alternate version of starting out with c++ 4 th edition chapter 1 introduction to computers and...
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Alternate Version of STARTING OUT WITH C++ 4th Edition
Chapter 1Introduction to Computers and Programming
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Why Program?• Computer – programmable machine
designed to follow instructions• Program – instructions in computer
memory to make it do something• Programmer – person who writes
instructions (programs) to make computer perform a task
• SO, without programmers, no programs; without programs, the computer cannot do anything
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Computer Systems: Hardware and Software
Main Hardware Component Categories
1. Central Processing Unit (CPU)2. Main Memory3. Secondary Memory / Storage4. Input Devices5. Output Devices
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Main Hardware Component Categories
InputDevice
OutputDevice
SecondaryStorageDevices
CentralProcessing
Unit
MainMemory
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Central Processing Unit (CPU)
Includes Control Unit
Retrieves and decodes program instructions
Coordinates computer operations
Arithmetic & Logic Unit (ALU) Performs mathematical operations
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Main Memory
Holds both program instructions and data
Volatile – erased when program terminates or computer is turned off
Also called Random Access Memory (RAM)
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Main Memory Organization
Bit Smallest piece of memory Stands for binary digit Has values 0 (off, false) or 1 (on, true)
Byte Is 8 consecutive bits Bytes have addresses A byte can hold one character
0 1 1 0 0 1 1 1
8 bits
1 byte
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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, zip disk, hard
drive optical: CD
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Input Devices
Used to send information to the computer from outside
Many devices can provide input keyboard, mouse, scanner, digital
camera, disk drive, CD drive
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Output Devices
Used to send information from the computer to the outside
Many devices can be used for output Computer monitor, printer, disk drive,
writable CD drive
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Software Programs That Run on a Computer
Operating system software programs that manage the computer
hardware and the programs that run on them Ex: Windows, UNIX, Linux
Application software programs that provide services to the user. Ex: word processing, games, programs to solve specific problems
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Programs and Programming Languages
Program a set of instructions directing a
computer to perform a task
Programming Language a language used to write programs
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Programs and Programming Languages
Types of languages Low-level: used for communication
with computer hardware directly. Often written in binary machine code (0’s/1’s).
High-level: closer to human language
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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 to source code program statements.
c) Run compiler to convert source program statements into machine instructions.
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From a High-level Program to an Executable File
d) Run linker to connect hardware-specific code to machine instructions, producing an executable file.
Steps b–d are often performed by a singlecommand or button click.
Errors detected at any step will preventexecution of the following steps.
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From a High-level Program to an Executable File
Object Code
Linker
Executable Code
Source Code
Preprocessor
ModifiedSource Code
Compiler
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What Is a Program Made Of?
Common elements in programming languages Key Words Programmer-Defined Symbols Operators Punctuation Syntax
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Example Program
#include <iostream>#include <string>using namespace std;
int main() {string name;cout << "What is your name? "; cin >> name;cout << "Hello there, " << name;return 0;
}
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Key Words
Also known as reserved words Have a special meaning in C++ Can not be used for another
purpose Examples in program (shown in green): using namespace std; int main()
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Programmer-Defined Symbols
Names made up by the programmer Not part of the C++ language Used to represent various things
variables (memory locations), functions, etc.
Example in program (shown in green): string name;
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Operators
Used to perform operations on data Many types of operators
Arithmetic: +, -, *, / Assignment: =
Examples in program (shown in green): cout << "What is your name? "; cin >> name;
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Punctuation Characters that mark the end of a
statement, or that separate items in a list
Example in program (shown in green):
string name; cin >> name;
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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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Input, Processing, and Output
Three steps many programs perform 1) Gather input data
- from keyboard- from files on disk drives
2) Process the input data3) Display the results as output
- send it to the screen- write to a file
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Software Engineering
Encompasses the whole process of crafting computer software. Specification Design Implementation Test Maintenance
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Flowcharting
Start / Stop Input / Output Process Decision
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Procedural and Object-Oriented Programming
Procedural programming Focus is on the process Procedures/functions are written to process data
Object-Oriented programming Focus is on objects, which contain data and the
means to manipulate the data Messages are sent to objects to perform
operations