CMPSC 201 - Ch. 1 Notes

Objective #1: Explain the differences between low-level languages and high-level ones ranging from Assembly to C/C++ to Basic.

• Low-level languages
  • use commands and keywords that are difficult for a layman to understand. Often the commands are not full words and they are brief.
  • use many individual instructions or statements to perform a task.
  • run more quickly though since their instructions can be "translated" easier by the hardware of the computer.
  • can precisely control the hardware (chips, peripherals, etc.)
  • The classic example of a low-level computer language is Assembly.
    
    
• High-level languages
  • easier for a layman or novice to read and understand since they use full English words and even phrases to perform instructions.
  • Complicated tasks can sometimes be performed by one command or statement.
  • Run more slowly since some the instructions, statements, etc. have to be "translated" into low-level languages (such as Assembly) before they are actually understood by the hardware.
  • more portable to different computing platforms since one language can be fine-tuned ("translated") to work with different types of hardware
  • BASIC, Pascal, FORTRAN are always considered high-level. C & C++ are usually considered to be high-level but some people classify them as being more low-level than other high-level languages.

Objective #2: Explain the differences between interpreted languages and compiled ones. C++ is usually compiled, while Basic is usually interpreted.

• Interpreted languages run more slowly because statements and instructions are interpreted by an interpreter line by line. If a run-time or syntax error is found, it immediately stops the execution of the program.
• Compiled languages run more quickly because a program is first compiled by a compiler. The compiler checks for syntax and other errors during this stage. The compiler also creates an object file (.obj extension for Visual C++). Then, one must build the project which links the object file to necessary ancillary files such as header files and an executable file is created. The executable file can then be used independently without need of the compiler or linker.
• The executable version of a compiled program will run more quickly than an interpreted program. For interpreted languages, the interpreter does not produce a standalone, executable file.

Objective #3: Explain the differences between procedural programming and object-oriented programming (OOP).

• C, FORTRAN, BASIC, and many other languages are used in a procedural programming paradigm. A program usually consists of sets of statements which perform tasks. The tasks are performed sequentially and when necessary they process data that is stored separately.
• Object-oriented programming (OOP) became popular in the early 1980's however it had been proposed and conceptualized as early as the 1960's. Programs usually consist of sets of statements but the cornerstone of an object-oriented program are classes and objects. Classes provide the structure and function for objects. An object "knows" how to perform tasks because of the functionality that its class entails. An object also holds its own structured data. Therefore, in an object-oriented program, objects interact with each other allowing more efficiency and flexibility. In a procedural program, tasks must be explicitly detailed and, to a degree, all data must be stored beforehand in a an ordered manner.

Objective #4: List a number of common, popular languages.

• FORTRAN, BASIC, COBOL, Pascal, C, C++
• Microsoft's Visual Basic is a popular version of the BASIC language. Visual Basic is object-based rather than strictly procedural like traditional versions of BASIC. The next version of Visual Basic (v 7) will supposedly be object-oriented.

Objective #5: List and explain each of the Programming Process.

• The 5 steps of the Programming Process are:
  
  
  1. Define the problem and understand the given specifications. Create a test plan.
  2. Develop an algorithm by writing pseudocode.
  3. Code the program by writing it out on paper first.
  4. Test and debug the program.
  5. Document and maintain the program.
     
     
• Note that the Bronson textbook considers the 3 steps of the Software Development Procedure to be the following. They are comparable to the 5 steps of the Programming Process. You will be expected to list and describe the 5 steps of the Programming Process and not Bronson's.

1. Development & Design
2. Documentation
3. Maintenance
   
   Within the Development & Design step, the following steps are detailed:
   
   
   1. Analyze the Problem
      1. What to do?
      2. What are the expected outputs?
      3. What inputs will I have?
   2. Develop the Solution
   3. Code the Solution
   4. Test & Correct the Solution
      

Objective #6: List and explain different examples of documentation.

• program description - This will consist of a few sentences in a comment at the beginning of programming assignments submitted for this course. However in industry this section of the program could be very lengthy (i.e. many pages.)
• algorithm development & changes - This section of documentation also precedes the actual code. When programmers edit a program, they include a few lines (or more) detailing the changes that they made so that other future programmers can see what changes were made to the original implementation.
• program listing (inline comments) - These comments should be placed along the right margin beside the actual code if possible. They annotate the actual code which could be confusing to other programmers.
• sample test runs - This kind of documentation shows others how the program will run and interact with the user. It can also be viewed as a partial test plan.
• user's manual - This documentation is usually printed and exists apart from the source code. It is often called external documentation.
  
  
• You will be expected to include a program description, inline comments within the programs that you complete for this course. Please realize though that software written in industry includes much more documentation as outlined above & in our textbook.

Objective #7: List and explain the four basic types of statements: sequence, selection (if), iteration (loops), & invocation (functions).

• Sequence statements are simply statements that naturally follow one another from the top of the program to the bottom. For example, in the "hello world" program all of the statements are sequence statements.
  
  
• Selection statements include if statements and switch statements that we will learn later in this course. Selection statements are sometimes called conditional or decision statements. An example of a selection statement is "If I scored a 60 or higher, then I passed the course; otherwise, I failed." There are really two possible end results of this statement. Therefore, both paths are not followed. You cannot pass the course and fail the course at the same time. (We will study these kinds of statements in a later chapter.) In C++, this if statement might look like this:
  
  

if (score >= 60)
{
   cout << "I passed" << endl;
}
else
{
   cout << "I failed" << endl;
}

• Iteration statements allow the compiler to return to a point higher in the program in order to continuously repeat one or more statements. (We will study these kinds of statements in a later chapter.) In C++, this is an example of a do loop that prints "hello world" ten times:
  

while (num < 10)
{
   cout << "hello world" << endl;
   num = num + 1;
}

• Invocation statements allow you to place statements that you wish to use several times during a program in one section (usually at the bottom of your program) and then call those statements whenever repeatedly without having to retype them in the program. (We will study these kinds of statements in a later chapter.) In C++, we use functions like this:

  void displayHelloWorld()
  {
     cout << "hello world" << endl;
  }

• A good exercise would be to pretend that you are a robot and that each day you simply follow a set of instructions. Write out everything that you do as a simple instruction. Each instruction is one of the types of statements above.
  
  Example:
  
  Listen to alarm.
  If I am really tired, hit the snooze button; otherwise, get out of bed.
  Walk to bathroom.
  If cap is on toothpaste, take it off.
  Pick up toothbrush.
  Squeeze toothpaste on toothbrush.
  etc.
  
• Corrado Böhm and Giuseppe Jacopini proved that a combination of sequence, selection, & iteration statements are sufficient to express essentially all programs.
  

Objective #8: Explain the importance of a test plan and the importance of developing it before developing and coding the solution.

• It is absolutely necessary to create a test plan early in the Programming Process otherwise you may overlook certain program inputs.
  
  
• In fact, it is helpful to have a different person, team, or department to create a test plan so that the programmer who designs the algorithm and code is "unbiased" by the test plan that has been created.
  
  
• You should include test plan items for:
  
  
  • reasonable inputs
  • boundary cases
  • invalid inputs - This kind of test plan item will not be required on the test plans submitted with programming assignments in this CMPSC 201 course.

Objective #9: Explain the differences between using pseudocode and flowcharts to developing a program's algorithm.

• pseudocode, see p. 21 of Bronson
• flowcharts, see pp. 12 & 21 of Bronson
• We will use pseudocode rather than flowcharts in this course.