1. Brief Version of Starting Out with C++ Chapter 1 Introduction to Computers and Programming

2. Contents 1.1 Why Program? 1.2 Computer Systems: Hardware and Software 1.3 Programs and Programming Languages 1.4 What Is a Program Made of? 1.5 Input, Processing, and Output 1.6 The Programming Process 1.7 Procedural and Object-Oriented Programming

3. 1.1 Why Program? Computer – programmable machine designed to follow instructions Program – instructions in computer memory to make it do something Programmer – person who writes instructions (programs) to make computer perform a task SO, without programmers, no programs; without programs, computer cannot do anything

4. 1.2 Computer Systems: Hardware and Software Main Hardware Component Categories: 1. Central Processing Unit (CPU) 2. Main Memory 3. Secondary Memory / Storage 4. Input Devices 5. Output Devices

5. Main Hardware Component Categories Input Device Central Processing Unit Main Memory Output Device Secondary Storage Devices

6. Central Processing Unit (CPU) Comprised of: Control Unit Retrieves and decodes program instructions Coordinates activities of all other parts of computer Arithmetic & Logic Unit Hardware optimized for high-speed numeric calculation Hardware designed for true/false, yes/no decisions

7. Main Memory Volatile – erased when program terminates or computer is turned off Also called Random Access Memory (RAM) Organized as follows:  bit: smallest piece of memory. Has values 0 (off, false) or 1 (on, true)  byte: 8 consecutive bits. Bytes have addresses.

8. Secondary Storage Non-volatile: data retained when program is not running or computer is turned off Comes in a variety of media:  magnetic: floppy disk, zip disk, hard drive  optical: CD-ROM

9. Input Devices Used to send information to computer from outside Many devices can provide input:  Keyboard, mouse, scanner, camera  Disk drives

10. Output Devices Used for information sent from a computer program Many devices can be used for output:  Computer monitor and printer

11. Software – Programs That Run on a Computer Categories of software:  Operating system: programs that manage the computer hardware and the programs that run on them. Ex: Windows, UNIX, Linux  Application software: programs that provide services to the user. Ex: word processing, games, programs to solve specific problems

12. 1.3 Programs and Programming Languages Program: a set of instructions to a computer to perform a task Programming Language: a language used to write programs

13. Programs and Programming Languages Types of languages:  Low-level: used for communication with computer hardware directly. Often written in binary machine code (0’s/1’s) directly.  High-level: closer to human language

14. From a High-level Program to an Executable File a) Create file containing the program with a text editor. b) Run preprocessor to convert source file directives to source code program statements. c) Run compiler to convert source program into machine instructions. d) Run linker to connect hardware-specific code to machine instructions, producing an executable file. - Steps b–d are often performed by a single command or button click. - Errors detected at any step will prevent execution of following steps.

15. From a High-level Program to an Executable File Source Code Preprocessor Modified Source Code Compiler Object Code Linker Executable Code

16. 1.4 What Is a Program Made Of? Common elements in programming languages:  Key Words  Programmer-Defined Symbols  Operators  Punctuation  Syntax

17. Example Program #include using namespace std; int main() { string name; cout << "What is your name? "; cin >> name; cout << "Hello there, " << name; return 0; }

18. Key Words Also known as reserved words Have a special meaning in C++ Can not be used for another purpose Examples in program: using, namespace, int, main

19. Programmer-Defined Symbols Names made up by the programmer Not part of the C++ language Used to represent various things: variables (memory locations), functions, etc. Example in program: name

20. Operators Used to perform operations on data Many types of operators:  Arithmetic - ex: +,-,*,/  Assignment – ex: = Examples in program: > << stream insertion operator >> stream extraction operator

21. Punctuation Characters that mark the end of a statement, or that separate items in a list Examples in program: ;

22. Syntax The rules of grammar that must be followed when writing a program Controls the use of key words, operators, programmer-defined symbols, and punctuation

23. 1.5 Input, Processing, and Output Three steps many programs perform: 1) Gather input data: - from keyboard - from files on disk drives 2) Process the input data 3) Display the results as output: - send it to the screen - write to a file

24. 1.6 The Programming Process 1. Define the purpose of the program 2. Visualize the running program; sketch the user interface 3. Model the program using design tools 4. Check the model for errors 5. Enter the program into the computer and compile it

25. The Programming Process 6. Correct errors and recompile until there are none 7. Execute (run) the program 8. Correct execution errors, recompile, rerun 9. Validate results: does the output meet what was defined in step 1?

26. 1.7 Procedural and Object-Oriented Programming Procedural programming: focus is on the process. Procedures/functions are written to process data. Object-Oriented programming: focus is on objects, which contain data and the means to manipulate the data. Messages sent to objects to perform operations.

27. Integrated Development Environment (IDE).net Appendix F. Visual C++.net Appendix K and M. Turbo C++ V4.5 at BCC ***** no need to use Using namespace std; SIMPLE But with a “PRICE” !!! Dev (your compiler)

28. The #include directive #include For this slide and the following slides refer to slide 17

29. C++ uses namespace to organize different names used in programs. Avoids the need for putting std:: before every reference to cout or cin so we can use just cout in our code. Every name used in the iostream library is part of a namespace called std, that is why every cout object is really called std :: cout Using namespace std;

30. The Main Function. A function is a group of related statements (instructions) which together perform a particular task. int main( ) main is the name of the function. int. a type of data that will be returned indicating the correct execution of the function from the last statement return 0; void main(), another option without the need for return 0; not supported by the Dev Compiler

31. The Function Body All related statements that belong to a function are included within the body of the function. All statements are included within a set of Curly braces { }

32. cin and cout Data stream flows either input (cin >>) or output cout << The << is called insertion operator. (it inserts the output to the output device (monitor) The >> is called extraction operator. (concerns the input stream).

33. Return 0; Tells the OS that the program ended normally. Examples in JCL (SOC 007)

34. Where does your input come from? Built in (assignment statements). From the keyboard (using cin, getline …) From a file.( using an input file)

35. Where does your output go to? To the monitor (the screen). To a printer. To an output file.

36. Errors Syntax: a violation of the rules of the programming language  Caught by the compiler  Your program wont compile as long as they exist.  i.e. a variable not declared, or a typing error Runtime: Asking the system to perform an impossible operation  Could crash your program and or your compiler.  i.e. attempt to divide by 0. Logic: a result of a bad design or wrong coding  The program compiles, runs and produces an answer.  Hard to find  i.e Z = X / Y;  where the correct statement is Z = X * Y Warnings: may have no effect on the execution of the program. Declared but not ever used variable