Types, Operators and Expressions
- Variables and constants are the basic data object manipulated in a program.
- Expressions combine variables and constants to produce new values.
- All variables must be declared before they are used, usually at the begining of the function before any executable statements.
- Variable names can made up of letters and digits.
- Traditional C practice is to use lower case for variable names, and all upper case for symbolic constants.
Data Types and Sizes
- char a single byte, capable of holding one character in the local character set.
- int an integer, typically reflecting the natural size of integers on the host machine.
- float single-precision floating point.
double double-precesion floating point.
- Constants are expressions with a fixed value
- The types :
- Defined constant
- Declared constant
- Literals are used to express particular values within the source code of a program.
- Example : r = 69
the 69 in this piece of code was a literal constant.
- Literal constants can be divided in Integer Numerals, Floating-Point Numerals, Characters, Strings and Boolean Values.
- We can define your own names for constants that you use very often without having to resort to memory consuming variables, simply by using the #define preprocessor directive
- The format :
#define identifier value
- Example :
#define Phi 1.618 #define pi 3.14159
- With the const prefix you can declare constants with a specific type in the smae way as you would do with a variable.
- Example :
const int damage = 666; const char tabulator = '\t';
- It will treated just like regular variables except that their values can’t be modified after their definition.