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Introduction to Computing

Introduction to Computing. In Today’s world…. Computers are indispensable They are more complex than ever before. What is a computer?. A machine which solves problems for people written in the form of programs What is a program?

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Introduction to Computing

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  1. Introduction to Computing

  2. In Today’s world… • Computers are indispensable • They are more complex than ever before

  3. What is a computer? • A machine which solves problems for people written in the form of programs • What is a program? - A sequence of instructions telling the computer what to do. • What is an Instruction? - Can be in Assembly language, Machine Language or High level Language.

  4. HARDWARE • Computer Organization • Computer consists of: - CPU(Central processing Unit) - Main Memory - I/O devices - Bus

  5. Computer Organization • CPU (processor) – brain of the computer. It’s function is to execute programs stored in Main memory by fetching them, examining them and executing them • CPU consists of: - Control Unit (Instruction fetch) - Arithmetic Logic Unit (Calculations) - Registers (high speed memory units)

  6. Computer Organization…contd. • How are instructions processed? • The control Unit: - fetches the instruction and decodes it, and sends control signals to the other units - Arithmetic Logic Unit performs calculations on the data

  7. Memory • What is memory? • A place for storing data and programs. • There are 3 types of memory: - Internal (within CPU..like registers) - Primary (fats..RAM) - Secondary (slow, but large capacity..Disk)

  8. I/O Devices • What is an I/O device? • Purpose is to transfer information between CPU and outside world • Egs. Keyboard, mouse, printer

  9. BUS • What is a BUS? • A set of parallel wires that can carry several bits at a time. • It carries instructions, data, address or command • 3 types: Data Bus, Address Bus, Control Bus.

  10. SOFTWARE • What is Software? • A set of programs. • In the earlier days, programs were written in 0’s and 1’s. (machine language, or Low Level Programming) • Disadvantage: Very cumbersome, and debugging becomes a problem.

  11. SOFTWARE..contd. • Remedy? • Using mnemonics. This was called Assembly Language Programming (ALP) • E.g. MOV AX, BX • But this needed a translator to convert AL to ML. This translator was called Assembler.

  12. SOFTWARE..contd. • Disadvantage of AL and ML? • They were not portable. I.e., once written, they were good only for that machine. Machine Specific. • Remedy? • Develop a language that is machine independent, and has more powerful features to suit specific needs .

  13. SOFTWARE..contd. • High Level Languages • These have the following features: • Machine Independence • Very good debugging facility • Good documentation • 1 instruction in a HLL corresponds to several in ALL or LLL

  14. SOFTWARE..contd. • High Level Languages meet specific needs such as business, scientific etc. • HLL’s come with their own translators, known as Compilers or Interpreters, and other software called Linkers, Loaders, Debuggers and Libraries. • Compilers convert the source code to object code, which is in machine language.

  15. SOFTWARE..contd. • How are HLL programs executed? • Compiler/Interpretor translates the source code. • The Loader, which is software, loads the object code into main memory. • The Linker links external files used by the current file.

  16. SOFTWARE..contd. • The editor, compiler, library, linker, loader, debugger can be integrated into one environment called the IDE, or Integrated Development Environment. MS Visual Studio is an e.g. • Compiler/Interpreter translates the source code. • The Library is a catalogue of predefined, compiled and tested functions. These contain geometric , arithmetic and other commonly used functions. • Users can build their own library functions.

  17. SOFTWARE..contd. • Programs are broadly divided into 2 categories: • Systems programs, which direct the internal operations of the computer. • E.g. Linker, Loader, Compiler • Applications Program, which solve user-oriented problems • E.g. payroll software, banking software.

  18. Introduction to Programming • Developing the simplest programs require the following steps: • Start->Problem Identification->Task Analysis-> Data analysis-> Deciding I/O-> developing algorithms->Coding->Testing-> Debugging-> Result

  19. Introduction to Programming • The algorithm phase is very important. • What is an algorithm? • A set of explicit, clear finite steps to obtain the desired output in finite time. • It is developed to produce the most efficient approach to solve a problem. • Efficient in terms of speed and memory usage. • Coding is implementing an algorithm in the programming language syntax.

  20. Intro. to Programming..contd. • The goal of programming is to develop programs that are clear, efficient and robust.

  21. HLL’s..C and C++ • C and C++ are entirely different languages. • Syntactically similar • But approach to programming in C++ is very different from C. • C++ is considered the language of the future.

  22. Object Oriented Programs • Pascal, BASIC, C, Fortran are all called Procedural languages. • This is because a program is a whole list of instructions telling the computer what to do. • What happens, when a program is very large? • List of instructions become unwieldy • Comprehension becomes tough • Unmanageable code.

  23. Object Oriented Programs • Remedy? • These problems led to development of structured programming. • Here a program is split into small functions, which is more manageable and readable. • This idea was extended to group a similar set of functions into what are called modules.

  24. Object Oriented Programs • Problems with structured programming: • Data Undervalued • Action on data is given more importance than the data itself. • This leads to inconsistencies among especially global data, which is accessed by many functions, giving undesired outputs at times.

  25. Object Oriented Programs • Remedy? • We need to hide data, or restrict it’s access to certain functions alone. • Other problems: • Non-oop languages allow users to use only built in data types. • What if the user wants to invent his own?

  26. Object Oriented Programs • This led to development of the object oriented approach. • Fundamental idea is to combine data and functions into 1 unit called OBJECT. • Here, the functions in an object only have access to the data within the object. • No external function s allowed access to that data. • Data encapsulation is born. Data and functions are encapsulated in an object.

  27. Object Oriented Programs • Data Hiding is achieved, by restricting access to data only to the member functions (or functions within an object.) • Analogy: • Corporate structure Vs. Object Oriented Design.

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