1. Introduction to Programming
Prof. George Zolla
Prof. Gary Porter (IS 2020) .

2. Programs
A program is a set of step-by-step instructions that directs the computer to do the tasks you want it to do and produce the results you want.

3. Programming Languages
A programming language is a set of rules that provides a way of telling a computer what operations to perform.

4. What Can a Program Do? A program can only instruct a computer to:
Read Input
Sequence
Calculate
Store data
Compare and branch
Iterate or Loop
Write Output

5. Sequence Control Structures
Sequence control structures direct the order of program instructions.
The fact that one instruction follows another—in sequence—establishes the control and order of operations.

6. Calculate Add 1 to Counter
A program can instruct a computer to perform mathematical operations.
Add 1 to Counter

7. Store
A program will often instruct a computer to store intermediate results.
Place 1 in Counter

8. Compare and Branch
A program can instruct a computer to compare two items and do something based on a match or mismatch which, in turn, redirect the sequence of programming instructions.
There are two forms:
IF-THEN
IF-THEN-ELSE

9. IF-THEN
false
true
Entry
Exit
True statement a
Test condition p

10. IF-THEN-ELSE Entry Exit Test condition p “true” statement a
false
true
Entry
Exit
Test condition p
“true” statement a
“false” statement a

11. Iterate
A program loop is a form of iteration. A computer can be instructed to repeat instructions under certain conditions. No

12. Iteration Control Structures
Iteration control structures are looping mechanisms.
Loops repeat an activity until stopped. The location of the stopping mechanism determines how the loop will work:
Leading decisions
Trailing decisions

13. Leading Decisions
If the stop is at the beginning of the iteration, then the control is called a leading decision.
The command DO WHILE performs the iteration and places the stop at the beginning.

14. DO WHILE Loop No
Yes
Entry
Exit
Test condition p
Loop statement a

15. Trailing Decisions
If the stop is at the end of the iteration, the control mechanism is called a trailing decision.
The command DO UNTIL performs the iteration and puts the stop at the end of the loop.

16. DO UNTIL Loop No
Yes
Entry
Test condition p
Exit
Loop statement a

17. Programs are Solutions to Problems
Programmers arrive at these solutions by using one or more of these devices:
Logic flowcharts
Structure charts
Pseudocode
Structured Programming

18. Logic Flowcharts
These represent the flow of logic in a program and help programmers “see” program design.

19. Common Flowchart Symbols
Terminator. Shows the starting and ending points of the program. A terminator has flowlines in only one direction, either in (a stop node) or out (a start node).
Data Input or Output. Allows the user to inputdata and results to be displayed.
Processing. Indicates an operation performed by the computer, such as a variable
assignment or mathematical operation.
Decision. The diamond indicates a decision structure. A diamond always has two
flowlines out. One flowlineout is labeled the “yes” branch and the other is labeled the
“no” branch.
Predefined Process. One statement denotes a group of previously defined statements.
For instance, “Calculate m!” indicates that the program executes the necessary commands
to compute m factorial.
Connector. Connectors avoid crossing flowlines, making the flowchart easier to read.
Connectors indicate where flowlines are connected. Connectors come in pairs, one with
a flowline in and the other with a flowline out.
Off-page connector. Even fairly small programs can have flowcharts that extend several
pages. The off-page connector indicates the continuation of the flowchart on another
page. Just like connectors, off-page connectors come in pairs.
Flowline. Flowlines connect the flowchart symbols and show the sequence of operations during the program execution.
Common Flowchart Symbols

20. Flowchart for a Cash Register Program
Start
sum=0
Input price
sum=sum+price
More
items?
tax=sum x
total=sum+tax
Output sum, tax,
and total
Stop No
Yes

21. Structure Charts
Structure charts illustrate the structure of a program by showing independent hierarchical steps.
Major divisions are subdivided into smaller pieces of information.

22. Psuedocode
This device is not visual but is considered a “first draft” of the actual program.
Pseudocode is written in the programmer’s native language and concentrates on the logic in a program—not the syntax of a programming language.

23. Pseudocode for a Cash Register Program
sum=0
While More items do
Input price
sum=sum+price
End While
tax=sum x
total=sum+tax
Output sum, tax, total

24. Structured Programming
Structured program languages lend themselves to flowcharts, structure charts, and pseudocode.
Structured programming languages work best where the instructions have been broken up into small, manageable parts.

25. The Program Development Cycle
Analyze the problem
Design the solution algorithm
Design the user interface
Write the code
Test and debug the program
Complete the documentation

26. Levels of Programming Languages
Machine language
Assembly Language
High Level Languages
Fourth Generation Languages (4GL)

27. Machine Languages
different for each computer processor
0100
01110
111001
. . .

28. Assembly Languages main proc pay mov ax, dseg mov ax, 0b00h add ax, dx
different for each computer processor
main proc pay
mov ax, dseg
mov ax, 0b00h
add ax, dx
mov a1, b1
mul b1, ax
mov b1, 04h

29. High-Level Languages Higher Level Languages 4GLs
Use traditional programming logic where the programming instructions tell the computer what to do and how to perform the required operations.
4GLs
Use high-level English-like instructions to specify what to do, not how to do it .

30. Interpreter vs Compiler
Translates instructions to machine code line-by-line.
Compiler
Translates the entire program to machine code before running it.

31. Types of Programming Languages
Machine language
Procedure-oriented languages
Object-oriented languages
Event-driven languages

32. Procedure-Oriented Languages
FORTRAN
COBOL
Pascal C
Ada

33. OOED Languages Object-oriented languages Event-driven languages
Smalltalk
C++
Ada 95
Event-driven languages
Visual Basic
most Visual languages

34. Programmer’s Lingo
Program - detailed set of instructions for a computer
Programming Language - tool used to create a program; defined by semantics and syntax
Semantics - the meaning of words in a language
Syntax - rules for combining symbols of a language

35. Programmer’s Lingo
Source Code (code) - program you write using a programming language
Interpreter - translates and executes source code statement by statement

36. Programmer’s Lingo
Interpreter Process

37. Programmer’s Lingo
Compiler Process