Controle structures - Part I

What is program?

Procedure
Sequence of steps that should be performed.
Well designed program consists of smaller independent parts.
These independent parts should be executed in some order.

What is control structure?

Control structure defines in which order program is going to be executed.
First do this, then do this, after do that…
If some condition is met, do this. Otherwise do that.

Controle structure types

Sequence logic, or sequential flow
Selection logic, or conditional flow
Iteration logic, or repetitive flow

How is program executed?

Top to bottom

Sequence logic - Sequence flow

Sequence of steps that should be executed

Selection logic - Conditional flow

If statement
If-else statement
Switch - does not exist in python. Can be replicated by else-if statement.

Iteration logic - Repetitive flow

For loop
While loop
Do loop - does not exist in python. Can be made using for or while statement.

Controle structure

Every control structure consists of two parts:
- Head
- Body
How are head and body separated?
Can there be more than one head/body?
Head and body are separated by colon and indentation.
There can be more than one head/body.If-else statement.
Head
- Contains sth that evaluates to boolean
Body
- Contains set of instructions that should be performed if head evaluates to true

Break, continue, pass

Break: stop loop cycle when condition is met
Continue: just continue execution of program to next interation. Code after 'continue' keyword will be ignored
Pass: Do sth when condition is met, but code after 'pass' keyword will not be ignored