CS 102: Section 1 Sussan Einakian

Objectives

 Basic Computer Concepts  Computer Organization  Computer Software/ Hardware  Programming Languages  The elements of C program environment For some sample programs you can check the authors website: www.deitel.com/books/chtp7/

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What is a Computer?

• Computer – Device capable of performing computations and making logical decisions million times faster than human.

– Computers process data.

– Today’s fastest supercomputers can perform thousands of trillions (quadrillions) of instructions per second! – Computer can perform more than 100,000 calculations per second for every person on the planet!

Use of Computer

            Electronic health record Human Genome Project Amber Alert World Community Grid Medical Imaging One Laptop per Child Cloud Computing GPS Robots Email, Instant Messaging, Video Chat, FTP Internet TV Game Programming

Hardware-Software

 There are more than a billion general-purpose computers, and billions more

embedded

computers are used in cell phones, smart phones, tablet computers, home appliances, automobiles and more  Hardware  A computer consist of various devices.

 Keyboard, screen, mouse, disks, memory, CD-ROM, and etc.

 Software  Programs that run on a computer.

 Computers process data based on sets of instructions called computer programs.

Computers Before and Now

 Computers that might have filled large rooms and cost millions of dollars decades ago are now inscribed on silicon chips smaller than a fingernail, costing perhaps a few dollars each.  Silicon-chip technology has made computing so economical that more than computers have become a commodity.  For many decades, hardware costs have fallen rapidly.  Every year or two, the capacities of computers have approximately

doubled

without any increase in price.

 This remarkable trend often is called Moore’s Law , named for the person who identified it, Gordon Moore, co-founder of Intel.

Information-processing cycle

 Consists of four basic operations:  Input    Processing Output Storage

Early Computers

For more information on early computers you can check this link:

http://www.computersciencelab.com/ComputerHistory/HistoryPt4.htm

IBM Card Punch or Batch Computing

The Von Neumann-Eckert Model

The famous mathematician John Von Neumann , that proposed the stored program concept (in 1945).

often called Father of Modern Computing

Computer Organization (Logical Units)

1) Input 2) Output 3) CPU 4) ALU 5) Memory 6) Secondary Storage

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Computer Organization

 Regardless of differences in physical appearance, computers can be envisioned as divided into various logical units or sections: 1.

2.

3.

4.

5.

Input unit (Receiving Section)  Obtains information from input devices (keyboard, mouse touch, voice) Output unit (Shipping Section)  Outputs information (to screen, to printer, to control other devices) Memory unit (Warehouse Section)  Rapid access, low capacity, stores input information (called as primary memory) Arithmetic and logic unit (ALU) (Manufacturing Section)  Performs arithmetic calculations and logic decisions Central processing unit (CPU) (Administrative Section)  Supervises and coordinates the other sections of the computer 6.

Secondary storage unit   Cheap, long-term, high-capacity storage, persitent Stores inactive programs

Personal Computing, Distributed Computing, and Client/Server Computing

 Personal computers (from 1977)  Economical enough for individual  Distributed computing  Computing distributed over networks  Client/server computing  Sharing information across computer networks between file servers and clients (personal computers) 16

New Generation of Computers



A single finger, multi-touch computer screens can follow the instructions of many fingers simultaneously.



A wall-size screen developed by Perceptive Pixel can respond to as many as 10 fingers or multiple hands.

New Computers

Combined with the newest wireless technology, prepare for computers to be even more available than they are now.

New Generation of Sony Computers by 2020

Computer Software

 The programs that allow the computer hardware to operate.  System Software:  Operating Systems, language translators, and utilities (Editors, Software used to create, copy , delete files).  Application Software  The type of program you will learn to write in this class.

Operating System

The OS as a Conductor

The OS

coordinates the sharing and use

of all the components in the computer 25

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Operating Systems

Operating Systems  Manage smooth transitions between jobs  Increased throughput  Amount of work computers process  Batch processing (Early Computers)   Do only one job or task at a time Submit the jobs to computer center  Multitasking  Computer resources are shared by many jobs or tasks  Timesharing  Computer runs a small portion of one user’s job then moves on to service the next user

Operating System

 The software that contains the core components of the operating system is called the kernel .  Popular desktop operating systems include Linux, Unix, Windows, and Mac OS X.  Popular mobile operating systems used in smartphones and tablets include Google’s Android, Apple’s iOS (for iPhone, iPad and iPod Touch devices), BlackBerry OS and Windows Phone 7 and 8.

Application Software

Programmers write instructions in various programming languages, some directly understandable by computers and others requiring intermediate

translation

steps. 28 Three types of programming languages 1.

2.

Machine languages  Strings of numbers giving machine specific instructions  Example: +1300042774 +1400593419 +1200274027 Assembly languages   English-like abbreviations representing elementary computer operations (translated via assemblers) Example: LOAD BASEPAY ADD OVERTIMEPAY STORE SALARY

High-level Languages

  Computer usage increased rapidly.

3.

 To speed up programming process.

High-level languages  Codes similar to everyday English  Use mathematical notations (translated via compilers)  Example:  Salary = basePay + overTimePay Interpreter programs were developed to execute high-level language programs directly, although more slowly than compiled programs.  Scripting languages such as JavaScript and PHP are processed by interpreters. 29

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High Level Languages

• Fortran (Formula Translator) – developed by IBM Corporation in the 1950s – used for scientific and engineering applications that require complex mathematical computations • COBOL (Common Business Oriented Language) – developed in 1959 by computer manufacturers, the government and industrial computer users – used for commercial applications that require precise and efficient manipulation of large amounts of data

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High Level Languages

 Pascal  Developed by Professor Niklaus Wirth in 1971  Designed for teaching structured programming  Ada  Developed under the sponsorship of the U.S.

Department of Defense (DOD) during the 1970s and early 1980s  Able to perform multitasking

1.8 History of C

 C   Evolved by Ritchie from two previous programming languages, BCPL and B in Bell Lab.

Used to develop UNIX  Used to write modern operating systems   Hardware independent (portable) By late 1970's C had evolved to "Traditional C“    Many of todays leading operating systems are written in C and/or C++.

C is mostly hardware independent.

With careful design, it’s possible to write C programs that are portable to most computers. 33  Standardization    Many slight variations of C existed, and were incompatible Committee formed to create a "unambiguous, machine-independent" definition Standard created in 1989, updated in 1999

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C++

• • C++ – Superset of C developed by Bjarne Stroustrup at Bell Lab.

– It has its roots in C, providing a number of features that i mproved C, and provides object-oriented capabilities – Dominant language in industry and academia Learning C++ – Because C++ includes C, some feel it is best to master C, then learn C++ – Starting in Chapter 18, we begin our introduction to C++

C++

 More important, it provides capabilities for object oriented programming .

 Objects are essentially reusable software components that model items in the real world.

 Using a modular, object-oriented design and implementation approach can make software development groups more productive.

 [Note: The programs in this book will run with little or no modification on most current C systems, including Microsoft Windows-based systems, Linux system, and more.]  Check out C Resource Center at

www.deitel.com/C

to locate “getting started” tutorials for popular C compilers and development environments. ©1992-2010 by Pearson Education, Inc. All Rights Reserved.

 C systems generally consist of several parts:  a program development environment,  the language and  the C Standard Library.

 C programs typically go through six phases to be executed.

 These are: edit , preprocess , compile , link , load and execute .

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Six Different Phase for Executing C program

   Phase 1 consists of

editing

This is accomplished with an editor program .

Two editors widely used on Linux systems are and emacs .

a file.

vi  Software packages for the C/C++ integrated program development environments such as Eclipse and Microsoft Visual Studio have editors that are integrated into the programming environment.

 You type a C program with the editor, make corrections if necessary, then store the program on a secondary storage device such as a hard disk.

 C program file names should end with the .c

extension.

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Six Different Phase for Executing C program

 In Phase 2, you give the command to compile program.

the  The compiler translates the C program into machine language-code (also referred to as object code ).

 In a C system, a preprocessor program executes automatically before the compiler’s translation phase begins.

 It indicate that certain manipulations are to be performed on the program before compilation.

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Six Different Phase for Executing C program

 These manipulations usually consist of including other files in the file to be compiled and performing various text replacements.

 In Phase 3, the compiler translates the C program into machine-language code.

 A syntax error occurs when the compiler cannot recognize a statement because it violates the rules of the language.

 Syntax errors are also called compile errors , or compile-time errors .

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Six Different Phase for Executing C program

• • • The next phase is called linking .

C programs typically contain references to functions defined elsewhere, such as in the standard libraries or in the private libraries of groups of programmers working on a particular project.

A linker links the object code with the code for the missing functions to produce an executable image (with no missing pieces).

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Six Different Phase for Executing C program

 The fifth phase is called loading .

 Before a program can be executed, the program must first be placed in memory.

 This is done by the loader , which takes the executable image from disk and transfers it to memory.

 Additional components from shared libraries that support the program are also loaded.

 Finally, the computer, under the control of its CPU, executes the program one instruction at a time.

©1992-2010 by Pearson Education, Inc. All Rights Reserved.

©1992-2010 by Pearson Education, Inc. All Rights Reserved.

Problems That May Occur at Execution Time

 Programs do not always work on the first try.

 Each of the preceding phases can fail because of various errors that we’ll discuss.

 For example, an executing program might attempt to divide by zero (an illegal operation on computers just as in arithmetic).

 This would cause the computer to display an error message.

 You would then return to the edit phase, make the necessary corrections and proceed through the remaining phases again to determine that the corrections work properly.

©1992-2010 by Pearson Education, Inc. All Rights Reserved.

 You may have heard that C is a portable language and that programs written in C can run on many different computers.

©1992-2010 by Pearson Education, Inc. All Rights Reserved.

 C is a rich language, and there are some part that are not obvious in the language and some advanced subjects we have not covered.

 For additional technical details on C, read the C Standard document itself or the book by Kernighan and Ritchie (

The C Programming Language, Second Edition).

©1992-2010 by Pearson Education, Inc. All Rights Reserved.

C Standard Library

 As you’ll learn in Chapter 5, C programs consist of pieces called functions .

 You can program all the functions you need to form a C program, but most C programmers take advantage of the rich collection of existing functions called the C Standard Library .

 Avoid reinventing the wheel.

 Instead, use existing pieces—this is called software reuse .

C Standard Library (Cont.)

 When programming in C you’ll typically use the following building blocks:  C Standard Library functions  Functions you create yourself  Functions other people (whom you trust) have created and made available to you

C Standard Library (Cont.)

 The advantage of creating your own functions is that you’ll know exactly how they work. You’ll be able to examine the C code.  The disadvantage is the time-consuming effort that goes into designing, developing and debugging new functions.