Input output

Input - Process - Output

in VB.NET

1

Objectives
Distinguish between logic and syntax
Understand and use the input statement
Understand and use the assignment
statement
Understand and use the output statement
Understand and use arithmetic operators
with precedence
Successfully write program solutions that
require input, processing, and output
2

Logic and Syntax
A computer program is a solution to a
problem.
An algorithm is the logical design used to
accomplish a specific objective.
Syntax refers to the specific rules of a
programming language.

3

Input Statements
An input statement accepts data from the
user and stores that data into a variable.
A variable is a storage location that can be
accessed and changed by developer code.
A variable has a name and an associated
data value.
A variable has a data type that determines
the kind of data values the variable can
store.

5

Declaring Variables
Variables are declared with the Dim
statement (short for Dimension statement).
One or more variables can be declared with
a single Dim statement.
The Dim statement can be used to specify
the variable’s initial value by placing an
equal sign after the data type.

6

Naming Rules for Variables
A variable must have a unique name, called
an identifier.
Identifiers must follow three rules:
 Begin with a letter or underscore
 Contain only letters, digits, and underscores
 Cannot be reserved words

Dim identifier [, identifier] [As datatype [= initialvalue]]

7

Working with Constants
A constant is a storage location whose
value cannot change during the execution
of the program.
Constants are declared with the Const
declaration.
Const identifier As datatype = value

8

Data Type
Data Type Description
String Text
Byte (1 byte) Positive Whole Number (0 to 255)
Short (2 bytes) Whole Number (-32,768 to 32,767)
Integer (4 bytes) Whole Number (+ or – up to 2 million)
Long (8 bytes) Whole Number (huge!)
Single (4 bytes) Floating point (+ or – up to 3.4 x 1038)
Double (8 bytes) Floating point (+ or – up to 1.8 x 10308)
Decimal Stored exactly as BCD (currency & percentages)
Date Also stores time
Boolean True or false
Char Single character or positive number (up to 65535)

9

Weekly Paycheck Program
The weekly
paycheck program
has two input
variables:
Hours and Rate

10

Operators and Expressions
An operator is a symbol that indicates an
action to be performed.
Value-returning code elements such as
variables, constants, and expressions can be
combined with one or more operators to
form an expression.

11

Assignment Statements
The assignment
statement can be used
to perform a
calculation and store
the result.
An expression is a
value-returning code
element, such as a
variable or
mathematical formula.

12

The Assignment Statement
An assignment statement is used to store a
value into a variable or an object property.
 variable = expression
 object.property = expression
The equal sign (=) is the assignment
operator.

13

Numbers and String Operators

Arithmetic operators require numeric
operands and produce numeric results.
The string operator concatenation (&)
requires String operands and produces a
String result such as:
 S = “sun” & “set”
 S becomes “sunset”

14

Numerical Operators
Operation Operator Expression 1 Result 1 Expression 2 Result 2

Plus &
+ – 4–5+2 1 4 – (5 + 2) -3
Minus
Multiply &
* / 1+3*7 22 17 / 3 5.667
Divide
Integer
12 4 3 17 3 5
Division
Integer
Mod 12 Mod 4 0 17 Mod 3 2
Remainder
Exponent
^ 5^2+1 26 5 ^ (2 + 1) 125
(Power of)

15

How to Write Formulas

16

Output Statements
(flow chart)

17

Intrinsic Functions
VB .NET provides a large number of
intrinsic functions to improve developer
productivity.
Intrinsic functions support a broad range of
activities, including math calculations,
business calculations, time and date
functions, string formatting functions, and
many more.

18

Common Functions
Intrinsic functions are predefined commands that
provide developers with common functions.
Function Example 1 Result 1 Example 2 Result 2

Val() (“23.5”) 23.5 (“£32”) 0

IsNumeric() (“23.5”) True (“£32”) True

FormatCurrency() (1234.567) £1,234.57 (4.5) £4.50

Format(expr,str) (1/2, “0.##”) “0.5” (6.666, “0.###”) “6.67”

Int() (3.8) 3 Int(Rnd()) 0

Double value Integer
Rnd() () Int(Rnd()*6)+1
between 0 and 1 from 1 to 6
Abs()
(-3.3) 3.3 (5.67) 5.67
Import System.Math
19

Rnd Statement
The Rnd statement generates a single
precision random value between 0.0 up
to (but not including) 1.0.
The Randomize statement is used to
change the seed value (random
sequence).

20

Financial Functions
Pmt is a function for determining monthly
payments.
 Pmt(Rate, NPer, PV)
FV is a function for determining the future
value of an annuity based on periodic, fixed
payments and a fixed interest rate.
 FV(Rate, NPer, Pmt)

21

Summary
Variables are storage locations used for holding input
and processing information.
 Each variable has two components: its name and its value.
 It is good practice to make variable names descriptive with
mixed case.
 The Dim statement is used to declare a variable by
specifying its name and data type.
Input statements are used to get data into variables.
Assignment statements are used to perform
calculations and store the result.

22

Summary
Expressions are combinations of operators and
value-returning code elements such as variables,
constants, and literals.
 One of the common uses of an expression is to perform
a calculation for an assignment statement.
 Intrinsic functions provide pre-defined methods for
common processing requirements.
Output statements are used to display
information.
Input, assignment, and output statements are
sufficient to write small programs.

23

Input output

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