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  1. 1. Chapter 1: Introduction In this chapter you will learn about: Overview of PC components The different types of language Natural Language Formal Language Functional / Imperative Language Programming Languages C as an imperative language C program at a glancePrinciples of Programming - NI July 2005 1
  2. 2. Computer Hardware Components Components of a PCPrinciples of Programming - NI July 2005 2
  3. 3. Input / Output Devices Input Devices Accepts information from the user and transforms it to digital codes that the computer can process Example: keyboard, mouse, scanner Output Devices An interface by which the computer conveys the output to the user Example: monitor, printerPrinciples of Programming - NI July 2005 3
  4. 4. Main Memory A semiconductor device which stores the information necessary for a program to run. 2 types ROM (Read Only Memory) Contains information that is necessary for the computer to boot up The information stays there permanently even when the computer is turned off. RAM (Random Access Memory) Contains instruction or data needed for a program to run Got erased when the computer is turned off.Principles of Programming - NI July 2005 4
  5. 5. Central Processing Unit (CPU) Does most of the work in executing a program The CPU inside a PC is usually the microprocessor 3 main parts: Control Unit Fetch instructions from main memory and put them in the instruction register ALU (Arithmetic Logic Unit) Execute arithmetic operations Registers Temporarily store instructions or data fetched from memoryPrinciples of Programming - NI July 2005 5
  6. 6. Storage Devices A magnetic device used to store a large amount of information. Store the software components or data needed for the computer to execute its tasks. Could be “read only” or “writable”. Example: Hard drive, CD ROM, floppy disksPrinciples of Programming - NI July 2005 6
  7. 7. Network Devices Connect a computer to the other computers. Enable the users to access data or execute programs remotely. Example: modem, Ethernet cardPrinciples of Programming - NI July 2005 7
  8. 8. Natural language Our everyday-language; spoken and written Not 100% needed to understand: “Do you want to buy this computer ?” remains comprehensible Depends on circumstances; the context: “Do you like one ?” doesnt make sense on its own. It needs a situation around it: – someone holding a bouquet of flowers: you might take one – someone pointing to an expensive car: your opinion is asked – someone offers you an oily cloth to sneeze: you dont take itPrinciples of Programming - NI July 2005 8
  9. 9. Semantics and Syntax Semantics – the meaning of the language within a given context Syntax - Syntax are the rules to join words together in forming a correct expression or phrase. In natural languages it is often possible to assemble a sentence in more than one correct ways.Principles of Programming - NI July 2005 9
  10. 10. Formal Language Language with limited, defined, words Each concatenation of words (phrase) has a single, clearly defined meaning no (miss-)interpretation possible Sometimes called “Context Free Language” To talk to a computer; to instruct a computer; our commands must be 100% clear and correct. Often there is only a single, correct syntax.Principles of Programming - NI July 2005 10
  11. 11. Functional / Imperative Language Functional Language: Tell what to do, but not how: sum [1...10] Imperative Language: Tell what to do, but mainly how: “Take number 1 and add the next number to it; then add the next number to the sum; and so on; until you have reached 10 as number to be added. Then print the sum of all numbers”Principles of Programming - NI July 2005 11
  12. 12. What is Programming? Programming is instructing a computer to do something for you with the help of a programming language The two roles of a programming language: Technical: It instructs the computer to perform tasks. Conceptual: It is a framework within which we organize our ideas about things and processes. In programming, we deal with two kind of things: Data - representing objects we want to manipulate Procedures -descriptions or rules that define how to manipulate data.Principles of Programming - NI July 2005 12
  13. 13. Programming Language Formal Language used to communicate to a computer. A programming language contains instructions for the computer to perform a specific action or a specific task: Calculate the sum of the numbers from 1 to 10‘ Print “I like programming”‘ Output the current timePrinciples of Programming - NI July 2005 13
  14. 14. Programming Language Can be classified into as a special-purpose and general-purpose programming languages. Special-purpose : is design for a particular type of application Structured Query Language (SQL) General-purpose : can be used to obtain solutions for many types of problems Machine Languages Assembly Languages High-Level LanguagesPrinciples of Programming - NI July 2005 14
  15. 15. Machine Language The only language that the processor actually understands‘ Consists of binary codes: 0 and 1 Example: 00010101 11010001 01001100 Each of the lines above corresponds to a specific task to be done by the processor. Programming in machine code is difficult and slow since it is difficult to memorize all the instructions. Mistakes can happen very easily. Processor and Architecture dependentPrinciples of Programming - NI July 2005 15
  16. 16. Assembly Language Enables machine code to be represented in words and numbers. Example of a program in assembler language: LOAD A, 9999 LOAD B, 8282 SUB B MOV C, A LOAD C, #0002 DIV A, C STORE A, 7002 Easier to understand and memorize (called Mnemonics), compared to machine code but still quite difficult to use. Processor and Architecture dependentPrinciples of Programming - NI July 2005 16
  17. 17. High-Level Language Use more English words. They try to resemble English sentences. Therefore, it is easier to program in these languages. The programming structure is problem oriented - does not need to know how the computer actually executes the instructions. Processor independent - the same code can be run on different processors. Examples: Basic, Fortran, Pascal, Cobol, C, C++, Java A high level language needs to be analyzed by the compiler and then compiled into machine code so that it can be executed by the processor.Principles of Programming - NI July 2005 17
  18. 18. C Programming LanguageWhy C ? Because based on B; developed at Bell Laboratories Developed by Dennis Ritchie at Bell Laboratories in the 1960s In cooperation with Ken Thomson it was used for Unix systems The C Language was only vaguely defined, not standardized, so that almost everyone had his own perception of it, to such an extend that an urgent need for a standard code was creeping upPrinciples of Programming - NI July 2005 18
  19. 19. C Programming Language cont… In 1983, the American National Standards Institute (ANSI) set up X3J11, a Technical Committee to draft a proposal for the ANSI standard, which was approved in 1989 and referred to as the ANSI/ISO 9899 : 1990 or simply the ANSI C, which is now the global standard for C. This standard was updated in 1999; but there is no compiler yetPrinciples of Programming - NI July 2005 19
  20. 20. C – An Imperative Language C is a highly imperative language We must tell it exactly how to do what; the means and functions to use; which libraries to use; when to add a new line; when an instruction is finished; in short: everything and anything… Hint: Observe the syntax in the next slidePrinciples of Programming - NI July 2005 20
  21. 21. A Simple Program in C #include <stdio.h> main() { printf("I like programming in C.n"); }Principles of Programming - NI July 2005 21
  22. 22. A Simple Program in C - explanation #include <stdio.h> standard Library, input-output, header-file Begin of program main() { Start of Segment Function for printing text printf("I like programming in C.n"); Insert a new line } End of statement End of SegmentPrinciples of Programming - NI July 2005 22
  23. 23. C Output I like programming in C.Principles of Programming - NI July 2005 23
  24. 24. Summary We have looked at some underlying hardware We have seen some different types of languages; the relevance of semantics and syntax. We have observed the detail necessary in an imperative language to instruct a computer properly. Finally, we examined the syntax to print a line of text to the screen of our computer.Principles of Programming - NI July 2005 24