How%20Create%20a%20C %20Program

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How Create a C Program
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• includeltiostreamgt
• using namespace std
• void main()
• coutltltHello World
• If your compiler gives error then

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• includeltiostream.hgt
• void main()
• coutltltHello World
• coutltltendl // for going to new line
• coutltlt good bye
• cout is an object for printing out some thing
• on the screen.

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• includeltiostream.hgt
• void main()
• coutltltHello World \n
• coutltlt good bye
• we can use \n instead of coutltltendl

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How to run your program

• Using Linux or unix
• g myFile.cpp
• ./a.out
• g myFile.cpp myFile.out
• ./myFile.out

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Declare Statement Variable

• Each variable must be declare before use
• Each variable has a type
• For example
• int , char, float.
• int for Integer type
• char for character like A
• float for real number

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Example

• int LuckyNumber17
• float RealNumber
• char aA

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Identifiers

• Identifier name of a variable, function, or
  class
• Rules for identifiers in C
• 1 Can be made up of letters, digits, and the
  underscore (_) character
• 2 Cannot start with a digit
• 3 Cannot use other symbols such as ? or
• 4 Spaces are not permitted inside
  identifiers
• 5 You cannot use reserved words
• 6 They are case sensitive

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Self Check

• 1. What is the type of the values 0 and 0?
• 2. Which of the following are legal identifiers?
• Greeting1gvoid101dalmatiansHello,
  Worldltgreetinggt

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Answer

• int and char
• Only the first two are legal identifiers

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Syntax Variable Definition

• typeName variableName valueor typeName
  variableName
• Example
• int number 12
• Purpose
• To define a new variable of a particular type and
  optionally supply an initial value

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The Assignment Operator

• Assignment operator
• Not used as a statement about equality
• Used to change the value of a variable
• int number1
• int number2, number3 number1number2number3
  88

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• number2number2-1
• number3number21

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How to read a variable

• includeltiostreamgt
• using namespace std
• void main()
• int number
• coutltltplease enter a number \n
• cingtgtnumber
• numbernumber1
• coutltltthe number is ltltnumber

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Integer Types

• The short, int and long Integer Types
• A short integer is at least 16 bits
• An int integer is at least as big as short
• A long integer is at least 32 bits and at
• least as big as int .

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• E.g. A 16-bit int might run from -32768 to 32767
• The sizeof operator returns the size (in bytes)

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• includeltiostream.hgt
• int main()
• int n_int INT_MAX
• short n_short SHRT_MAX
• long n_long LONG_MAX
• cout ltlt int is ltlt sizeof (int) ltlt bytes
  ltlt endl
• cout ltlt short ltlt n_short ltlt endl
• cout ltlt long ltlt n_long ltlt endl
• return 0

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• int is 4 bytes
• Maximum values
• Short 32767
• Long 2147483647

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Characters and small integers

• includeltiostream.hgt
• int main()
• char ch M // assign ASCII code
• int a ch
• cout ltlt ASCII code ltlt ch ltlt is ltlt a
  ltlt endl
• ch ch 1
• a ch
• cout ltlt ASCII code ltlt ch ltlt is ltlt a ltlt
  endl
• return 0

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Output

• M is 77
• N is 78

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Boolean type

• bool isReady true
• int ans true // ans assigned 1
• int promise false // promise assigned 0
• bool start -100 // true
• bool stop 0 // false

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Floating-point number

• E.g.
• 12.34
• 9300.3
• 0.02
• 8.0
• We have
• float, double, long double

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Arithmetic operators

• Summation
• Multiplication
• Division /
• Subtraction -

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Operator Precedence

• int number 3 4 5 // 35 or 23?
• float logs 120 / 4 5 // 150 or 6??

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Type Casting

• Conversion between types
• (typeName) value // c
• typeName (value) // c
• e.g.
• cout ltlt int(A) ltlt endl // 65
• float one,
• int two
• one 1.9 2.1
• two (int) 1.9 (int) 2.1