Understanding Computers, Smartphones and the Internet

Who is this book for?

Were you ever curious to know how computers work but were afraid to ask? This book is for people who would like to understand how computers work, without having to learn a lot of technical details. There are clear explanations of hardware, software, the Internet and smartphones, using examples and diagrams that are easy to follow.

Chapter 1 follows step by step how a computer program is developed to solve a simple problem and then shows how the hardware runs the program.

Chapter 2 explains how software works, showing with diagrams how software is constructed with many components and layers.

Chapter 3 explains how the Internet works. It shows how a web browser sends a request for a web page using the HTTP protocol and some of the fundamentals of HTML that the browser uses to display a web page.

Chapter 4 explains how Smartphones work. It covers the underlying hardware and radio technology and shows how a mobile phone connects to a network and transmits voice and data.

While originally intended for people who are not in the computer field, this book is also useful for those taking a coding course or an introductory computer science course. Even people already working in computers will find things of interest in this book.

Ernie Dainow

[email protected]

February 2017

Revised January 2025

All rights reserved © 2016 Ernie Dainow

ISBN: 978-0-9952144-0-8

Contents

Who is this book for?

1. What is a Computer?

Basic computer architecture

Start with a problem

Write a program for a solution

Machine Code

Machine Instruction Set

How are machine instructions designed?

Integrated Circuits

Moore’s Law

The Future

2. How Does Software Work?

Computer Languages

Databases

The Layers of Software

Software Development

Software Applications

3. How Does the Internet Work?

What is a Network?

What is the Internet?

How does the Internet work?

What is the Web and how does it work?

HTML (HyperText Markup Language)

Other Protocols

What is the Domain Name System (DNS)?

How is the Internet managed?

4. How Do Smartphones Work?

What is a Smartphone?

Smartphone Hardware

The Network Components

How does radio work?

Smartphone Software

The Cellular Phone Network

Appendix 1. CalculateTax Program

Appendix 2. Binary Numbers, Bits and Bytes

Appendix 3. Internet Routing

Appendix 4. How Does Email Work?

About the Author

1. What is a Computer?

In the context of this book, the word computer can refer to many different sorts of devices. Familiar computers are laptops, desktops and mainframe computers used in large organizations. But computers are found in many other places, such as smartphones, tablets, video game consoles, telephone networks, automobiles, medical equipment, television broadcasting and factories (to name a few). All these computers are fundamentally the same. They are just different sizes and use specialized hardware and software. The description of computers in this book applies to all of these devices.

Basic computer architecture

This diagram is a high-level view of a computer that shows the five main components.

Figure 1-1. Basic computer architecture

Hardware refers to all the physical components in a computer – the CPU (Central Processing Unit), memory chips, disk storage, and various input and output devices.

Software refers to programs that are run on the computer. They are soft because they can be changed without having to modify any of the hardware, which is much more time consuming and expensive.

A special software component is the Operating System (OS) that controls the computer hardware. A computer generally can’t do anything without an OS. When you power on a computer, one of the first things it does is copy the OS from files in Storage into Memory so that they can run in the CPU. Some of the familiar operating systems in use today are Microsoft Windows for PCs, Linux for servers, and Apple iOS or Google Android for smartphones. Once the OS is running, you can then run applications (usually called apps on smartphones), such as a web browser, a text messaging app or a game.

Computer hardware is built by assembling electronic components onto one or more printed circuit boards. The boards have sockets for the components and wired lines that make the necessary electrical connections between them. There are small basic components such as diodes, resistors, capacitors and transistors as well as larger silicon chips, such as memory chips and a CPU chip (marked Amlogic in the figure).

Figure 1-2. Printed Circuit Board

CPU is the Central Processing Unit. This is the brain of the computer. It controls the operations in all the other components and it makes all the decisions. Many computers use an Intel processor chip for the CPU. Smartphones and tablets use a variety of smaller CPU chips.

The CPU generally needs two things: a program (code) and data.

A program, or application, is the list of instructions that tells the computer what to do.

Data is information that a program processes, typically information provided from an Input device or from a file in Storage.

All computations done by a computer can only be done on data that is in a register in the CPU. These registers are very expensive to build so even large computers do not have very many.

Input includes such familiar devices as a keyboard, mouse or a touchscreen.

Output is where the computer’s results are sent. On a PC or mobile phone, this is typically your display screen. But it can also be a printer or a network, like the Internet. A network can also be an input device.

Storage is where programs and data are saved. Data includes documents created by different programs, music files, video files and system files. Storage for many years was a hard disk drive but is now generally an SSD (solid state drive), a storage device that uses flash memory. On computers you generally need to manage Storage to create and delete folders and files and copy files from one folder to another. Smartphone apps generally manage Storage automatically and you rarely need to do very much file management.