Data Types and Variables in C#: Numeral Types, Text Types, and Type Conversion, Slides of Programming Languages

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Numeral Types, Text Types and Type Conversion

Data Types and Variables

Table of Contents

1. Data Types and Variables

2. Integer and Real Number Type

3. Type Conversion

4. Boolean Type

5. Character and String Type

 Computers are machines that process data

 Instructions and data are stored

in the computer memory

How Computing Works?

 Variables have name, data type and value

 Assignment is done by the operator "="

 Example of variable definition and assignment in C#

 When processed, data is stored back into variables

Variables

Data type int count = 5;

Variable name

Variable value

 A data type has:  Name (C# keyword or .NET type)  Size (how much memory is used)  Default value  Example:  Integer numbers in C#  Name: int  Size: 32 bits (4 bytes)  Default value: 0 Data Type Characteristics

int: sequence of 32

bits in the memory

int: 4 sequential bytes

in the memory

 Always refer to the naming conventions

of a programming language – for C# use camelCase

 Preferred form: [Noun] or [ Adjective] + [Noun]

 Should explain the purpose of the variable (Always

ask yourself " What this variable contains? ")

Naming Variables

firstName, report, config, fontSize, maxSpeed

foo, bar, p, p1, LastName, last_name, LAST_NAME

 Variable span is how long before a variable is called

 Always declare a variable as late as possible (e.g. shorter span)

static void Main()

string outer = "I'm inside the Main()";

for (int i = 0; i < 10; i++)

string inner = "I'm inside the loop";

Console.WriteLine(outer);

//Console.WriteLine(inner); Error

Variable Span

"outer"

variable span

for (int i = 0; i < 10; i++)

string inner = "I'm inside the loop";

string outer = "I'm inside the Main()";

Console.WriteLine(outer);

// Console.WriteLine(inner); Error

 Shorter span simplifies the code

 Improves its readability and maintainability

Keep Variable Span Short

"outer" variable

span – reduced

Type Default Value Min Value Max Value Size sbyte 0 - 128 (- 2 7 ) 127 ( 2 7

**- 1 ) 8 bit byte 0 0 255 ( 2 8

• 1 ) 8 bit short 0 - 32768 (- 2 15 ) 32767 ( 2 15
• 1 ) 16 bit ushort 0 0 65535 ( 2 16
• 1 ) 16 bit int 0 - 2147483648 (- 2 31 ) 2147483647 ( 2 31
• 1. 32 bit uint 0 0 4294967295 ( 2 32
• 1 ) 32 bit long 0
• 9223372036854775808 (- 2 63 ) 9223372036854775807 ( 2 63
• 1 ) 64 bit ulong 0 0 18446744073709551615 ( 2 64
• 1 ) 64 bit Integer Types**

 Depending on the unit of measure we can use different data types:

Centuries – Example

byte centuries = 20;

ushort years = 2000;

uint days = 730484;

ulong hours = 17531616;

Console.WriteLine(

"{0} centuries = {1} years = {2} days = {3} hours.",

centuries, years, days, hours);

//20 centuries = 2000 years = 730484 days = 17531616 hours.

 Examples of integer literals:

 The '0x' and '0X' prefixes mean a hexadecimal value

 E.g. 0xFE, 0xA8F1, 0xFFFFFFFF

 The 'u' and 'U' suffixes mean a ulong or uint type

 E.g. 12345678U, 0U

 The 'l' and 'L' suffixes mean a long

 E.g. 9876543L, 0L Integer Literals

 Read four integers

 Add first to the second

 Divide the sum by the third number (integer division)

 Multiply it by the fourth number

 Print the result

Problem: Integer Operations 10 20 3 3 30 20 30 2 3 75 15 14 2 3 42

Real Number Types

 Floating-point types:

 Represent real numbers, e.g. 1.25, - 0.

 Have range and precision depending

on the memory used

 Sometimes behave abnormally in the calculations

 May hold very small and very big values like

0.00000000000001 and

What are Floating-Point Types?