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
To solve a problem using a computer, you must provide a solution to the problem by sending instructions to the instruction set.
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
Define the program objectives
Understand the requirements, you have to get a clear idea of what you want the program to accomplish
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
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
Compile
translate the source into machine code (executable code)
consists of detailed instructions to the CPU expressed in a numeric code
Run the program
the executable file is a program you can run
Test and Debug
debugging - finding and fixing program errors
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
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
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
Preprocessing phase - code may be modified or added to
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
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
Executing
syntactic error - expression that has unbalanced parentheses
semantic error - use of a variable that is not defined</code></pre>
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