Overview of Computer Systems and C Programming

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Overview of Computer Systems and C Programming

• Week 1
• Department of Computer Science
• Faculty of Science and Technology
• Assumption University

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Agenda

• Course Organization (Course Outline)
• Overview of computer systems, instruction, and
  data storage (Slides)
• Computer programs, programming languages, and
  software engineering (Slides)
• Programming Demonstration
• Creating your first C program (Hello World)
• Understanding C program structure
• Understanding Dev-C IDE

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Computer Systems
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Anatomy of a Computer
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Computer Components

• Central Processing Unit
• Main Memory
• Input and Output
• System Interconnection

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Central Processing Unit

• A component in a digital computer capable of
  executing a program
• Interpret computer program instructions and
  processes data
• Components of a CPU
• Control Unit (CU)
• Arithmetic Logic Unit (ALU)

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Primary Storage (Main Memory)

• Main memory is the only one directly accessible
  to the CPU.
• CPU continuously reads instructions stored there
  and executes them.
• Any data actively operated on is also stored
  there in uniform manner.

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Memory Organization
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Memory Size

• Bit (Binary Digit) is the smallest unit of memory
  which can store a 0 or a 1.
• Byte contains 8 bits.
• Kilobyte (KB) 1,024 bytes (210)
• Megabyte (MB) 1,048,576 bytes (220)
• Gigabyte (GB) 1,073,741,824 bytes (230)
• Terabyte (TB) 1,099,511,627,776 bytes (240)

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Secondary Storage

• Secondary storage differs from primary storage in
  that it is not directly accessible by the CPU.
• The computer usually uses its input/output
  channels to access secondary storage and
  transfers desired data using intermediate area in
  primary storage.
• Secondary storage does not loose the data when
  device is powered down (non-volatile).

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Input/Output Devices

• Input device is a hardware mechanism that
  transforms information in the external world into
  the computer.
• Output device is any piece of computer hardware
  equipment used to communicate the results of data
  processing carried out by an information
  processing system (such as a computer) to the
  outside world.

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Bus System

• An information highway or bus system connects the
  components of the system
• Address Bus carries the address of the memory
  location or I/O device being accessed.
• Data Bus carries the data signals.
• Control Bus carries the control signals between
  the CPU and the other components of the system

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Computer Programs
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Program

• Program is a series of instructions stored in the
  main memory that are executed sequentially by the
  processor.
• Program is written by a programmer using program
  language.
• The program of a computer system is called its
  software and includes
• System software
• Application software

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Algorithm

• Algorithm is a finite list of well-defined
  instructions for accomplishing some task that,
  given an initial state, will proceed through a
  well-defined series of successive states,
  eventually terminating in an end-state.

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Programming Languages

• Programming language is an artificial language
  that can be used to control the behavior of a
  machine.
• Programming languages, like natural languages,
  are defined by syntactic and semantic rules which
  describe their structure and meaning
  respectively.
• Syntax are the rules of a language that describe
  how the words of that language are to be
  arranged.
• Semantic is the study of meaning in
  communication.
• Two major classes of programming languages
• Low-level languages
• High-level languages

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Low-Level Programming Language

• Low-level programming language is a language that
  provides little or no abstraction from a
  computer's microprocessor.
• There are basically two types of low-level
  programming language
• Machine language
• Assembly language

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High-Level Programming Language

• High-level programming language is a programming
  language that are more abstract, easier to use,
  or more portable across platforms
• Such languages often abstract CPU operations such
  as memory access models and management of scope
• Examples of high-level programming languages
  include Fortran, Cobol, Pascal, C, C, Java

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Compilers

• Compiler is a computer program (or set of
  programs) that translates text written in a
  computer language (the source language) into
  another computer language (the target language).
• The original sequence is usually called the
  source code and the output called object code.

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C Compilers

• C is a general-purpose programming language
  with high-level and low-level capabilities.
• C is a statically typed, free-form,
  multi-paradigm, usually compiled language
  supporting procedural programming, data
  abstraction, object-oriented programming, and
  generic programming.
• C is regarded as a mid-level language. This
  indicates that C comprises a combination of
  both high-level and low-level language features.

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Stages in Programming

• Problem specification define what the solution
  should accomplish.
• Solution design define the process that can be
  used to achieve the desired result.
• Implementation translate an algorithm into
  working commands or instructions (code).
• Documentation describe what the program should
  accomplish and explain how various segments of
  the code are designed.
• Testing and debugging ensure a computer program
  produces a correct result for many sets of input.

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Software Engineering

• Software engineering is the application of a
  systematic, disciplined, quantifiable approach to
  the development, operation, and maintenance of
  software
• The goals of software design are to ensure that
  software is
• Reliable
• Easy to write
• Easy to understand and use
• Easy to upgrade

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Software Engineering

• Techniques for achieving software engineering
  goals
• Abstraction and top-down design no coding can
  begin until a sufficient level of detail has been
  reached in the design of the system
• Reuse of well-tested code save development time
• Modularity subdivide a larger object into
  smaller pieces that are self-contained and
  self-standing
• Information hiding allow safe use of a device
  without requiring that the users understand the
  inner working of that device

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Mechanics of Writing Programs

• Editing Writing a program
• Compiling Translating from C into machine
  language
• Linking Combining your program with other
  libraries
• Running Letting the computer execute a program
• Debugging Running step by step through a program
  searching for mistakes