Chapter 1 Introduction to Computers and C++ Programming

Introduction A program is a step-by-step series of instructions for a computer Programming is the process of writing these instructions Programmers, or developers, design and write programs using a programming language or development tool C++ is a programming language that provides the structure for efficient and economical programs

Programming a Computer Companies need developers to build general application software packages Custom applications are built for specific needs Existing programs need maintenance and upgrades New applications will be needed due to emerging technologies

Programmers follow a general methodology called the program development cycle to structure the development process. The phases of the cycle are Analyze the requirements Design the solution Validate the design Implement the design Test the solution Document the solution

Phase 1 – Analyze Requirements Verify that the requirements are clear and complete Evaluate the problem to determine that it is solvable using a program List the required input and output data Determine whether the input data is available for testing

Phase 1 – Analyze Requirements Ensure that a solution, or algorithm, can be developed with the information provided in the requirements Verify the user interface specifications

Phase 2 – Design Solution Develop a logical model that illustrates the sequence of steps you will take to solve the problem Use design tools such as storyboards, object structure diagrams, flowcharts, and pseudocode to outline the logic of the program An algorithm is a sequence of precise instructions that leads to a solution  Example: Determine how many times a name occurs in a list of names

Example: Determine how many times a name occurs in a list of names

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Example: Determine how many times a name occurs in a list of names 1. Get list of names 2. Get search name 3. Establish counter, set to zero 4. For each name in list: 1. Compare name in list to search name 2. If list name = search name, increment counter by one 5. Answer is the number indicated by the counter

Phase 2 – Design Solution Storyboards are sketches of the user interface

Phase 2 – Design Solution Flowcharts graphically represent the logic used to develop an algorithm Control structures allow the programmer to specify the code that will execute only if a condition is met Flowcharts use pseudocode, English, or mathematical notation inside symbols to represent the steps of a solution

Phase 2 – Design Solution Pseudocode is an English representation of how the program code should be written

Phase 3 – Validate Design The programmer steps through the solution with test data The user agrees that the program design solves the problem put forth in the requirements The user verifies that the initial requirements document contains all necessary requirements

Phase 4 – Implement Design Write the code that translates the design into a program Create the user interface Create comments within the code that explains the purpose of the code Test the code as it is written Test related code

Phase 4 – Implement Design

Phase 5 – Test Solution Create a test plan with test cases of sample input data and expected output Perform integration testing to ensure that components interact correctly Test boundary values Document any problems  If results are unsatisfactory, a new iteration of the development cycle begins

Phase 6 – Document Solution Requirements documents, program design documents, user interface documents, and documentation of the code Test cases and proof of successful completion of testing Program code should be archived electronically

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Object-Oriented Programming and Design Object-oriented programming  Data and the code that operates on the data are packaged into a single unit called an object Object-oriented design  Identifies how objects interact with each other to solve a problem

Objects Class  Implementation of an object or set of objects with a common structure and behavior Class diagram  A tool displaying a hierarchy of classes, including superclasses and subclasses Instance  A specific occurrence of an object Attributes  The properties of an individual object Method/function  The code of an operation on the data of an object

Operations Message  The activation of an operation through naming the object and the operation to be performed on the object Trigger  Impetus for a sent message Event  The process of a trigger sending a message that results in an operation

Event Diagrams and UML Graphically represents relationships among event and operations Useful for designing event-driven programs

Encapsulation The process of hiding the implementation details of an object from its user The user is shielded from the system’s complexity Information hiding provides access to an object only through its messages Objects can be modified without requiring application modification

Inheritance An efficient way to reuse code by defining a subclass as an extension of another class The subclass inherits all the data and functions of the superclass The subclass has at least one attribute or method that differs from its superclass

Polymorphism Allows an instruction to be given to an object using a generalized command The same command will obtain different results depending on the object receiving the command The specific actions internal to the object are encapsulated from the user

Abstraction Simplifies complex reality by modeling classes appropriate to the problem Works at most appropriate level of inheritance for a given aspect of the problem Abstraction is also achieved through composition (car)

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Computer Hardware Computer hardware are the physical components of the computer.

Input/Output Devices Input/Output devices provide communication between user and hardware.  Input Devices Keyboard Mouse Scanner  Output Devices Monitor Speakers Printer

Processors and Memory Central Processing Unit (CPU)  Performs basic functions, millions and billions of times per second (brains of the computer) Random-Access Memory  Stores data used by the CPU (before and after processing)

Data Storage Data storage uses a variety of media. Capacity is measured in bits and bytes:  A bit represents the on or off state of a transistor (symbolized by a 1 or a 0).  A byte is eight bits.  A kilobyte is 2 10 or 1,024 bytes.  A megabyte is 1,048,576 bytes.

Hard Drives The hard drive is the primary storage device in a computer. Hard drives are:  Long term, rewritable storage  Large capacity  Inexpensive  Fixed media (relatively difficult to move from one computer to another)

Removable Media Some storage devices are more portable:  CD/DVD Medium capacity Inexpensive Easy to transport from one computer to another  Flash, Zip, USB drives Differing capacities Differing price per MB

Computer Software Software can be divided into two categories:  Systems software includes operating systems, compilers, and utilities.  Application software runs on top of an operating system.

What is an operating system? An operating system (OS) manages the hardware and software on a computer system. An OS:  Manages memory and hardware resources  Allocates resources to applications  Provides a consistent interface for applications

Operating Systems UNIX/Linux  Multiuser OS  Multitasking  Runs on many types of hardware  Modular tools Mac OS  First mainstream graphical user interface  Icons (pictures) and mouse replaced command line interface DOS/Windows  DOS gained popularity with first PCs  Windows provided graphical interface to DOS  Windows later separated itself from DOS underpinnings

Low-Level Languages Low-level programming languages use simple commands to communicate with the CPU:  Machine language (most basic language of the CPU)  Assembly language (human readable, but close to machine language)

High-Level Languages High-level languages can be procedural or object-oriented:  Procedural languages use a step-by-step process to solve a problem. Basic, Pascal, C  Object-oriented languages model problems using objects that correspond to real-world counterparts. Smalltalk, C++, Java

Origins of C++ Derived from C, which was derived from B (short for BCPL), developed in AT&T Bell Laboratories Why ++? Early 1980’s Most of C is a subset of C++

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Parts of a Program User Programmer Variable Declarations Variables Integer Statements (executable statements) cin and cout /n Line breaks and spacing include directive int main() return statement Compiling and running a program – what does a compiler do? **Test program

Testing and Debugging bug debugging Kinds of Errors:  Syntax error – compile time error (this program won’t run at all) – you’ve broken a rule of the language  Semantic – compile time error – you’ve changed the meaning of some word in your code  Run-time error – program compiles fine, and initially runs, but at some point an error is thrown and the program stops running  Logic error – program compiles fine, runs fine (no error is thrown throughout execution of the program), BUT the program doesn’t behave as it was meant to  System – software isn’t installed correctly Error message vs. warning message