chapter 1. introduction to computers and programming

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Starting Out with C++, 3rd Edition

Chapter 1. Introduction to Computers and Programming

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1.1 Why Program?

• Computers can do many different jobs because they are programmable.

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1.2 Computer Systems: Hardware and Software

• All computer systems consist of similar hardware devices and software components. This section provides an overview of standard computer hardware and software organization.

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Hardware

1. The CPU

2. Main Memory

3. Secondary Storage

4. Input Devices

5. Output Devices

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InputDevice

CentralProcessing

Unit

MainMemory

OutputDevice

OutputDevice

Figure 1.1

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Figure 1.2

Arithmetic and Logic

Unit

Control Unit

Instruction(Input)

Result(Output)

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Software

– Operating Systems• Single tasking

• Multi-tasking

– Application Software

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1.3 Programs and Programming Languages

• What is a program?– A set of instructions a computer follows in

order to perform a task. A programming language is a special language used to write computer programs.

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Program 1-1

// This program calculates the user’s pay.

#include <iostream.h>

void main(void)

{

float hours, rate, pay;

cout << “How many hours did you work? ”;

cin >> hours;

cout << “How much do you get paid per hour? ”;

cin >> rate;

pay = hours * rate;

cout << “You have earned $” << pay << endl;

}

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Program Output

How many hours did you work? 10How much do you get paid per hour? 15You have earned $150

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Programming Languages

High level(Close to Human

Language)

Low level(Machine Language)

• Figure 1-4

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Table 1-1Language DescriptionBASIC Beginners All-purpose Symbolic Instruction Code.

A general programming language originallydesigned to be simple enough for beginners to learn.

FORTRAN Formula Translator. A language designed forprogramming complex mathematical algorithms.

COBOL Common Business-Oriented Language. A languagedesigned for business applications.

Pascal A structured, general purpose language designedprimarily for teaching programming.

C A structured, general purpose language developed atBell Labs. C offers both high-level and low-levelfeatures.

C++ Based on the C language, C++ offers object-orientedfeatures not found in C. Also invented at BellLaboratories.

Java An object-oriented language invented at SunMicrosystems. Java may be used to developprograms that run over the Internet, in a webbrowser.

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1.4 What is a Program Made of?• There are certain elements that are common

to all programming languages.– Key Words– Programmer-Defined Symbols– Operators– Punctuation

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Language Elements, Table 1-2LanguageElement

Description

Key Words Words that have a special meaning. Keywords may only be used for their intendedpurpose.

Programmer-DefinedSymbols

Words or names defined by the programmer.They are symbolic names that refer tovariables or programming routines.

Operators Operators perform operations on one or moreoperands. An operand is usually a piece ofdata, like a number.

Punctuation Punctuation characters that mark thebeginning or ending of a statement, orseparate items in a list.

Syntax Rules that must be followed whenconstruction a program. Syntax dictates howkey words and operators may be used, andwhere punctuation symbols must appear.

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Lines and Statements

cout << “How many hours did you work?”;

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Variables

• A storage location in the computer’s memory for holding a piece of information.

• Symbolic names that represent locations in the computer’s random-access memory.

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Variable Declarations

• Two types of information: numbers and characters

• Numbers may be integers or floating-point numbers

• The statement below creates three variables in memory named hours, rate, and pay that each can store a floating point number

float hours, rate, pay;

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1.5 Input, Processing, and Output

• Input:cin >> hours;

• Processing:pay = hours * rate;

• Outputcout<<“You have earned $”<<pay;

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1.6 The Programming Process

• The programming process consists of several steps, which include design, creation, testing and debugging activities.

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Designing and Creating a Program

1. Clearly define what the program is to do

2. Visualize the program running on the computer.

3. Design a flowchart or hierarchy chart

4. Check the flowchart or hierarchy chart for logical errors.

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5. Write a pseudocode version of the program.

6. Check the pseudocode for errors.

7. Write the actual program on paper.

8. Desk-check the program for errors.

9. Enter the code and compile it.

10. Correct any errors found during compilation. Repeat steps 9 and 10 as many times as necessary.

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11. Run the program with test data for input.

12. Correct any errors found while running the program. Repeat steps 9 through 12 as many times as necessary.

13. Validate the results of the program.

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1.7 Procedural and Object-Oriented Programming

• Procedural programming and object-oriented programming are two ways of thinking about software development and program design.

chapter 1. introduction to computers and programming

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