The Basic Language

1
The Basic Language

• Molloy College
• CIS103 Visual Basic
• Dr. Cohen

2
What Is a Program?

• 100 REM PROGRAM TO AVERAGE THREE NUMBERS
• 110 REM X, Y, AND Z DENOTE NUMBERS
• 120 REM A DENOTES AVERAGE

3
What Is a Program?

• 130 LET X43
• 140 LET Y27
• 150 LET Z23
• 160 LET A(X YZ)/3
• 170 PRINT AVERAGE IS, A
• 180 END

4
Output

• AVERAGE IS 31

5
Numerical Constants

• Integer 726 or 726
• Decimal 726.00 or 7.26
• Floating Point 1E4 1 X 104
• The value of a constant does not change during
  the program.

6
Numerical Variables

• A
• A1
• SUM
• Sum1
• The value of a variable can change during the
  program.

7
String Constants

• X
• Michael Jackson
• 726
• The value of a string constant remains unchanged
  during the program.

8
Assigning Value

• In Basic the Let statement assigns a value

9
Assigning Value

• If A2, B-2, C3, and AABC
• Then
• Let SABC S
• Let XA1 X
• Let Y4 Y
• Let RA R

10
Assigning Value

• If A2, B-2, C3, and AABC
• Then
• Let SABC S 3
• Let XA1 X 3
• Let Y4 Y 4
• Let RA R ABC

11
Assigning Value

• Let NN1
• If N6 Then
• NN1 assigns a value to N of

12
Assigning Value

• Let NN1
• If N6 Then
• NN1 assigns a value to N of 7
• Such expressions are used to create loops.

13
Interaction

• Input a variable or string
• 10 Input D
• 20 Let C12D
• If the user types D as 10 then C

14
Interaction

• Input a variable or string
• 10 Input D
• 20 Let C12D
• If the user types D as 10 then C22

15
Making Decisions

• 100 Input x
• 110 If xgt10 then T.5x
• 120 Else Tx
• If x6, what is T?
• If x12, what is T?

16
Making Decisions

• 100 Input x
• 110 If xgt10 then T.5x
• 120 Else Tx
• If x6, what is T? T3
• If x12, what is T? T12

17
Printing

• 100 Let K8
• 110 Print Tab(K)Tab(22-K)
• 120 Let KK1
• 130 If Klt10 Then 110
• 140 Print Tab(11)
• 150 END
• RUN What?

18
Printing

• 100 Let K8
• 110 Print Tab(K)Tab(22-K)
• 120 Let KK1
• 130 If Klt10 Then 110
• 140 Print Tab(11)
• 150 END
• RUN What?

19
OopsLoops!

• 200 For I1 to N
• 210 Print -
• 220 Next I
• Assume line 190 reads N15. What happens when
  the program is run?

20
OopsLoops!

• 200 For I1 to N
• 210 Print -
• 220 Next I
• Assume line 190 reads N15. What happens when
  the program is run?
• --------------- (15 dashes)

21
Hurrays! (Arrays)

• Variable G7
• Array G4 G5 G6 G7
• This format will confuse the computer!
• What should we write?

22
Hurrays! (Arrays)

• Variable G7
• Array G4 G5 G6 G7
• This format will confuse the computer!
• What should we write?
• G(1)4 G(2) 5 G(3)6 G(4)7

23
Hurrays! (Arrays)

• What should we write?
• G(1)4 G(2) 5 G(3)6 G(4)7

Every variable is an array.
24
Visual Basic

• Visual Basic is related to Basic. Unlike Basic,
  Visual Basic is designed to have objects with
  properties and buttons which trigger events.