C programming language Computer Programming Language 計算機程式設計 Chapter 1 Overview 台大電機系 吳安宇教授 Sept. 2002

C programming language Introduction –We will learn the C programming language –Learn structured programming and proper programming techniques –Chapter 15 - Introduction to C++, a superset of C (more later) –This course is appropriate for –Technically oriented people with little or no programming experience –Experienced programmers who want a deep and rigorous treatment of the language

C programming language What is a Computer? Computer –Device capable of performing computations and making logical decisions –Computers process data under the control of sets of instructions called Computer programs Hardware –Various devices comprising of a computer –Keyboard, screen, mouse, printer, disks, CD-ROM, network cards, memory (DRAM and SRAM), and Central Processing Unit (CPU) Software –Programs that run on a computer

C programming language Computer Organization Six logical units in every computer: 1.Input unit Obtains information from input devices (keyboard, mouse) 2.Output unit Outputs information (to screen, to printer, to control other devices) 3.Memory unit Rapid access, low capacity, stores input information 4.Arithmetic and logic unit (ALU) Performs arithmetic calculations and logic decisions 5.Central processing unit (CPU) Supervises and coordinates the other sections of the computer 6.Secondary storage unit Cheap, long-term, high-capacity storage, stores inactive programs

C programming language Computer Organization (cont’d) BIOS: Basic Input/Output System, RAM: Random Access Memory

C programming language Computer Organization

C programming language Computer Performance Improvement

C programming language Computer Cost at Same Performance

C programming language Computer Evolution

C programming language Evolution of Operating Systems Operating systems (OS) –Boot, Command, Control all HW and SW –Manage Input and Output devices: User Interface –Manage transitions between jobs/tasks (memory allocation, CPU status) : Server for the user Batch processing –Do only one job or task at a time Multiprogramming/Multitasking –Many jobs or tasks sharing the computer resources (may for one single user) Timesharing –Runs a small portion of one user ’ s job then moves on to service the next user (for multiple users)

C programming language Computer Software and Hardware

C programming language Software Organization

C programming language Personal Computing, Distributed Computing, and Client/Server Computing Personal computers – Economical enough for individual Distributed computing –Computing distributed over networks Client/server computing –Sharing of information across computer networks between file servers (central program/database) and clients (personal computers)

C programming language Machine Languages, Assembly Languages, and High-level Languages Three types of programming languages 1.Machine languages –Strings of numbers giving machine specific instructions –Example: – (Binary number) – = (1437)_8 (Octal no.) – = 31F (Hexadecimal no.) 2. Assembly languages –English-like abbreviations representing elementary computer operations (translated via assemblers) –Example: LOAD BASEPAY = 31F machine lang. ADD OVERPAY STORE GROSSPAY

C programming language Machine Languages, Assembly Languages, and High-level Languages (II) 3. High-level languages –Similar to everyday English and use mathematical notations (translated via compilers) –Example (e.g., C language): grossPay = basePay + overTimePay

C programming language Mapping of -High-level Language ( e.g., C program) -Assembly Language (Computer Instruction Sets) -Machine Language for Computer execution (Binary code for logic circuits)

C programming language History of C C –Evolved by Ritchie of Bell Labs. from two previous programming languages, BCPL and B –Used to develop UNIX –Now, most operating systems written with C or C++ –Hardware independent (portable) –By late 1970's C had evolved to "Traditional C" Standardization –Many slight variations of C existed, and were in compatible –Committee formed to create a "unambiguous, machine- independent" definition -> portable language –Standard created in 1989, updated in 1999

C programming language The C Standard Library C programs consist of pieces/modules called functions –A programmer can create his own functions Advantage: the programmer knows exactly how it works Disadvantage: time consuming –Programmers will often use the C library functions Use these as building blocks –Avoid re-inventing the wheel If a premade function exists, generally best to use it rather than write your own Library functions carefully written, efficient, and portable

C programming language C++ and C++ How to Program C++ –Superset of C developed by Bjarne Stroustrup at Bell Labs –"Spruces up" C, and provides object-oriented capabilities Objects - reusable software components –Object-oriented design very powerful 10 to 100 fold increase in productivity –Popular language in industry and university –We will cover only part of C++ in this course

C programming language Structured Programming Structured programming –Disciplined approach to writing programs –Clear, easy to test and debug, and easy to modify –Avoid the use of GOTO statement Multitasking –Specifying that many activities run in parallel –Object-oriented programming

C programming language Basics of a Typical C Program Development Environment Phases of C/C++ Programs: 1.Edit 2.Preprocess 3.Compile 4.Link 5.Load 6.Execute Loader Primary Memory Program is created in the editor and stored on disk. Preprocessor program processes the code. Loader puts program in memory. CPU takes each instruction and executes it, possibly storing new data values as the program executes. Compiler Compiler creates object code and stores it on disk. Linker links the object code with the libraries, creates a.out and stores it on disk Editor Preprocessor Linker CPU Primary Memory Disk

C programming language Hardware Trends Every year or two the following approximately double: –Amount of memory in which to execute programs –Amount of secondary storage (such as disk storage) to hold programs and data over the longer term –Processor (CPU) speeds at which computers execute their programs

C programming language History of the Internet Initiated by Advanced Research Project Agency (ARPA): ARPAnet -> NSFnet -> Internet The Internet enables –Quick and easy communication via –International networking of computers Packet switching (c.f. Circuit switching) –Transfer digital data via small packets –Allows multiple users to send and receive data simultaneously No centralized control –If one part of the Internet fails, other parts can still operate

C programming language History of the World Wide Web World Wide Web –Based on Hypertext Markup Language (HTML) –Locate and view multimedia-based documents on almost any subject –Makes information instantly and conveniently accessible worldwide –Possible for individuals and small businesses to get worldwide exposure –Changing the way business is done

C programming language Focus of this Course A careful walkthrough of C language in this course –If you need additional technical details Read the C standard document Read the bible book by Kernigan and Ritchie (the 1 st C language book) –Focus on Program clarity Programs that are convoluted are difficult to read, understand, and modify Very important programming habit for yourself and others. –Programming concept can be applied to other languages: Matlab for engineering/science works.

C programming language How To Get C++ Compiler The textbook has included C++ compiler –Visual C++ –Borland C++ Builder –Turbo C++, etc. The suggested compiler is Turbo C 3.0 (MS- DOS version), which can be downloaded at