U 1
T T O R I A L
Advanced Painter Application
Introducing Computers, the Internet and Visual Basic
2009 Pearson Education, Inc. All rights reserved.
1
2
Outline
1.1 1.2 1.3 1.4 1.5 1.6 What Is a Computer? Computer Organization Machine Languages, Assembly Languages and High-Level Languages Visual Basic Other High-Level Languages Structured Programming
2009 Pearson Education, Inc. All rights reserved.
3
Outline
1.7 1.8 1.9 1.10 Key Software Trend: Object Technology The Internet and the World Wide Web Introduction to Microsoft .NET Test-Driving the Visual Basic Advanced Painter Application
2009 Pearson Education, Inc. All rights reserved.
4
1.1 What Is a Computer? A computer is a device that can perform calculations and make logical decisions much faster than humans can. Computers process data, using sets of instructions called computer programs.
These programs guide computers through orderly sets of actions that are specified by people known as computer programmers.
2009 Pearson Education, Inc. All rights reserved.
5
1.1 What Is a Computer? (Cont.)
A computer is composed of various devices known as hardware:
keyboard screen mouse hard drives memory DVD drives printer processing units
The programs that run on a computer are referred to as software.
2009 Pearson Education, Inc. All rights reserved.
6
1.2 Computer Organization Computers can be thought of as being divided into six units:
Input unit: This "receiving" section of the computer obtains information from input devices.
Input can come from devices such as the keyboard and the mouse.
Output unit: This "shipping" section of the
computer takes information that the computer has processed and places it on various output devices.
Output can be displayed on screens, printed on paper, played on audio/video devices, and transmitted over the Internet.
2009 Pearson Education, Inc. All rights reserved.
7
1.2 Computer Organization (Cont.)
Memory unit: This "warehouse" section of the computer stores data while an application is running. Its information is immediately available for processing.
To be executed, computer programs must be in memory. The memory unit retains information until it can be sent to output devices. Often, the memory unit is called either memory or primary memory. Random-access memory (RAM) is an example of primary memory. Primary memory is usually volatile, which means that it is erased when the machine is powered off.
2009 Pearson Education, Inc. All rights reserved.
8
1.2 Computer Organization (Cont.)
Central processing unit (CPU): The CPU supervises the operation of the other sections. Arithmetic and logic unit (ALU): The ALU (a part of the CPU) performs calculations and makes decisions. Secondary storage unit: This unit is the "warehousing" section of the computer.
Devices such as hard drives, CD-ROM drives, DVD drives, and USB memory sticks are secondary storage units. These normally hold programs or data that other units are not actively being used. The computer can retrieve this information when it is needed later in time. Secondary storage is nonvolatile. Information in secondary storage takes much longer to access than information in primary memory.
2009 Pearson Education, Inc. All rights reserved.
1.3 Machine Languages, Assembly Languages and High-Level Languages
9
Programmers write instructions in programming languages. Some of these are directly understandable by computers, and others require intermediate translation steps. Computer languages that are in use today can be divided into three general types:
machine languages assembly languages high-level languages
2009 Pearson Education, Inc. All rights reserved.
1.3 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
10
A computer can directly understand only its own machine language. As the "natural language" of a particular computer, machine language is defined by the computer's hardware design. Machine languages are machine dependent. Machine languages generally consist of streams of numbers (ultimately reduced to 1s and 0s in the binary number system).
2009 Pearson Education, Inc. All rights reserved.
1.3 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
11
The following section of a machine-language program demonstrates the incomprehensibility of machine language to humans:
[phone] [phone] [phone]
Machine-language programming proved to be slow and error prone.
2009 Pearson Education, Inc. All rights reserved.
1.3 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
12
Programmers began using English-like abbreviations to represent the computer's basic operations. These abbreviations formed the basis of assembly languages.
LOAD BASEP AY ADD OVERP AY STORE GROSSP AY
2009 Pearson Education, Inc. All rights reserved.
1.3 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
13
Translator programs called assemblers convert assembly-language programs to machine language. Although it is clearer to humans, computers cannot understand assembly-language code until it is translated into machine language. Assembly languages still require many instructions to accomplish even the simplest tasks.
2009 Pearson Education, Inc. All rights reserved.
1.3 Machine Languages, Assembly Languages and High-Level Languages (Cont.)
14
To speed up the programming process, high-level languages were developed. Programs called compilers convert high-levellanguage programs into machine language. High-level languages look almost like everyday English and contain common mathematical notations.
grossP ay = baseP ay + overT imeP ay
Visual Basic is one of the world's most popular high-level programming languages.
2009 Pearson Education, Inc. All rights reserved.
15
1.4 Visual Basic Visual Basic evolved from BASIC (Beginner's All-purpose Symbolic Instruction Code), which was developed as a language for writing simple programs quickly and easily. When Bill Gates founded Microsoft Corporation in the 1970s, he implemented BASIC on several early personal computers.
2009 Pearson Education, Inc. All rights reserved.
16
1.4 Visual Basic (Cont.) In the late 1980s and the early 1990s, Microsoft developed the Microsoft Windows graphical user interface (GUI). Visual Basic was introduced by Microsoft in 1991 to make programming Windows applications easier.
2009 Pearson Education, Inc. All rights reserved.
17
1.4 Visual Basic (Cont.)
Visual Basic is a so-called object-oriented, event-driven visual programming language. Programs are created with the use of a software tool called an Integrated Development Environment (IDE). The latest versions of Visual Basic are fully object oriented and respond to user-initiated events such as mouse clicks, keystrokes and timers. In Visual Studio, it is convenient to make programs by dragging and dropping predefined objects like buttons and textboxes.
2009 Pearson Education, Inc. All rights reserved.
18
1.4 Visual Basic (Cont.) Microsoft introduced its .NET strategy in 2000. The .NET platform allows applications to be distributed to a variety of devices. Software components created in different .NET programming languages can communicate with one another.
2009 Pearson Education, Inc. All rights Other reserved.
19
1.5 High-Level Languages Although hundreds of high-level languages have been developed, only a few have achieved broad acceptance. IBM Corporation developed Fortran in the mid-1950s to create scientific and engineering applications. COBOL was developed in the late 1950s by a group of computer manufacturers. COBOL is used primarily for business applications that require the manipulation of large amounts of data.
2009 Pearson Education, Inc. All rights reserved.
20
1.5 Other High-Level Languages (Cont.)
The C language gained widespread recognition as a development language for the UNIX operating system. C++ was developed by Bjarne Stroustrup in the early 1980s at Bell Laboratories. C++ provides capabilities for object-oriented programming (OOP).
Objects are reusable software components that model items in the real world. Object-oriented programs are easier to understand, correct and modify.
2009 Pearson Education, Inc. All rights reserved.
21
1.5 Other High-Level Languages (Cont.) Developers use Java to create web pages with dynamic content, to build large-scale enterprise applications, to enhance the functionality of web servers, and to provide applications for consumer devices. In 2000, Microsoft announced C#. The C# programming language was designed specifically for the .NET platform. Like Visual Basic, C# is object oriented and has access to .NET's library.
2009 Pearson Education, Inc. All rights reserved.
22
1.6 Structured Programming
During the 1960s, software-development efforts often ran behind schedule, costs greatly exceeded budgets and the finished products were unreliable. Research activity intended to address these issues resulted in the evolution of structured programming. Pascal was designed for teaching structured programming, but lacks many features needed to make it useful in commercial, industrial and government applications. The Ada programming language, based on Pascal, was developed under the sponsorship of the U.S. Department of Defense (DOD) during the 1970s and early 1980s.
2009 Pearson Education, Inc. All rights reserved.
23
1.7 Key Software Trend: Object Technology Object technology is a packaging scheme for creating meaningful software units. Almost any noun can be reasonably represented as a software object. Objects:
have properties such as color, size and weight perform actions such as moving, sleeping or drawing
A class specifies the general format of its objects, and the properties and actions available to an object depend on its class.
2009 Pearson Education, Inc. All rights reserved.
24
1.7 Key Software Trend: Object Technology (Cont.)
Procedural programming languages focused on actions (verbs) rather than objects (nouns). Object-oriented languages more naturally reflects the way in which we perceive the world. This has resulted in significant productivity gains.
Properly designed classes can be reused on future projects Using libraries of classes reduces the amount of effort required to implement new systems The production of software is more understandable because it is better organized and has fewer maintenance requirements.
2009 Pearson Education, Inc. All rights reserved.
25
1.7 Key Software Trend: Object Technology (Cont.) Instead of worrying about the details of how objects are implemented, you can focus on the behaviors and interactions of objects. Visual Basic is one of the world's most widely used object-oriented languages.
2009 Pearson Education, Inc. All rights reserved.
26
1.8 The Internet and the World Wide Web In the late 1960s, ARPA rolled out plans to network the main computer systems of ARPAfunded universities and research institutions. This became known as the ARPAnet, the grandparent of today's Internet. Its main benefit proved to be the capability for quick and easy communication via what came to be known as electronic mail (e-mail).
2009 Pearson Education, Inc. All rights reserved.
27
1.8 The Internet and the World Wide Web (Cont.)
The protocol for communicating over the ARPAnet became known as the Transmission Control Protocol (TCP). TCP ensured that messages, consisting of pieces called "packets," were properly routed from sender to receiver, arrived intact and were assembled in the correct order. One challenge was to enable different networks to communicate with each other.
ARPA accomplished this by developing the Internet ...