1. Introduction to Programming
Engineering 1020
Introduction to Programming
Peter King
Winter 2010

2. ENGI 1020: Variables Functions have two main components
Data – blocks of information
Numbers, letters
Instructions – task to be completed on the data
Mathematical, logical, display
Takes data and generates new data
Variables are the means we use to store data

3. ENGI 1020: Variables Variables offer a place to hold data
Data in a variable can change
You might say they're variable
Variables can hold data from a specified set of values (its type)
Variables must be declared before they can be used

4. ENGI 1020: Variables Type Variables are like bins for storing data
Different data goes in different bins
Big data, big bins
Small data, small bins
Int
… -3, -2, -1, 0, 1, 2, 3, .....
Computer places limit on max/min
Long
Same as int, but longer (bigger bin)

5. ENGI 1020: Variables Float Double Char -3.2111, 0.198734, 5.6, 7.0
Real numbers
Computer places limit on max/min
Double
Sames as float, but double the precision
More decimal places
Limited by computer
Char
All symbols that can be printed to screen
Letter, numbers, punctuation
Special chars (\n, \t)

6. ENGI 1020: Variables
CHAR_BIT Number of bits for a char object (byte) 8
INT_MIN Minimum value for an object of type int
INT_MAX Maximum value for an object of type int
UINT_MAX Maximum value for an object of type unsigned int
LONG_MIN Minimum value for an object of type long int
LONG_MAX Maximum value for an object of type long int
ULONG_MAX Maximum value for an object of type unsigned long int

7. ENGI 1020: Variables Variables have 4 attributes Name Address Type
Given by the human
Address
Assigned by the compiler
Type
Chosen by the human
Value
Set by human, computer, function, expression, etc.
The power of variables is that the value changes, but the name, type, address stay the same

8. ENGI 1020: Variables We must declare variables before use
Type name = expression
The type is chosen for the particular application
The name follows the rules and makes sense
The expression sets the initial value
Not required, but a good idea.
The computer will assign a new variable an address
The compiler keeps track of what address the variable points to
char c;
int x = 0;
double y = ;

9. ENGI 1020: Variables
bins

10. ENGI 1020: Variables
Examples from online notes