M01_GADD7119_01_SE_C01.QXD 1/30/08 12:55 AM Page 1
CHAPTER
Introduction to Computers
1 and Programming
TOPICS
1.1 Introduction 1.4 How a Program Works
1.2 Hardware and Software 1.5 Using Python
1.3 How Computers Store Data
1.1 Introduction
Think about some of the different ways that people use computers. In school, students use com-
puters for tasks such as writing papers, searching for articles, sending email, and participating in
online classes. At work, people use computers to analyze data, make presentations, conduct busi-
ness transactions, communicate with customers and coworkers, control machines in manufac-
turing facilities, and do many other things. At home, people use computers for tasks such as pay-
ing bills, shopping online, communicating with friends and family, and playing computer games.
And don’t forget that cell phones, iPods®, BlackBerries®, car navigation systems, and many
other devices are computers too. The uses of computers are almost limitless in our everyday lives.
Computers can do such a wide variety of things because they can be programmed. This means
that computers are not designed to do just one job, but to do any job that their programs tell
them to do. A program is a set of instructions that a computer follows to perform a task. For
example, Figure 1-1 shows screens from two commonly used programs, Microsoft Word and
Adobe Photoshop. Microsoft Word is a word processing program that allows you to create,
edit, and print documents with your computer. Adobe Photoshop is an image editing program
that allows you to work with graphic images, such as photos taken with your digital camera.
Programs are commonly referred to as software. Software is essential to a computer because
it controls everything the computer does. All of the software that we use to make our com-
puters useful is created by individuals working as programmers or software developers. A
programmer, or software developer, is a person with the training and skills necessary to
design, create, and test computer programs. Computer programming is an exciting and
rewarding career. Today, you will find programmers’ work used in business, medicine, gov-
ernment, law enforcement, agriculture, academics, entertainment, and many other fields.
1
,M01_GADD7119_01_SE_C01.QXD 1/23/08 5:19 PM Page 2
2 Chapter 1 Introduction to Computers and Programming
Figure 1-1 A word processing program and an image editing program
This book introduces you to the fundamental concepts of computer programming using the
Python language. Before we begin exploring those concepts, you need to understand a few
basic things about computers and how they work. This chapter will build a solid founda-
tion of knowledge that you will continually rely on as you study computer science. First,
we will discuss the physical components that computers are commonly made of. Next, we
will look at how computers store data and execute programs. Finally, we will get a quick
introduction to the software that you will use to write Python programs.
1.2 Hardware and Software
CONCEPT: The physical devices that a computer is made of are referred to as the
computer’s hardware. The programs that run on a computer are referred
to as software.
Hardware
The term hardware refers to all of the physical devices, or components, that a computer is made
of. A computer is not one single device, but a system of devices that all work together. Like the
different instruments in a symphony orchestra, each device in a computer plays its own part.
If you have ever shopped for a computer, you’ve probably seen sales literature listing com-
ponents such as microprocessors, memory, disk drives, video displays, graphics cards, and
so on. Unless you already know a lot about computers, or at least have a friend that does,
understanding what these different components do might be challenging. As shown in
Figure 1-2, a typical computer system consists of the following major components:
• The central processing unit (CPU)
• Main memory
• Secondary storage devices
• Input devices
• Output devices
, M01_GADD7119_01_SE_C01.QXD 1/24/08 7:48 AM Page 3
1.2 Hardware and Software 3
Figure 1-2 Typical components of a computer system
Central Processing
Unit
Output
Devices
Input
Devices
Main Memory
(RAM)
Secondary
Storage Devices
Let’s take a closer look at each of these components.
The CPU
When a computer is performing the tasks that a program tells it to do, we say that the com-
puter is running or executing the program. The central processing unit, or CPU, is the part
of a computer that actually runs programs. The CPU is the most important component in
a computer because without it, the computer could not run software.
In the earliest computers, CPUs were huge devices made of electrical and mechanical
components such as vacuum tubes and switches. Figure 1-3 shows such a device.
The two women in the photo are working with the historic ENIAC computer. The
ENIAC, which is considered by many to be the world’s first programmable electronic
computer, was built in 1945 to calculate artillery ballistic tables for the U.S. Army. This
machine, which was primarily one big CPU, was 8 feet tall, 100 feet long, and weighed
30 tons.
Today, CPUs are small chips known as microprocessors. Figure 1-4 shows a photo of a lab
technician holding a modern microprocessor. In addition to being much smaller than the
old electromechanical CPUs in early computers, microprocessors are also much more
powerful.
CHAPTER
Introduction to Computers
1 and Programming
TOPICS
1.1 Introduction 1.4 How a Program Works
1.2 Hardware and Software 1.5 Using Python
1.3 How Computers Store Data
1.1 Introduction
Think about some of the different ways that people use computers. In school, students use com-
puters for tasks such as writing papers, searching for articles, sending email, and participating in
online classes. At work, people use computers to analyze data, make presentations, conduct busi-
ness transactions, communicate with customers and coworkers, control machines in manufac-
turing facilities, and do many other things. At home, people use computers for tasks such as pay-
ing bills, shopping online, communicating with friends and family, and playing computer games.
And don’t forget that cell phones, iPods®, BlackBerries®, car navigation systems, and many
other devices are computers too. The uses of computers are almost limitless in our everyday lives.
Computers can do such a wide variety of things because they can be programmed. This means
that computers are not designed to do just one job, but to do any job that their programs tell
them to do. A program is a set of instructions that a computer follows to perform a task. For
example, Figure 1-1 shows screens from two commonly used programs, Microsoft Word and
Adobe Photoshop. Microsoft Word is a word processing program that allows you to create,
edit, and print documents with your computer. Adobe Photoshop is an image editing program
that allows you to work with graphic images, such as photos taken with your digital camera.
Programs are commonly referred to as software. Software is essential to a computer because
it controls everything the computer does. All of the software that we use to make our com-
puters useful is created by individuals working as programmers or software developers. A
programmer, or software developer, is a person with the training and skills necessary to
design, create, and test computer programs. Computer programming is an exciting and
rewarding career. Today, you will find programmers’ work used in business, medicine, gov-
ernment, law enforcement, agriculture, academics, entertainment, and many other fields.
1
,M01_GADD7119_01_SE_C01.QXD 1/23/08 5:19 PM Page 2
2 Chapter 1 Introduction to Computers and Programming
Figure 1-1 A word processing program and an image editing program
This book introduces you to the fundamental concepts of computer programming using the
Python language. Before we begin exploring those concepts, you need to understand a few
basic things about computers and how they work. This chapter will build a solid founda-
tion of knowledge that you will continually rely on as you study computer science. First,
we will discuss the physical components that computers are commonly made of. Next, we
will look at how computers store data and execute programs. Finally, we will get a quick
introduction to the software that you will use to write Python programs.
1.2 Hardware and Software
CONCEPT: The physical devices that a computer is made of are referred to as the
computer’s hardware. The programs that run on a computer are referred
to as software.
Hardware
The term hardware refers to all of the physical devices, or components, that a computer is made
of. A computer is not one single device, but a system of devices that all work together. Like the
different instruments in a symphony orchestra, each device in a computer plays its own part.
If you have ever shopped for a computer, you’ve probably seen sales literature listing com-
ponents such as microprocessors, memory, disk drives, video displays, graphics cards, and
so on. Unless you already know a lot about computers, or at least have a friend that does,
understanding what these different components do might be challenging. As shown in
Figure 1-2, a typical computer system consists of the following major components:
• The central processing unit (CPU)
• Main memory
• Secondary storage devices
• Input devices
• Output devices
, M01_GADD7119_01_SE_C01.QXD 1/24/08 7:48 AM Page 3
1.2 Hardware and Software 3
Figure 1-2 Typical components of a computer system
Central Processing
Unit
Output
Devices
Input
Devices
Main Memory
(RAM)
Secondary
Storage Devices
Let’s take a closer look at each of these components.
The CPU
When a computer is performing the tasks that a program tells it to do, we say that the com-
puter is running or executing the program. The central processing unit, or CPU, is the part
of a computer that actually runs programs. The CPU is the most important component in
a computer because without it, the computer could not run software.
In the earliest computers, CPUs were huge devices made of electrical and mechanical
components such as vacuum tubes and switches. Figure 1-3 shows such a device.
The two women in the photo are working with the historic ENIAC computer. The
ENIAC, which is considered by many to be the world’s first programmable electronic
computer, was built in 1945 to calculate artillery ballistic tables for the U.S. Army. This
machine, which was primarily one big CPU, was 8 feet tall, 100 feet long, and weighed
30 tons.
Today, CPUs are small chips known as microprocessors. Figure 1-4 shows a photo of a lab
technician holding a modern microprocessor. In addition to being much smaller than the
old electromechanical CPUs in early computers, microprocessors are also much more
powerful.
