gigahertz (1 gigahertz is 1000 megahertz).
Bus
Storage Communication Input Output
Memory CPU Devices Devices Devices
Devices
e.g., Disk, CD, e.g., Modem, e.g., Keyboard, e.g., Monitor,
and Tape and NIC Mouse Printer
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3
Memory
Memory is to store data and program instructions for CPU to
execute. A memory unit is an ordered sequence of bytes, each holds
eight bits. A program and its data must be brought to memory before
they can be executed. A memory byte is never empty, but its initial
content may be meaningless to your program. The current content of
a memory byte is lost whenever new information is placed in it.
Bus
Storage Communication Input Output
Memory CPU Devices Devices Devices
Devices
e.g., Disk, CD, e.g., Modem, e.g., Keyboard, e.g., Monitor,
and Tape and NIC Mouse Printer
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4
How Data is Stored?
Data of various kinds, such as numbers,
characters, and strings, are encoded as a
series of bits (zeros and ones). Computers
use zeros and ones because digital devices Memory address Memory content
have two stable states, which are referred to
as zero and one by convention. The . .
programmers need not to be concerned about . .
the encoding and decoding of data, which is . .
2000 01001010 Encoding for character ‘J’
performed automatically by the system 2001 01100001 Encoding for character ‘a’
based on the encoding scheme. The 2002 01110110 Encoding for character ‘v’
encoding scheme varies. For example, 2003 01100001 Encoding for character ‘a’
character ‘J’ is represented by 01001010 in 2004 00000011 Encoding for number 3
one byte. A small number such as three can
be stored in a single byte. If computer needs
to store a large number that cannot fit into a
single byte, it uses a number of adjacent
bytes. No two data can share or split a same
byte. A byte is the minimum storage unit.
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5
Storage Devices
Memory is volatile, because information is lost when the power is
off. Programs and data are permanently stored on storage devices
and are moved to memory when the computer actually uses them.
There are three main types of storage devices:Disk drives (hard
disks), CD drives (CD-R and CD-RW), and Tape drives.
Bus
Storage Communication Input Output
Memory CPU Devices Devices Devices
Devices
e.g., Disk, CD, e.g., Modem, e.g., Keyboard, e.g., Monitor,
and Tape and NIC Mouse Printer
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6
Output Devices: Monitor
The monitor displays information (text and graphics). The resolution
and dot pitch determine the quality of the display.
Bus
Storage Communication Input Output
Memory CPU Devices Devices Devices
Devices
e.g., Disk, CD, e.g., Modem, e.g., Keyboard, e.g., Monitor,
and Tape and NIC Mouse Printer
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7
Monitor Resolution and Dot Pitch
resolution The resolution specifies the number of pixels per square
inch. Pixels (short for “picture elements”) are tiny dots that
form an image on the screen. The resolution can be set
manually. The higher the resolution, the sharper and
clearer the image is. However, the image may be very
small if you set high resolution on a small screen monitor.
PC monitors are usually 15-inch, 17-inch, 19-inch, or 21-
inch. For a 15-inch monitor, a comfortable resolution
setting would be 640480 (307,200 pixels).
dot pitch The dot pitch is the amount of space between pixels. The
smaller the dot pitch, the better the display.
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8
Communication Devices
A regular modem uses a phone line and can transfer data in a speed up to
56,000 bps (bits per second). A DSL (digital subscriber line) also uses a
phone line and can transfer data in a speed 20 times faster than a regular
modem. A cable modem uses the TV cable line maintained by the cable
company. A cable modem is as fast as a DSL. Network interface card
(NIC) is a device to connect a computer to a local area network (LAN).
The LAN is commonly used in business, universities, and government
organizations. A typical type of NIC, called 10BaseT, can transfer data at
10 mbps (million bits per second).
Bus
Storage Communication Input Output
Memory CPU Devices Devices Devices
Devices
e.g., Disk, CD, e.g., Modem, e.g., Keyboard, e.g., Monitor,
and Tape and NIC Mouse Printer
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9
Programs
Computer programs, known as software, are instructions to
the computer.
You tell a computer what to do through programs. Without
programs, a computer is an empty machine. Computers do
not understand human languages, so you need to use
computer languages to communicate with them.
Programs are written using programming languages.
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10
Programming Languages
Machine Language Assembly Language High-Level Language
Machine language is a set of primitive instructions
built into every computer. The instructions are in
the form of binary code, so you have to enter binary
codes for various instructions. Program with native
machine language is a tedious process. Moreover
the programs are highly difficult to read and
modify. For example, to add two numbers, you
might write an instruction in binary like this:
1101101010011010
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11
Programming Languages
Machine Language Assembly Language High-Level Language
Assembly languages were developed to make
programming easy. Since the computer cannot understand
assembly language, however, a program called assembler is
used to convert assembly language programs into machine
code. For example, to add two numbers, you might write an
instruction in assembly code like this:
ADDF3 R1, R2, R3
Assembly Source File
Machine Code File
…
ADDF3 R1, R2, R3
Assembler …
1101101010011010
…
…
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12
Programming Languages
Machine Language Assembly Language High-Level Language
The high-level languages are English-like and easy to learn
and program. For example, the following is a high-level
language statement that computes the area of a circle with
radius 5:
area = 5 * 5 * 3.1415;
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13
Popular High-Level Languages
COBOL (COmmon Business Oriented Language)
FORTRAN (FORmula TRANslation)
BASIC (Beginner All-purpose Symbolic Instructional Code)
Pascal (named for Blaise Pascal)
Ada (named for Ada Lovelace)
C (whose developer designed B first)
Visual Basic (Basic-like visual language developed by Microsoft)
Delphi (Pascal-like visual language developed by Borland)
C++ (an object-oriented language, based on C)
Java (a popular object-oriented language, similar to C++)
C# (a Java-like developed my Microsoft)
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14
Compiling Source Code
A program written in a high-level language is called a
source program. Since a computer cannot understand a
source program. Program called a compiler is used to
translate the source program into a machine language
program called an object program. The object program is
often then linked with other supporting library code before
the object can be executed on the machine.
Source File Compiler Object File Excutable File
Linker
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15
Operating Systems
The operating system (OS) is
a program that manages and User
controls a computer’s
activities. You are probably Application Programs
using Windows 98, NT, 2000,
XP, or ME. Windows is
Operating System
currently the most popular PC
operating system. Application
Hardware
programs such as an Internet
browser and a word processor
cannot run without an
operating system.
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16
History of C++
C, C++, Java, and C# are very similar. C++ evolved from C. Java was
modeled after C++. C# is a subset of C++ with some features similar to
Java. If you know one of these languages, it is easy to learn the others.
C evolved from the B language and the B language evolved from the
BCPL language. BCPL was developed by Martin Richards in the mid-
1960s for writing operating systems and compilers.
C++ is an extension of C, developed by Bjarne Stroustrup at Bell Labs
during 1983-1985. C++ added a number of features that improved the C
language. Most importantly, it added the object-oriented programming.
An international standard for C++ was created by American National
Standards Institute (ANSI) in 1998 (C++98). C++11 was adopted just
recently.
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17
A Simple C++ Program
Let us begin with a simple C++ program that displays the message
“Welcome to C++!” on the console.
#include <iostream>
using namespace std;
int main()
{
// Display Welcome to C++ to the console
cout << "Welcome to C++!" << endl;
return 0; Note: Clicking the green button displays the source code with
} interactive animation and live run. Internet connection is needed for
this button.
Welcome Note: Clicking the blue button runs the code from Windows. To
enable the buttons, you must download the entire slide file slide.zip
Run and unzip the files into a directory (e.g., c:\slide). If you are using
Office 2010 or higher, check PowerPoint2010.doc located in the
same folder with this ppt file.
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18
C++ IDE Tutorial
You can develop a C++ program from a command window or from
an IDE. An IDE is software that provides an integrated development
environment (IDE) for rapidly developing C++ programs. Editing,
compiling, building, debugging, and online help are integrated in one
graphical user interface. Just enter source code or open an existing
file in a window, then click a button, menu item, or function key to
compile and run the program. Examples of popular IDEs are
Microsoft Visual C++, Dev-C++, Eclipse, and NetBeans. All these
IDEs can be downloaded free.
IDE Supplements on Companion Website
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19
Extending the Simple C++ Program
Once you understand the program, it is easy to extend it to display
more messages. For example, you can rewrite the program to display
three messages, as shown in Listing 1.2.
#include <iostream>
using namespace std;
int main()
{
cout << "Programming is fun!" << endl;
cout << "Fundamentals First" << endl;
cout << "Problem Driven" << endl;
return 0;
}
WelcomeWithThreeMessages Run
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20
Computing with Numbers
Further, you can perform mathematical computations and displays
the result to the console. Listing 1.3 gives such an example.
#include <iostream>
using namespace std;
int main()
{
cout << "(10.5 + 2 * 3) / (45 - 3.5) = ";
cout << (10.5 + 2 * 3) / (45 - 3.5) << endl;
return 0;
}
ComputeExpression Run
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21
Create/Modify Source Code
Creating, Source code (developed by the programmer)
#include <iostream>
using namespace std;
Compiling, and
int main() Saved on the disk
{
// Display Welcome to C++ to the console
cout << "Welcome to C++!" << endl; Source Code
Running }
return 0;
Preprocessor
Programs Stored on the disk
Modified Source
Code
Compiler
If compilation errors
Stored on the disk
An object file (e.g., Welcome.obj) is created. Library Code
Machine Code
program program
Linker
Stored on the disk
An executable file (e.g., Welcome.exe) is created.
Executable Code
Run Executable Code
e.g., Welcome
Result
If runtime errors or incorrect result
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22
Programming Style and
Documentation
Appropriate Comments
Proper Indentation and Spacing
Lines
Block Styles
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23
Programming Errors
Syntax Errors
Runtime Errors
Logic Errors
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24
Syntax Errors
ShowSyntaxErrors
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25
Runtime Errors
ShowRuntimeErrors Run
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26
Logic Errors
ShowLogicErrors Run
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27
Common Errors
Common Error 1: Missing Braces
Common Error 2: Missing Semicolons
Common Error 3: Missing Quotation Marks
Common Error 4: Misspelling Names
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