Study Notes #5

IDE – Integrated Development Environment

Algorithm – approach or method used to solve a problem

• If we are to create a program that tests if a number is odd or even:
  • The statements that solve the problem become the program
  • The method that is used to test if the number is odd or even is the algorithm
  • To write a program, you need to write the instructions necessary to implement the algorithm. These instructions would be express in the statements of a particular computer language, such as Java, C++, Objective-C or C

Program – the statements that solve a problem

• A computer is a machine that does what was told. A program tells the computer what to do. The algorithm is the process behind a program that tells the computer what to do. A programmer maps, designs, and creates the program.

Computer’s Instruction Set – formed by basic operations

1. To solve a problem using a computer, you must provide a solution to the problem by sending instructions to the instruction set.
2. A computer program sends the instructions necessary to solve a specific problem.

Higher Level Programming Languages – make it easier to write programs

Compilers

• a program that translates the high-level language source code into the detailed set of machine language instructions the computer requires
• does the high-level thinking and the compiler generates the tedious instructions to the cpu
• will check that your program has valid syntax for the programming language that you are compiling
• finds errors and reports them to you and doesn’t produce an executable until you fix them

Writing C Program

1. Define the program objectives
   • Understand the requirements, you have to get a clear idea of what you want the program to accomplish
2. Design the program
   • Decide how the program will meet the above requirements
   • What should the user interface be like
   • How should the program be organized
3. Write the code
   • Start implementation, translate the design in the syntax of C
   • Use a text editor to create what is called a source code file
4. Compile
   • translate the source into machine code (executable code)
   • consists of detailed instructions to the CPU expressed in a numeric code
5. Run the program
   • the executable file is a program you can run
6. Test and Debug
   • debugging – finding and fixing program errors
7. Maintain and modify the program
   • after the release, have to continue to fix new bugs or add new features

Develop the habit of planning before coding.
Work in small steps and constantly test.

---

C

• a general-purpose, imperative computer programming language that supports structured programming
• uses statements that change a program’s state, focuses on how
• one of the most widely used programming languages of all time
• reliable and readable program
• used on everything
• preferred language for producing word processing programs, spreadsheets, and compilers
• popular for programming embedded systems
• continues to play a strong role in the development of Linux
• easy to modify and adapt to new models or languages
• C is a subset of C++ with object-oriented programming tools added

Features

• produces compact and efficient programs
• one of the most important programming languages and will continue to be so
• portable
• programmer-oriented
• pointers play a big role in C
  • direct access to memory
  • supports efficient use of pointers

Disadvantages

• use of pointers is problematic and abused
• you can make programming errors that are difficult to trace
• there is opportunity to write obscure code

kernel – the brain of operating system

Four Fundamentals Tasks in the Creation of any C Program

1. Editing – the process of creating and modifying your C source code
   • source code is inside a file and contains the program instructions you write
   • choose a wise name for your base file name (all source files end in the .c extension)
   • we will use an IDE (code blocks) for this class, but you can use any editor to create your source code
2. Compiling
   • a compiler converts your source code into machine language and detects and reports errors in your code
   • the input to the compiler is the file you produce during your editing (source file)
   • Two-Stage Process
     1. Preprocessing phase – code may be modified or added to
     2. Actual compilation that generates the object code
   • the standard command to copile your C programs will be cc (or the GNU compiler, which is .gcc)
     • cc -c myprog.c or gcc -c myprog.c
     • if you omit the -c flag, your program will automatically be linked as well
3. Linking
   • the purpose of the linking phase is to get the program into a final form for execution on the computer
   • linking usually occurs automatically when compiling depending on what system you are on, but, can sometimes be a separate command
   • success fill produce and executable file
     • Windows .exe
     • UNIX/Linux a.out
4. Executing

syntactic error - expression that has unbalanced parentheses

semantic error - use of a variable that is not defined