C-Programming

Basics

computers are very dumb machines
- they only do what they are told to do
the basic operations of a computer will form what is known as the computer's instruction set
to solve a problem using a computer, you must provide a solution to the problem by sending instructions to the instruction set
- a computer programs sends the instructions necessary to solve a specific problem
the approach or method that is used to solve the problem is known as an algorithm
- so, if we were to create a program that tests if a number is odd or even
  - the statements that solve the problem becomes the program
  - the method this is used to test if the number is even or odd is the algorithm
to write a program, you need to write instructions necessary to implement the algorithm
- these instructions would be expressed in the statements of a particular computer language, such as Java, C++, Objective-C, or C

CPU (center processing unit)
- does most of the computing work
- Instructions are executed here
RAM (random access memory)
- stores the data of program while it is running
hard drive (permanent storage)
- Store files that contain program source code, even while the computer is turned off
Operating system
- developed to help make it more convenient to use computers
- a program that controls the entire operation of a computer
  - all input and output
  - manages the computer's resources and handles the execution of programs
  - windows, unix, Android, etc
fetch / execute cycle (life of a cpu)
- fetches an instruction from memory(using registers) and executes it (loop)
- A gigahertz CPU can do this about a billion times a second

High-level programming languages make it easier to write programs
- opposite of assembly language
- C is a higher level programming language that describe actions in a more abstract form
- the instructions(statements) of a program look more like problem-solving steps
- do not have to worry about the precise steps a particular CPU would have to take to accomplish a particular task
  - total = x +vs. mv ax, 5, mv cs 4, etc...
compilers
- a program that translates the high-level language source code into the detailed set of machine language instructions the computer requires
- the program does the high-level thinking and the compiler generates the tedious instructions to the cpu
compilers will also check that your program has valid syntax for the programming language that you are compiling
- find errors and it reports them to you and doesn't produce an executable until you fix them
higher-level languages are easier to learn and much easier to program in than are machine languages

define the program objectives
- understand the requirements of the program
- get a clear idea of what you want the program to accomplish
design
- 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 implement, translate the design in syntax of C
- you need to use a text editor to create what is called a source code file
compile
- translate the source code 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
- just because a program is running, does not mean it works as intended
- need to test, to see that your program does what it is supposed to do(may find bugs)
  - debugging is process of finding and fixing program errors
  - making mistakes is a natural part of learning
maintain and modify the program
- programs are released and used by many people
- have to continue to fix new bugs or add new features