Programming Languages

1

• Programming Languages
• I Generation Machine Language
• II Gen Assembly Language
• III Gen Procedural languages
• Basic, Fortran, Cobol, .
• Compile ? Link Edit ? Execute
• IV Gen PowerBuilder, HTML
• Object Oriented ProgrammingC, Java, Small Talk

2

• Object Information and operations that can be
  performed on that information.
• Object Bank Account
• Information 3,000 in the bank account
• Operations Balance, withdraw, deposit
• Object encapsulates (packages) data with
  operations.

3

• Linking Applications
• OLE Object Linking and Embedding
• Linking Points to the object in another
  application
• Embedding Copies the object of other application
  into this object.

4

• Basic Programming
• Early Language (60s)
• Developed by undergrads
• Easy
• Small Set of Commands

5
.0

• Procedural Languages
• Before GUI
• Execution of the program statements is from
  top to bottom
• Text-based
• Qbasic comes with M operating systems.

6

• Visual Basic
• Event Driven Language
• What to do under various events is specified
• Events Moves mouse, click a button,
• double click, menu selection,
• GUI
• Users May not do things in the same order
• Order of program execution is dictated by user.

7
VisualBasic

• Event-Driven What the program does depends on
  user actions
• User scrolls on Horizontal/vertical scroll bars
• User clicks on a button
• User checks a selection box. .
• User Clicks on a command button.

8

• Variables
• Name must begin with a letter
• In many programming languages length may be a
  restriction.
• Short but mnemonic
• No spaces in variable names. Use or _ to
  improve readability. Currentwages or
  current_wages but not current wages
• Number1 for the amount invested may not be
  mnemonic. Principal is better.
• Not a reserved word like print, input, end .

9

• Variable Types
• Integer (whole numbers -32768 to 32767)
• Long (Larger whole numbers than above)
• single (decimal numbers with 6 digits of
  accuracy)
• double (decimal numbers with 14 digits of
  accuracy)
• currency, Date
• string (Alpha numeric data)
• variant (any numeric)
• Boolean (true or false)
• You specify the variable type by
• DIM my_variable as double

10

• Assignment of a value to a variable and
  Arithmetic
• Dim principal as double
• Assignment of value
• principal 100
• Arithmetic add 10 to principal
• principal principal 10

11

• Arithmetic Operations
• principal principal principal interest
• This says multiply principal by interest and add
  to old principal and assign to principal
• If values of principal is 1000 and interest is .2
  before the above statement is executed, the
  statement is equivalent to
• Principal 1000 1000 .2
• The vale of principal after execution of the
  statement is 1200

12

• Order of Arithmetic
• 2 4 10 ? 60 or 42?
• - (negation) (exponentiation) ( /) ( -)
• Comparisons
• lt gt lt gt ltgt (lt and gt
  together)
• Logical Comparisons
• Not And Or XOR

13

• Order of Arithmetic
• Exercise 4 -2 8 5 / 2
• Could be very confusing.
• Use parentheses to specify order of arithmetic.
• Stuff in parentheses are evaluated first.
• If parentheses are nested, inner to outer set of
  parentheses.
• Above operation can be written as
• ((4 -2) 8) (5 / 2) 1/16 8 2.5 3

14

• Decisions
• If-Then-Else
• Syntax
• If condition Then true-task else false-task end
  if
• If quantity gt 100 then price 4 else price 5
  end if
• condition true-tak
  false-task
• If prin gt 1000000 then print you are rich!
• Why no ,? What does this do?

15

• Program Flow
• Usual program flow is from top to bottom, but it
  can be changed.
• For .. Next Loop repeats execution of a group
  statements as many times as we need.
• For index 1 to 1000
• ..
• ..
• Next index
• The statements .. Will be repeated 1,000 times.
• The value of index will increase by 1 each time
  for statement is executed.

16

• Program Flow
• Do While Loop
• Do While prin gt0 and prin lt 1000
• .
• .
• Loop
• How many times will the statements in the loop be
  executed? Depends!
• Infinite Loop

17

• Exercise 20 for first 100 units, 15 for
  additional units.
• If units lt 100 then bill units 20 else bill
  10020 (units 100) 15

18

• Same result can be accomplished many ways.
• An alternative
• If units gt 100 then bill 15 units 500
• Else bill 20 units
• End If

19

• Exercise To add numbers 1 thru 10
• For Next Loop
• sum 0
• for numb 1 to 10
• sum sum numb
• next numb
• numb is an index. It starts at 1 and goes up to
  10. The value of it is increased by 1 every time
  for statement is executed.
• First time thru the loop, numb is 1, next time 2,
  
• How many times will the loop be executed?

20
Sum 0For numb 1 to 10sum sum numbNext
numb
21

• Exercise
• Compute FICA deductions.
• FICA (Social Security) withholdings are 7.65 of
  your gross wages up to 72,600
• Have cumulative to last paycheck (cum_wage) and
  current period gross income (gross_wage)
  available. Compute FICA deduction.
• Write the code on a sheet of paper and turn it in
  with your name.

22

• Flow Chart of FICA Problem

Gross Cum lt 72600
Fica .0765 gross
T
F
Cum gt 72600
Fica 0
T
F
Fica (72600- cum) .0765
23

• Suggested Solution 1
• If gross_wage cum_wage lt 72600 Then fica
  0.0765 gross_wage
• If gross_wage cum_wage gt 72600 And cum_wage lt
  72600 Then fica (72600 - cum_wage) 0.0765
• If cum_wage gt 72600 Then fica 0
• Suggested Solution 2
• If gross_wage cum_wage lt 72600 Then
• fica 0.0765 gross_wage
• ElseIf cum_wage gt 72600 Then
• fica 0
• Else fica (72600 - cum_wage) 0.0765
• End If
• Both of them give the same results.