Program structure

Top down Step wise Refinement

• Start with the initial problem statement (Abstract form)
• Break the initial statement into few general steps
• Take each "step", and break it further into more detailed steps
• Continue the refinement process until you get a pretty specific, pseudo code which can be easily implemented 
• Write a Pseudo code of an algorithm outputs minimum of two numbers given by the user using Top down Step wise Refinement method.

Program Control Structures 

• Specify the next statement to be executed 
• Sequential Structures
• Selection Structures
• IF statement -Single selection

• IF ELSE statement -Double selection

• Nested IF ELSE 

• Switch Statement 

Repetition Structures

• Repeat a given statement , while some condition remains true
• Counter Controlled repetition
• Uses a variable counter to control the number of iterations
• Definite repetition : the number of iterations is known before the loop begin execution 
• Sentinel Controlled repetition
• Uses a sentinel value (a signal value, a dummy value or a flag value) to control the number of iterations 
• Indefinite repetition : the number of iterations is not known in advance how many times the loop will be executed

While Structure ( While Loop )

• Test the terminating condition at the beginning of the loop
• Loop body may not be executed at all
• Write a program to print the all the integer numbers from 10 to 1

For Structure (For Loop)

• Used when the number of iterations is known in advance

Do-While Structure

• Test the terminating condition at the end of the loop
• The statement of block of statements in the loop will be executed at least once

Infinite Loop

• Loop which never end 
• A while loop without increment or decrement statement 
• A while loop with a terminating condition which always evaluates as TRUE