MSAS5104 Programming with Data Structures and Algorithms

1. MSAS5104Programming with Data Structures and Algorithms Week 3 Scott Marino Scott Marino MSMIS Kean University

2. Computer languages What is a program? Modular design The programming process The C++ language Values in C++ Variables in C++ Creating a program Compiling a program Lab 1 / Homework Topics Scott Marino MSMIS Kean University

3. Computer Languages • First generation language • Each CPU has a fixed set of instructions hard-coded into it in a language known as machine language • The only language the computer truly understands • The only instructions the computer can execute • Consists of a series of “offs” and “ons” • A single instruction to a computer such as - display a character on the screen may require dozens of instructions in machine language • Nobody programs in machine language Scott Marino MSMIS Kean University

4. Computer Languages • Second generation language • Assembly languages are one step removed from the machine languages • The programming logic behind assembly language is much the same as machine language • The actual machine code language is translated to characters • Machine language = 0011011011 • Assembly Language = ADD Scott Marino MSMIS Kean University

5. Computer Languages • Second generation language • A program called an “assembler” translates the assembly language program into machine code • Assembly languages are written to mimic the computers machine language • Usually provides the most efficient programs because it is written with the same logic as machine language • Development time is slower because of the detailed instructions required to perform a task Scott Marino MSMIS Kean University

6. Computer Languages • Third and Fourth generation languages • Designed for humans to work with • English-like syntax • A single 3GL command can translate to dozens of machine code instructions • C, C++, COBOL, JAVA, Pascal, Perl, etc. • Despite being English-like, strict syntax is required to write a program that can be translated properly Scott Marino MSMIS Kean University

7. What is a program? • To us, a program is simply a set of textual instructions, saved as a file • Many steps are required to translate the textual program into a form that the computer can use • Different languages all undergo a similar process for creating executable programs • For this class, we will focus on C++ Scott Marino MSMIS Kean University

8. What is a program? • The process of creating an executable program • Starts with creating a set of instructions in a programmable language • The set of instructions is saved as a text file known as “source code” • A program known as a compiler is invoked to translate the source code to “object code” • The compile step will produce an object module or return the syntax errors encountered Scott Marino MSMIS Kean University

9. What is a program? • A program known as a linker is invoked to add “system modules” to the object module • I/O routines and other required pre-written code • Each executable program is typically linked on the computer in which it will execute • Sometimes it can be linked on a similar machine and “ported” to other machines • Testing is required of the program • Just because it compiles and links does not mean it is doing what it was intended to do Scott Marino MSMIS Kean University

10. What is a program? • From the 1940’s to the mid-1990’s, most program creation was done as individual tasks • Write program, save it, invoke compiler, invoke linker • Separate debugging and testing tools • In the mid-1990’s, integrated development environments began to emerge as PC’s became more common • In a single environment, you can write a program, click the save icon, and click to compile and link • Integrated debugging and testing tools Scott Marino MSMIS Kean University

11. Modular Design • Many programming tasks are quite large in scope • MS-Windows, Word, Excel, Accounting, games, etc • Consists of many thousands of lines of code • Take a complex task and break it into smaller pieces known as modules • Combine to individual modules to create the final program • Step-wise refinement • Break each task down into increasingly smaller sizes Scott Marino MSMIS Kean University

12. Modular Design • A trend has been towards object-oriented programming • Treat everything as an object • Determine the properties (attributes) for the object • Define the behaviors (methods) for the object • Create a published/public interface • Encapsulate (hide) the details of the code from view • Abstract - we know how to use the objects, but don’t care how they do what the do • Objects are written to be re-usable Scott Marino MSMIS Kean University

13. The programming process • Creating a program is a balance of several factors in the business environment • Execution efficiency • Will it run fast enough? • Programming efficiency • Will it take too long to write? • Maintainability • Can it be easily updated to accommodate change? • Code re-use • Is there any code already written that can be re-used? Scott Marino MSMIS Kean University

14. The programming process • Task • Investigate the situation • Analysis • Research the problem and create a plan to solve it • Design • Develop the procedure to solve the problem • Implementation • Write the actual code • Test Scott Marino MSMIS Kean University

15. The C++ language • 1967 - BCPL (Basic Combined Programming Language) commonly referred to as B • 1972 - Dennis Ritchie improves B and calls it C • 1983 - C is enhanced and C++ is created as the next generation of C • The ++ operator in C is “increment by 1” • There are ANSI (American National Standards Institute) standards written for C, but there are none for C++ Scott Marino MSMIS Kean University

16. The C++ language • C++ was designed to be a modular language • The C++ compiler is flexible with spacing, blank lines, and indentation, however, it is desirable to write programs that are neat, organized, and well documented • Program source code should follow an outline format with each level or subordinate topic being indented for readability Scott Marino MSMIS Kean University

17. C++ Anatomy • Comments • Comments are used in a program to explain the purpose of a command or function or to document other important details of the program • The “//” operator is used to denote the start of comments • Each comment line ends with the first carriage return • The /* …comments … */ is operators are used to create blocks of comments • Can span multiple lines or be used on a single line Scott Marino MSMIS Kean University

18. C++ Anatomy • Directives • Directives are instructions to the compiler to perform certain actions • In C++ each directive starts with the “#” (pound) sign • #include <iostream> • Directives can add common modules to a program or can perform conditional compilation Scott Marino MSMIS Kean University

19. C++ Anatomy • Statements • Statements in C++ are code that, when compiled, perform specific actions • test_grade = 99; // assign 99 to test_grade • All statements end with a “;” (semicolon) • Statements can span more than one line • Quoted data cannot span multiple lines Scott Marino MSMIS Kean University

20. C++ Anatomy • Objects • C++ has a limited number of statements, but has a large number of objects • Objects have behaviors and properties • cout << “printing something\n”; • cout is an object • the << is the insertion operator • the quoted data prints • the \n is a new line character • the line ends with a semicolon Scott Marino MSMIS Kean University

21. C++ Anatomy • Functions • A function is a set of instructions that performs a single operation • Functions can include statements, objects, references to other functions, machine language, and other “stuff” • Functions are used to create “modular” code Scott Marino MSMIS Kean University

22. C++ Anatomy • Functions • int main(void){… some code …} • Every C++ program must contain only one “main” function • Program execution begins with the main function and executes all code within the curly braces Scott Marino MSMIS Kean University

23. C++ Anatomy • Declarations • Variables and functions must be “declared” before you can use them in a program • int test_grade; • Declares a variable named test_grade • Header files included into a program contain declarations for common functions and are typically self contained • They include declarations for all the variables they require • The cout function is declared in the “iostream” header Scott Marino MSMIS Kean University

24. Values in C++ • Numeric values • There are real numbers and integer numbers • Real numbers contain decimal points • Integers are whole numbers • Sometimes referred to as the counting numbers • Can be negative or positive Scott Marino MSMIS Kean University

25. Values in C++ • Character values • By enclosing a value in single quotes ‘4‘, you tell the C++ compiler to refer to the ASCII value for the data inside the quotes • All character references MUST be enclosed in single quotes • A numeric 4 is different than a character ‘4’ • C++ allows funny things to happen when mixed data types are used in a single statement Scott Marino MSMIS Kean University

26. Special Characters Generally not printable on the screen and cannot be typed \0 -- null value \a -- audible (bell) \b -- backspace \f -- form feed \n -- new line \r -- carriage return \t -- horizontal tab \v -- vertical tab \? -- print question mark \\ -- print backslash Values in C++ Scott Marino MSMIS Kean University

27. Values in C++ • String • A string is a set of values enclosed within “double quotes” • “Escape” special characters inside of strings by using the backslash • question marks, carriage returns, etc. • Keep in mind, string values have slightly different properties and methods than character and numeric data Scott Marino MSMIS Kean University

28. A simple program • The Hello World example • #include <iostream>using namespace std; // for some compilersint main(void) // main program function { cout << “Hello World!\n”; return 0; // end program with 0 return code} Scott Marino MSMIS Kean University

29. A simple program • Telnet to eve.kean.edu • Some basic UNIX required • Using “pico”, create a file called hello.cpp containing the hello world program • Compile the program • Execute the program Scott Marino MSMIS Kean University

30. Connecting to Kean • Run PuTTY • Configure a session to connect to eve.kean.edu • Connect as “ssh” which connects to port 22 Scott Marino MSMIS Kean University

31. Introduction to Unix • mv Move or Rename a file • cp Copy a file • rm remove or delete a file • ls -rtl list directory contents • mkdir make a directory • cd change directory • passwd change your password • exit close the session / logoff Scott Marino MSMIS Kean University

32. PICO Edit • From the command line enter “pico file.name” • Use arrow keys to navigate around the screen • Backspace and delete keys can be used to correct typing mistakes • Ctrl-O will save your file • Ctrl-X will exit the editor • Search the web for tutorials for using PICO Scott Marino MSMIS Kean University

33. Compiling a program • In UNIX • g++ -oprogramprogram.cpp • invokes the UNIX C/C++ compiler • -oprogram tells the compiler to create the executable program as “program” • program.cpp is the file name for the source program • Make sure not to create the executable program with the exact same name as the source program Scott Marino MSMIS Kean University

34. Executing a program • From the command line type “program” • This will execute the program Scott Marino MSMIS Kean University

35. Tips and tricks • Open 2 UNIX sessions one for editing and one for compiling • Save the program (Ctrl-O) on one session and toggle to the other to compile • Avoid creating each program from scratch • Copy an existing program to the new name • Pick an identifiable name for your programs • Create a directory for each program • KISS - Keep it simple Scott Marino MSMIS Kean University

36. Printing the results • Cut/Paste the results into notepad or other text editor • Highlight the text in putty to put it into the windows clipboard • Toggle to the editor and click paste • Format as courier or a fixed width font for easier viewing • Print Scott Marino MSMIS Kean University

37. Homework / Lab 1 • Write a program to print the following: • Your Name • Phone Number • City, State Zip • Must have all the punctuation, end of lines, formatting, etc. • Program comments must include: • // Student name and e-mail// Assignment N// Date// Description of program Scott Marino MSMIS Kean University

38. Homework / Lab 1 • Turn in • Program source code • Execution results • Write down the compiler used Scott Marino MSMIS Kean University