MUFIX Community Session Name : Introduction To Programming Speaker : Islam El-Hosary Term 1 (2009-2010)

1. Introduction to
Programming
“How to win friends
and influence computers”

4. A Brief History of Computers
General purpose minions
Orders
Human calculators
Mechanical calculators
Electronic calculators
General purpose machines
Programs

5. What Is Programming
Programming is just telling a computer to do
something,
BUT
Computers know very little and have no common
sense what-so-ever, so your instructions have to
be broken down to small, simple parts,
AND
Computers will do exactly what you tell them.

7. Basic Programming
Programming at it’s core is about two things:
defining problems, and solving problems.
These two aspects are tightly integrated
• To solve a problem you first must clearly know
what it is
• Clearly and completely defining a problem
gets you a long ways towards a solution

9. Four Tools To Get Started
Just getting started is often the hardest part of
the project. Before diving in to the code, do
the design document. Four tools to help are
–Action/Event List
–Flow Chart
–Data Model
–Iterative Refinement

10. Action List
This is a good tool to use in applications that have
user interaction.
Write down each action the user can take.
Add a bit of detail info to each action
• Circumstances in which the user may take the
action (1-3 sentences, and/or list)
• What happens when they do the action (1-3
sentences)
• What other actions this one allows and denies
(list format)

11. Flow Charts
Flow charts are a very useful tool to clarify and
define programming problems
• They delineate key points in your program
• They’re especially good for state-based
programs, such as web applications
Don’t get too bogged down in details when
creating a flow chart – stay high level

12. Data Model
A data model is a detailed description of the
information that the application will
manipulate.
Start with a general idea/concept, then break it
down into smaller parts, and repeat.
Aim for having each part be a string, a number,
or a list or collection thereof.

13. Iterative Refinement - the Ur-Program
The process of iterative refinement
2. Say what you want the computer to do
3. If it’s all in terms the computer will understand,
then stop, you’re done
4. Otherwise, break each part into simpler steps
5. Go to step 2
NOTE: works for small children as well as computers

14. The Real World
These are important concepts, and when done right
you end up documenting your code as you go.
HOWEVER…
Real-world programming often doesn’t explicitly
involve these techniques except at high levels in the
design document. You should definitely use them
there, and for actual coding keep them in mind as
fallback strategies if your stuck on a problem.

15. What Computers Can Do Well

16. What Computers Can Do Well
Doing the same things over and over
Remembering things
Mathematics, ‘regular’ and true / false
Changing actions based on conditions
Taking in information
Sending out information

17. What Computers Can Do Well
Doing the same things over and and Subroutines
Loops over
Remembering things Variables and Assignment
Mathematics, ‘regular’ and true / falseOperators
Statements
Changing actions based on conditions
Conditionals
and Blocks
Taking in information
Sending out information
Input
Output

18. Statements, and Blocks
A statement is a basic instruction for the computer
Statements are executed in order, from first to last
One or more statements may be grouped together
into a block
A block is marked by curly braces
{ and }

19. Loops
A loop is a special kind of statement that tells a computer
to repeat a given set of instructions
A for-loop repeats a given number of times
e.g. say “hi” five times:
for (1..5) { say “hi” }
A while-loop repeats as long as a certain condition is true
e.g. go somewhere :
while (not arrived) { take step }

20. Subroutines
A subroutine, function or procedure is a block of statements
that’s been given a name and which is executed when ever
that name is used. Essentially, it’s a miniature sub-program
that you can use in your larger program.
Once a function finishes, the execution returns to the place
from which it was called.
Functions can take parameters, or arguments, which allow
values to be sent into the block of code
Functions can return values.

21. Variables
A variable has a name, or identifier, and may have a
value associated.
Associate a given value with a given variable by making
an assignment.
Variables can be declared, which creates them without
any value. Some languages require this.

22. Variable Names
MUST:
Start with a letter
Contain letters or numbers or underscores
SHOULD:
Be meaningful (often 10+ characters)
Be readable (use _ or mixCase to mark words)
Follow convention (start lower case, i, x, y)

23. Basic Values
Literal values:
Numbers
0, -3, 8.223419783
Strings (a series of characters)
“zero”, ”0”, “cheddar cheese”
Expressions:
One or more values, expressions, or variables combined by operators
8.3 * 4.291
2
“smoked” . “ “ . “cheddar”
A variable used in a expression is replaced by its value
ingredient_count + 3

24. Operators
There are all the standard math operators
+ - * / % ()
The string concatenation operator combines two or more strings into
one
Depends on the language (often . or +)
There are many other operators too
Boolean math
Comparisons
Specialized
Operators combine values and expressions into larger expressions

25. Conditionals
A conditional, or branch, statement executes a
block of other statements based on whether a
given condition is true or false
Conditions are evaluated using boolean
operators, as well as comparisons and other
things that are true or false

26. General Conditional Statement
if (condition)
Block executed if condition is true
else if (other condition)
Block executed if other condition is true
else
Block executed if all conditions are false

27. Input and Output
Special statements get data into and out of a
program.
Details vary by language
Data can come from:
keyboard, web page, mouse, file, other
Data can go to:
screen, file, the internet, other

28. Comments
Comments are a way to put text in the program
code which does not get executed. This is very
useful for leaving notes / descriptions /
explanations, and for testing.
Comments are usually denoted by
# or // to comment to the end of the line
/* to comment out multiple lines
*/

29. Best Practices
Always make backups of original working code before
messing with it
Use comments to mark what you change, how, and
when, and to keep copies of original statements
Test early, test often
Work together – more eyes means fewer bugs
Read the manual – there are great references online
Look at examples

34. mr.islamelhosary@gmail.com