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INTRODUCTION TO
COMPUTERS ANDPROGRAMMING
Chapter 01
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1.1 Why Program?2
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Why Program?
Computerprogrammable machine designed to
follow instructions
Programinstructions in computer memory to
make it do somethingProgrammerperson who writes instructions
(programs) to make computer perform a task
SO, without programmers, no programs; without
programs, a computer cannot do anything
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1.2 Computer Systems: Hardware
and Software4
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Main Hardware Component
Categories:
1. Central Processing Unit (CPU)
2. Main Memory
3. Secondary Memory / Storage
4. Input Devices
5. Output Devices
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Main Hardware Component
Categories
Figure 1-1
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Central Processing Unit (CPU)
Comprised of:
Control UnitRetrieves and decodes program instructions
Coordinates activities of all other parts of computerArithmetic & Logic Unit
Hardware optimized for high-speed numeric calculation
Hardware designed for true/false, yes/no decisions
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Main Memory
AddressesEach byte in memory is identified by
a unique number known as an address.
Above figure, the number 149 is stored in the byte with the address 16, and thenumber 72 is stored at address 23.
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Secondary Storage
Non-volatile: data retained when program is
not running or computer is turned off
Comes in a variety of media:
magnetic: floppy disk, hard drive
optical: CD-ROM, DVD
Flash drives, connected to the USB port
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Input Devices
Devices that send information to the computer
from outside
Many devices can provide input:
Keyboard, mouse, scanner, digital camera,microphone
Disk drives, CD drives, and DVD drives
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Output Devices
Output is information sent from a computer
program to the outside world.
The output is sent to an output device
Many devices can be used for output:
Computer monitor and printer
Disk drives
Writable CD and DVD drives
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SoftwarePrograms That Run
on a Computer
Categories of software:
Operating system: programs that manage thecomputer hardware and the programs that run onthem. Examples: Windows, UNIX, Linux
Application software: programs that provideservices to the user. Examples: word processing,games, programs to solve specific problems
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1.3 Programs and Programming
Languages15
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Programs and
Programming Languages
A program is a set of instructions that the
computer follows to perform a task
We start with an algorithm, which is a set of
well-defined steps.
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Example Algorithm for
Calculating Gross Pay
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Machine Language
Although the previous algorithm defines the
steps for calculating the gross pay, it is not
ready to be executed on the computer.
The computer only executes machinelanguageinstructions.
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Machine Language
Machine language instructions are binary
numbers, such as
1011010000000101
Rather than writing programs in machine
language, programmers useprogramming
languages.
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Programs and
Programming Languages
Types of languages:
Low-level: used forcommunication with computerhardware directly. Often writtenin binary machine code (0s/1s)directly.
High-level: closer to humanlanguage
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Some Well-Known Programming
Languages (Table 1-1 on Page 9)
BASIC
FORTRAN
COBOL
C
C++
C#
Java
JavaScript
Python
Ruby
Visual Basic
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From a High-level Program to an
Executable File
a) Create file containing the program with a text editor.
b) Run preprocessor to convert source file directives tosource code program statements.
c) Run compiler to convert source program into machineinstructions.
d) Run linker to connect hardware-specific code tomachine instructions, producing an executable file.
Steps bd are often performed by a single commandor button click.
Errors detected at any step will prevent execution offollowing steps.
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From a High-level Program to an
Executable File
Source Code
Preprocessor
ModifiedSource Code
Compiler
Object Code
Linker
Executable Code
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Integrated Development
Environments (IDEs)
An integrated development environment, or
IDE, combine all the tools needed to write,
compile, and debug a program into a single
software application. Examples are Microsoft Visual C++, Turbo
C++ Explorer, CodeWarrior, etc.
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Integrated Development
Environments (IDEs)
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1.4 What Is a Program MadeOf?
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What Is a Program Made Of?
Common elements in programminglanguages:
Key Words
Programmer-Defined IdentifiersOperators
Punctuation
Syntax
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Program 1-1
1 // This program calculates the user's pay.2 #include 3 using namespace std;45 int main()6 {7 double hours, rate, pay;8
9 // Get the number of hours worked.10 cout > hours;1213 // Get the hourly pay rate.14 cout > rate;
1617 // Calculate the pay.18 pay = hours * rate;1920 // Display the pay.21 cout
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Key Words
Also known as reserved words
Have a special meaning in C++
Can not be used for any other purpose
Key words in the Program 1-1: using,
namespace, int, double, and return.
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1 // This program calculates the user's pay.2 #include 3 using namespace std;45 int main()6 {7 double hours, rate, pay;
89 // Get the number of hours worked.10 cout > hours;1213 // Get the hourly pay rate.14 cout > rate;
1617 // Calculate the pay.18 pay = hours * rate;1920 // Display the pay.21 cout
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P D fi d
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1 // This program calculates the user's pay.2 #include 3 using namespace std;45 int main()6 {7 double hours, rate, pay;
89 // Get the number of hours worked.10 cout > hours;1213 // Get the hourly pay rate.14 cout > rate;
1617 // Calculate the pay.18 pay = hours * rate;1920 // Display the pay.21 cout
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Operators
Used to perform operations on data
Many types of operators:
Arithmetic - ex: +,-,*,/
Assignmentex: =
Some operators in Program1-1:
> = *
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Operators
1 // This program calculates the user's pay.2 #include 3 using namespace std;45 int main()6 {7 double hours, rate, pay;
89 // Get the number of hours worked.10 cout > hours;1213 // Get the hourly pay rate.14 cout > rate;
1617 // Calculate the pay.18 pay = hours * rate;1920 // Display the pay.21 cout
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Punctuation
Characters that mark the end of a statement,
or that separate items in a list
In Program 1-1: ,and ;
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Syntax
The rules of grammar that must be followed
when writing a program
Controls the use of key words, operators,
programmer-defined symbols, and punctuation
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Variables
A variable is a named storage location in thecomputers memory for holding a piece ofdata.
In Program 1-1 we used three variables: The hoursvariable was used to hold the
hours worked
The ratevariable was used to hold the pay
rate Thepayvariable was used to hold the gross
pay
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Variable Definitions
To create a variable in a program you must write
a variable definition (also called a variable
declaration)
Here is the statement from Program 1-1 that
defines the variables:
double hours, rate, pay;
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Variable Definitions
There are many different types of data, whichyou will learn about in this course.
A variable holds a specific type of data.
The variable definition specifies the type ofdata a variable can hold, and the variable
name.
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Variable Definitions
Once again, line 7 from Program 1-1:
double hours, rate, pay;
The word doublespecifies that the variables
can hold double-precision floating point
numbers. (You will learn more about that in
Chapter 2)
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1.5 Input, Processing, andOutput
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Input, Processing, and Output
Three steps that a program typically performs:
1) Gather input data: from keyboard
from files on disk drives
2) Process the input data
3) Display the results as output: send it to the screen
write to a file
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The Programming Process