-Short introduction to C

You maybe don't know or probably didn't think about this but you are using program preprocessing before compiling it. As I said before compiling I mean, that each time you are compiling your project, C compiler prepares program file to be ready for compilation. Preprocessor includes other files to main file, defines symbol constants and macros, prepares conditional compilation of code. All preprocessor tasks are marked with ampersand symbol “#”. Lets go through most of directives of preprocessor:
#include

This is similar to #define preprocessor where you can describe a set of constatnts. Using preprocessor we use:

#define zero 0

#define one 1

#define two 3

But there is an alternative of using enumerating using keyword enum:

enum (zero=0,one, two); //zero=0, one=1; two=2

By default enumeration assigns values from 0 and up.

Now you can use enumeration like in following example:

Basically Structures are nothing more than collection of variables so called members. Structures allows to reference all members by single name. Variables within a structure doesn't have to be the same type. General structure declaration:

struct structure_tag_name{

	type member1;

	type member2;

	...

	type memberX

};

or

struct structure_tag_name{

	type member1;

	type member2;

	...

	type memberX

} structure_variable_name;

The main thing what microcontrollers does is operates with data. There are four main operations that microcontrollers does: adds, abstracts, multiplies and divides (+,-,*,/). division can be split in division “/” and modulus operation “%”. For instance i1/i2 is integer division.

Other part of operators is Relation operators. They are used for boolean conditions and expressions. Expressions with these operators return true or false values. Zero is taken as false and non zero value as true. Operators may be as follows: <, <=, > >=, ==, !=.

The priority of the first four operators is higher than that of the later two operators. These operators are used in relational expressions such as:

What are variables in C language. Variables are simple keywords which are defined by the values. Values can be changed. Variables are like a boxes with some size where values like apples can be put in. So variables can be various forms and sizes so called variable types.

Variable type is defined by a reserved word which indicates the type and size of variable identifier:

unsigned char my_char;

long int all_my_numbers;

int number;

Why do we need variables? The basic answer is that memory is limited and compiler needs to know much space to reserve for each variable. So the programmer needs to specify the variable type and its size by using one of reserved words from the table: