• Computer

  - A programmable device that can store, retrieve, and process data

• Hardware

  - Actual circuits and associated machinery (physical components)
  - Keyboard, monitor, disk, tape, floppy drive, camera, microphone

• Software

  - Another name for a program or programs
  - systems software (operating system, editor, compiler) and applications software

• Program

  - The step-by-step instructions that tell the computer how to do its work
  - These instructions are in a language understood by the computer

• Programming language

  - A set of rules, symbols, and special words used to construct a program
  - C and C++ are languages understood by the computer

• How do we write a program (program's life cycle) ?

  - Problem-Solving Phase

  * Analysis and Specification
  * Develop an algorithm (a step-by-step procedure for solving the problem)
  * Verify the algorithm by following the steps exactly

  * Example: drive to the airport

       Get on I10
          if traffic heavy,
            Drive to Exit 18 
            Turn right on River Road
            Turn left at airport entrance
          else
            Drive to exit 23
            Turn left on River Road
            Turn right at airport entrance
          Search lot for parking space
  

  - Implementation phase

  * Translate the algorithm into a program (coding)
  * Test the program and correct possible errors (debugging)

  - Maintenance phase

  * Use the program
  * Maintain the program by modifying it to meet new requirements and correct new errors

• An algorithm can have many different implementations

  <Figure 1-2>
  

• Think first, code later !!!
  <Figure 1-3>
  

• Documentation

  - The comments that make a program easier for others to understand, use, and modify

• Information

  - Any knowledge that can be communicated

• Data

  - Information that can be put into a form a computer can use
  - Data are represented by 1s and 0s (binary form) in the memory of the computer
  - A single 1 or 0 is called bit
  - A group of 8 bits is called byte (2^8=256 combinations)
  - Each character (A,a,B,b,*,+,...) is usually represented by a byte inside the computer

Programming Languages

• Machine language

  - A language made up of binary-coded instructions, that is used directly by the computer
  - Different computers might represent the same instruction with different codes
  - The machine code for one computer is not the same as for another
  - Programs written in machine language are very difficult to read and modify

• Assembly language

  - Similar to machine language with the difference that instructions are in an easy-to-remember form
  - A program that translates an assembly language program into machine code (assembler) is needed

                Assembly language             Machine language
                   ADD                           100101   
                   SUB                           010011
  

• High-level programming languages

  - Easier to use than assembly or machine languages because they are closer to English
  - C, C++, Pascal, Fortran, Cobol, Ada are all high-level languages
  - A program (compiler) translates programs written in a high-level language (source program) into machine language (object program)

• Portability

  - A benefit of high-level languages is that the allow the programmer to write machine independent (portable) code
  - Programs written in assembly or machine languages are not portable from one computer to another
  <Figure 1-5>
  

• Compilation vs Execution

  - During compilation, the computer translates the source program to an object program
  - During execution, the object program is loaded into the computer's memory and the computer executes (runs) each instruction of the object program
  <Figure 1-6>
  

• Fundamental structuring statements (instructions)

  - Sequence: a series of statements that are executed one after another
  - Selection: different statements are executed depending on certain conditions
  - Loop: instructions are repeated while certain conditions are met
  - subprogram: break a program into smaller units

  <Figure 1-7>
  

Computer Organization

• Loosely defined as in the following figure:

  <Figure 1-8>
  

• Input device

  - Eyes and ears of the computer
  - Used to receive informations from the outside world
  - Connects to different -peripheral- devices (keyboard, mouse, video camera etc.)

• Output device

  - Tongue/mouth, hands, and legs of a computer
  - Used to communicate information, or to do something
  - Monitor screen, printer, robotic arm

• CPU or Central Processing Unit

  - Brain of the computer
  - Talks to every other unit via the nervous system (buses or wires)
  - Responsible for the behavior of every other unit in the system

• ALU or Arithmetic/Logic Unit

  - Specialized part of the brain that is good at math and at making very simple decisions
  - Generally referred to as a co-processor

• Control Unit

  - Specialized part of the brain that controls the actions of the other units so That the instructions (program) are executed in the correct sequence

• Memory

  - Used by the CPU to keep instructions and data during the execution of a program
  - Organized as an ordered sequence of storage cells, each of which can hold a piece of data
  Each memory cell has a distinct address which is used to store and retrieve information
  - CPU picks up an instruction from memory and acts on it
  - Also known as RAM or Random Access Memory

  <Figure from page 53 and Figure 1-9>
  

• Auxiliary storage device

  - Long term storage for programs that are not in active use at the time
  - Also used to keep data that needs to be stored for long term
  - Magnetic tape drives, disk drives, CD-ROM drives, etc.

• System Software

  - Operating system: a collection of programs that control and allocate resources in a computer system - both in hardware and software
  - Editor: an interactive program used to create and modify source programs or data

Four Kinds of Computers

• Mainframes

  - Very large (they can fill a room) and very fast
  - Used by big companies (insurance companies, airlines companies etc.)
  - Many users

• Microcomputers or Personal Computers (PCs)

  - Small computers that can fit on top of a desk
  - Usually one user

• Minicomputers

  - Intermediate-sized computers (workstations)
  - Less expensive than mainframes and more powerful than personal computers
  - Used mostly by research institutions
  - One or more users

• Supercomputers

  - Tremendous processing power (Deep Blue vs Kasparov !!!)
  - Include many CPUs
  - Used mostly for research

History of C++

• BCPL (Basic Combined Programming Language), 1967

  - Designed by Martin Richards in 1967
  - Useful for writing system software like compilers and operating systems

• B

  - Developed by Ken Thompson for early versions of UNIX
  - Inspired by BCPL

• C

  - Developed by Dennis Richie (AT&T Bell Labs) in 1972

• C++

  - Developed by Bjarne Stroustrup (Bell Labs) in 1985

  - It is a superset of C

Problem-Solving Techniques: Some Hints

• You need three things to solve a problem

  - A clear statement of the problem
  - The necessary input
  - The required output

• Ask questions
  - Try to understand the problem by asking questions

• Look for things that are familiar

  - Do not reinvent the wheel !!!

  <Figure 1-12>
  

• Solve by analogy

  - Draw an analogy between the problem you are trying to solve and other problems
  - Do not limit yourself to computer-oriented solutions
  - Having a broad experience will make you a good programmer

  <Figure 1-13>
  

• Divide and Conquer

  - Break up large problems into smaller units that are easier to solve

  <Figure 1-15>