Transcript Lecture 4 - Suraj @ LUMS

Programming Fundamentals
Chapter 4
Floating Point Numbers
 Scientific notation
98 = 0.98 x 102
204.5 = 0.2045 x 103
-0.082167 = -0.82167 x10-1
 Sign bit; Fraction (Mantissa); Exponent
S
Sign
Bit
Exponent
Fraction
Floating point arithmetic
 Addition & Subtraction
0.45x102 + 0.32x101 =
-0.45x102 - 32x101 =
 Multiplication & Division
0.45x102 ÷ 0.32x10-1 =
0.45x102 * 0.32x10-1 =
Data Types
 Type of quantities
 Integer
 Long Integer
 Single
 Double
 String
 Byte
 Boolean
 Currency
 Date
Integer & Long Integer
 Integer
– Uses 2 bytes ( 2x8=16 bits ) of memory
-32768  +32767 range
– No commas, like 20,400
– No decimals or fractions, like 2.45 or 4.00
 Long Integer
– Uses 4 bytes
-2147483648  +2147483647 range
Single & Double
 Single
– Use 4 bytes (32 bits)
– Can have 7 significant digits
-3.4E38  3.4E38 range
 Double
– Uses 8 bytes (64 bits)
– Can have 15 significant digits
-1.8D308  1.8D308 range
Byte & Currency
 Byte
– Unsigned numbers
0  255
 Currency
– 8 Bytes
-922,337,203,685,477.5808 
+922,337,203,685,477.5808
– No truncation & rounding
String
 Strings are non-numeric quantities, written
within quotes
– Examples
 “Islam is the solution to world problems”
 “CS101”
 “-423.45”
 “Rs. 32,400.55”
 “TB stands for Tooni’s Blare & a notorious disease”
Constants & Variables
 Each data type can be a constant or a
variable
 Constant
– The contents of the memory remain fixed
– Numeric or String
pi  3.14
Speed Of Light  2.998e8
k  1.38e-23
Name Of My Hero  “Muhammad (pbuh)”
e  “-1.6e-19”
Constants & Variables
 Variables
– The contents of a memory associated with a
variable is allowed to change
Read A
Read B
Sum = A + B
Product = A*B
– A & B determine the contents of Sum and
Product
Declarations
 Variables are declared at the beginning of a
program using Dim
– Reserve appropriate memory
 Examples
–
–
–
–
–
Dim
Dim
Dim
Dim
Dim
MidtermScore As Integer
h As single, Frequency As Single
Energy As Double
StudentName As String
CourseTitle As String*40
Memory Allocation
A_Integer
A_Single
Variable Name Rules

A variable name must begin with an
alphabet.

It should not be longer than 255
characters.

Special words, such as, Dim, If, Else,
Case, etc. are not permitted.
Variable Name Rules

Some special characters are allowed
within a variable name.

A period (full stop), %, # and & are not
allowed.
– Avoid special characters in a variable name.
Variable Name Rules

Visual Basic does not distinguish between
upper and lower case letters.
– AVARIABLE, AVariable, aVariable,
avariable, etc. refer to the same memory
location.
The Longest Variable Name
 EvenThoughItIsHardToWriteOrReadAndMa
nyOfUsMayNeverSeeOrWriteSuchLongVari
ableNameYetVisualBasicAllowsTheUseOfT
woHundredFiftyFiveCharactersForTheVaria
bleName0123456789012345678901234567
89012345678901234567890123456789012
34567890123456789012345678901234567
89
 255 characters
Suffix Notation
Variable
Data Type
Index%
Integer
Counter&
Long Integer
TaxRate!
Single
Ratio#
Double
Name$
String
Constants
 Constants can be named like variables
– Or remain un-named
Const Name As String=“Muhammad (pbuh)”
Const c As Single = 2.998E8
Const e As Double = -1.6D-19
22.5
6/7
– An effort to change the contents of a named
constant will result in an error
Assignment to constants not permitted
Operators







+ (plus)
- (minus)
* (asterisk)
/ (slash)
^ (caret)
\ (back slash)
Mod
Addition
Subtraction
Multiplication
Division
Exponentiation
Integer division
Integer remainder
Shift + =
Shift + 8
/
Shift + 6
\
Operations







2^3 = 8
10/8 = 1.25
10\8 = 1
8.6\2.7 = 3
10 Mod 8 = 2
2.3 Mod 2.1 = 0
2.3/1.2^2 = 2.3/1.44 = 1.5972
Hierarchy of Operations
1.
2.
3.
4.
5.

(^)
(* or /)
(\)
(Mod)
(+ or -)
Exponentiation
Multiplication & Division
Integer Division
Integer Remainder
Addition & Subtraction
Parentheses are used to change the order
of operation.
Expressions
[2(a  b)2  3c2 ]3 2
 (2*(a+b)^2 + 3*c^2)^(3/2)
[2(a  b)  3c ]
3*c^2)^3/2 
2
2
(2*(a+b)^2 +

x  y
2
 -x + y^2
 -2^4 = -(2^4) = -16
 (-2)^4 = 16
2 3
String Expressions
Amount = “Ten”
Denomination = “Thousand”
Amount & “ “ & Denomination & “ Rupees”
  Ten Thousand Rupees
Amount + “ “ + Denomination + “ Rupees”
  Ten Thousand Rupees
Assignment
Salary = 12000
Tax = 4/100*Salary
HouseRent = 1200
NetSalary = Salary - Tax - HouseRent
Library Functions
 Abs
 Y=Abs(-2) 
Y=2
 Chr
 Y=Chr(65) 
Y = “A”
 Exp
 Y=Exp(2)

Y = e^2
 Int
 Y=Int(-2.9) 
Y = -3
Library Functions
 Rnd
 Y=Rnd

 Sgn
 Y=Sgn(x)

 Str
 Y=Str(4.2) 
Y gets a random number 0≤Y<1
Y  1 x  0

Y 0 x0
Y  1 x  0

Y = “4.2”
 Val
 Y=Val(“-3”)+Val(“2”)

Y = -3.1+2=-1.1
 The string within the Val must appear like a number
Library Functions
 Sin, Cos, Tan
– Trigonometric functions
 Arguments must be in RADIANS
– Sin(x), Cos(u), Tan(w)
 Date
Y=Date  Current date
mo/dy/Year
 Sqr
Y=Sqr(4)

Y=2=
4
Library Functions
 Lcase
Y=Lcase(“MyName”)  Y=“myname”
 Ucase
Y=Ucase(“MyName”)  Y = “MYNAME”
 Len
Y=Len(“MyName”)  Y=6
Library Functions
 Left
 Y=Left(“MyName”,3)  Y=“MyN”
 Right
 Y=Right(“MyName”,3)  Y=“ame”
 Mid
 Y=Mid(“MyName”,2,3)  Y=“yNa”
 Log
 Y=Log(72.4)  Y=loge(72.4)