Chapter 2. Introduction to C

1
Chapter 2. Introduction to C
2
2.1 The Parts of a C Program

• C programs have parts and components that serve
  specific purposes.

3
Program 2-1

• //A simple C program
• include ltiostream.hgt
• void main (void)
• coutltlt Programming is great fun!
• Program Output
• Programming is great fun!

4
Table 2-1
5
2.2 The cout Object

• Use the cout object to display information on the
  computers screen.
• The cout object is referred to as the standard
  output object.
• Its job is to output information using the
  standard output device

6
Program 2-2

• // A simple C program
• include ltiostream.hgt
• void main (void)
• coutltlt Programming is ltlt great fun!
• Output
• Programming is great fun!

7
Program 2-3

• // A simple C program
• include ltiostream.hgt
• void main (void)
• coutltlt Programming is
• cout ltlt great fun!
• Output
• Programming is great fun!

8
Program 2-4

• // An unruly printing program
• include ltiostream.hgt
• void main(void)
• cout ltlt "The following items were top sellers"
• cout ltlt "during the month of June"
• cout ltlt "Computer games"
• cout ltlt "Coffee"
• cout ltlt "Aspirin"
• Program Output
• The following items were top sellersduring the
  month ofJuneComputer gamesCoffeeAspirin

9
New lines

• cout does not produce a newline at the end of a
  statement
• To produce a newline, use either the stream
  manipulator endl
• or the escape sequence \n

10
Program 2-5

• // A well-adjusted printing program
• include ltiostream.hgt
• void main(void)
• cout ltlt "The following items were top sellers"
  ltlt endl
• cout ltlt "during the month of June" ltlt endl
• cout ltlt "Computer games" ltlt endl
• cout ltlt "Coffee" ltlt endl
• cout ltlt "Aspirin" ltlt endl

11
Program Output

• The following items were top sellers
• during the month of June
• Computer games
• Coffee
• Aspirin

12
Program 2-6

• // Another well-adjusted printing program
• include ltiostream.hgt
• void main(void)
• cout ltlt "The following items were top sellers"
  ltlt endl
• cout ltlt "during the month of June" ltlt endl
• cout ltlt "Computer games" ltlt endl ltlt "Coffee"
• cout ltlt endl ltlt "Aspirin" ltlt endl

13
Program Output

• The following items were top sellers
• during the month of June
• Computer games
• Coffee
• Aspirin

14
Program 2-7

• // Yet another well-adjusted printing program
• include ltiostream.hgt
• using namespace std
• void main(void)
• cout ltlt "The following items were top
  sellers\n"
• cout ltlt "during the month of June\n"
• cout ltlt "Computer games\nCoffee"
• cout ltlt "\nAspirin\n"

15
Program Output

• The following items were top sellers
• during the month of June
• Computer games
• Coffee
• Aspirin

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Table 2-2
17
2.3 The include Directive

• The include directive causes the contents of
  another file to be inserted into the program
• Preprocessor directives are not C statements
  and do not require semicolons at the end

18
2.5 Variables and Constants

• Variables represent storage locations in the
  computers memory. Constants are data items
  whose values do not change while the program is
  running.
• Every variable must have a declaration.

19
Program 2-8

• include ltiostream.hgt
• void main(void)
• int value
• value 5
• cout ltlt The value is ltlt value ltlt endl
• Program Output
• The value is 5

20
Assignment statements

• Value 5 //This line is an assignment
  statement.
• The assignment statement evaluates the expression
  on the right of the equal sign then stores it
  into the variable named on the left of the equal
  sign
• The data type of the variable was in integer, so
  the data type of the expression on the right
  should evaluate to an integer as well.

21
Constants

• A variable is called a variable because its
  value may be changed. A constant, on the other
  hand, is a data item whose value does not change
  during the programs execution.

22
Program 2-10

• include ltiostream.hgt
• void main (void)
• int apples
• apples 20
• coutltlt Today we sold ltlt apples ltlt
  bushels\n
• cout ltlt of apples.\n

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Program Output

• Today we sold 20 bushels
• of apples.
• Where are the constants in program 2-10?

24
Constants from Program 2-10
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2.6 Focus on Software Engineering Identifiers

• Must not be a key word
• Should be mnemonic (give an indication of what
  the variable is used for)
• The first character must be a letter or an
  underscore
• The remaining may be letters, digits, or
  underscores
• Upper and lower case letters are distinct

26
Table 2-3 The C Key Words
27
Table 2-4 Some Variable Names
28
2.7 Integer Data Types

• There are many different types of data.
  Variables are classified according to their data
  type, which determines the kind of information
  that may be stored in them. Integer variables
  only hold whole numbers.

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Table 2-5
30
Program 2-11

• // This program has variables of several of the
  integer types.
• include ltiostream.hgt
• void main(void)
• int checking
• unsigned int miles
• long days
•   checking -20
• miles 4276
• days 184086
• cout ltlt "We have made a long journey of " ltlt
  miles
• cout ltlt " miles.\n"
• cout ltlt "Our checking account balance is " ltlt
  checking
• cout ltlt "\nExactly " ltlt days ltlt " days ago
  Columbus "
• cout ltlt "stood on this spot.\n"

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Program Output

• We have made a long journey of 4276 miles.
• Our checking account balance is -20
• Exactly 184086 days ago Columbus stood on this
  spot.

32
Program 2-12

• // This program shows three variables declared on
  the same
• // line.
• include ltiostream.hgt
•  
• void main(void)
• int floors,rooms,suites
•  
• floors 15
• rooms 300
• suites 30
• cout ltlt "The Grande Hotel has " ltlt floors ltlt "
  floors\n"
• cout ltlt "with " ltlt rooms ltlt " rooms and " ltlt
  suites
• cout ltlt " suites.\n"

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Program Output

• The Grande Hotel has 15 floors
• with 300 rooms and 30 suites.

34
Hexadecimal and Octal Constants

• Hexadecimal numbers are preceded by 0x
• Hexadecimal F4 would be expressed in C as 0xF4
• Octal numbers are preceded by a 0
• Octal 31 would be written as 031

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2.8 The char Data Type

• Usually 1 byte long
• Internally stored as an integer
• ASCII character set shows integer representation
  for each character
• A 65, B 66, C 67, etc.
• Single quotes denote a character, double quotes
  denote a string

36
Program 2-13

• // This program demonstrates the close
  relationship between
• // characters and integers.
• include ltiostream.hgt
• void main(void)
• char letter
•  
• letter 65
• cout ltlt letter ltlt endl
• letter 66
• cout ltlt letter ltlt endl

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Program Output

• A
• B

38
Program 2-14

• // This program uses character constants
• include ltiostream.hgt
• void main(void)
• char letter
•  
• letter 'A'
• cout ltlt letter ltlt endl
• letter 'B'
• cout ltlt letter ltlt endl

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Program Output

• A
• B

40
C-Strings

• C-Strings are consecutive sequences of characters
  and can occupy several bytes of memory.
• C-Strings always have a null terminator at the
  end. This marks the end of the string.
• Escape sequences are always stored internally as
  a single character.

41
Program 2-15

• // This program uses character constants
• include ltiostream.hgt
• void main(void)
• char letter
•  
• letter 'A'
• cout ltlt letter ltlt '\n'
• letter 'B'
• cout ltlt letter ltlt '\n'

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Program Output

• A
• B

43
Review key points regarding characters, strings,
and C-strings

• Printable characters are internally represented
  by numeric codes. Most computers use ASCII codes
  for this purpose.
• Characters occupy a single byte of memory.
• C-Strings are consecutive sequences of characters
  and can occupy several bytes of memory.
• C-Strings always have a null terminator at the
  end. This marks the end of the C-string.
• Character constants are always enclosed in single
  quotation marks.
• String constants are always enclosed in double
  quotation marks.
• Escape sequences are always stored internally as
  a single character.

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2.9 The C string Class

• The string class is an abstract data type.
• It provides capabilities that make working with
  strings easy and intuitive.
• You must us the include ltstringgt statement.

45
2.10 Floating Point Data Types

• Floating point data types are used to declare
  variables that can hold real numbers

46
Table 2-7
47
Program 2-17

• // This program uses floating point data types
• include ltiostream.hgt
• void main(void)
• float distance
• double mass
• distance 1.495979E11
• mass 1.989E30
• cout ltlt "The Sun is " ltlt distance ltlt "
  kilometers away.\n"
• cout ltlt "The Sun\'s mass is " ltlt mass ltlt "
  kilograms.\n"

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Program Output

• The Sun is 1.4959e11 kilometers away.
• The Sun's mass is 1.989e30 kilograms.

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Floating Point Constants

• May be expressed in a variety of ways
• E notation
• decimal notation
• (no commas)

50
2.11 The bool Data Type

• Boolean variables are set to either true or false

51
Program 2-18

• include ltiostream.hgt
• void main (void)
• bool boolValue
• boolValue true
• cout ltlt boolValue ltlt endl
• boolValue false
• cout ltlt boolValue ltlt endl

52
Program Output

• 1
• 0
• Internally, true is represented as the number 1
  and false is represented by the number 0.

53
2.12 Focus on Software Engineering Determining
the Size of a Data Type

• The sizeof operator may be used to determine the
  size of a data type on any system.
• cout ltlt The size of an integer is ltlt
  sizeof(int)

54
Program 2-19

• include ltiostream.hgt
• void main (void)
• long double apple
• cout ltlt The size of an integer is ltlt
  sizeof(int)
• cout ltlt bytes.\n
• cout ltlt The size of a long integer is ltlt
  sizeof(long)
• cout ltlt bytes.\n
• cout ltlt An apple can be eaten in ltlt
  sizeof(apple)
• cout ltlt bytes!\n

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Program Output

• The size of an integer is 4 bytes.
• The size of a long integer is 4 bytes.
• An apple can be eaten in 8 bytes!

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2.13 Focus on Software Engineering Variable
Assignment and Initialization

• An assignment operation assigns, or copies, a
  value into a variable. When a value is assigned
  to a variable as part of the variables
  declaration, it is called an initialization.

57
Program 2-20

• include ltiostream.hgt
• void main (void)
• int month 2, days 28
• cout ltlt Month ltlt month ltlt has ltlt days ltlt
  days.\n
• Program output
• Month 2 has 28 days.

58
2.14 Focus on Software Engineering Scope

• A variables scope is the part of the program
  that has access to the variable.
• A variable must be declared before it is used.

59
Program 2-21

• // This program can't find its variable
• include ltiostream.hgt
• void main(void)
• cout ltlt Value
•  
• int Value 100

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2.15 Arithmetic Operators

• There are many operators for manipulating numeric
  values and performing arithmetic operations.
• Generally, there are 3 types of operators unary,
  binary, and ternary.
• Unary operators operate on one operand
• Binary operators require two operands
• Ternary operators need three operands

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Table 2-8
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Program 2-22

• // This program calculates hourly wages
• // The variables in function main are used as
  follows
• // regWages holds the calculated regular wages.
• // basePay holds the base pay rate.
• // regHours holds the number of hours worked
  less overtime.
• // otWages holds the calculated overtime wages.
• // otPay holds the payrate for overtime hours.
• // otHours holds the number of overtime hours
  worked.
• // totalWages holds the total wages.
•  
• include ltiostream.hgt
• void main(void)
• float regWages, basePay 18.25, regHours
  40.0
• float otWages, otPay 27.78, otHours 10
• float totalWages
•  
• regWages basePay regHours

63
2.16 Comments

• Comments are notes of explanation that document
  lines or sections of a program.
• Comments are part of a program, but the compiler
  ignores them. They are intended for people who
  may be reading the source code.
• Commenting the C Way
• //
• Commenting the C Way
• / /

64
Program 2-23

• // PROGRAM PAYROLL.CPP
• // Written by Herbert Dorfmann
• // This program calculates company payroll
• // Last modification 3/30/96
•  
• include ltiostream.hgt
•  
• void main(void)
• float payRate // holds the hourly pay rate
• float hours // holds the hours worked
• int empNum // holds the employee number
•  
• (The remainder of this program is left out.)

65
Program 2-24

• // PROGRAM PAYROLL.CPP
• // Written by Herbert Dorfmann
• // Also known as "The Dorfmiester"
• // Last modification 3/30/96
• // This program calculates company payroll.
• // Payroll should be done every Friday no later
  than
• // 1200 pm. To start the program type PAYROLL
  and
• // press the enter key.
•  
• include ltiostream.hgt // Need the iostream file
  because
• // the program uses cout.
• void main(void) // This is the start of
  function main.
• // This is the opening brace for main.
• float payRate // payRate is a float variable.
• // It holds the hourly pay rate.
• float hours // hours is a float variable too.
• // It holds the hours worked.
• int empNum // empNum is an integer.
• // It holds the employee number.

66
Program 2-25

• /
• PROGRAM PAYROLL.CPP
• Written by Herbert Dorfmann
• This program calculates company payroll
• Last modification 3/30/96
• /
• include ltiostream.hgt
• void main(void)
• float payRate / payRate holds hourly pay rate
  /
• float hours / hours holds hours worked
  /
• int empNum / empNum holds employee number
  /
•  
• (The remainder of this program is left out.)

67
Program 2-26

• /
• PROGRAM PAYROLL.CPP
• Written by Herbert Dorfmann
• This program calculates company payroll
• Last modification 3/30/96
• /
• include ltiostream.hgt
• void main(void)
• float payRate // payRate holds the hourly pay
  rate
• float hours // hours holds the hours worked
• int empNum // empNum holds the employee number
•  
• (The remainder of this program is left out.)

68
2.17 Focus on Software Engineering Programming
Style

• Program style refers to the way a programmer uses
  identifiers, spaces, tabs, blank lines, and
  punctuation characters to visually arrange a
  programs source code.
• Generally, C ignores white space.
• Indent inside a set of braces.
• Include a blank line after variable declarations.

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Program 2-27

• include ltiostream.hgt
• void main(void)float shares220.0float
  avgPrice14.67cout ltlt"There were "ltltsharesltlt"
  shares sold at "ltltavgPriceltlt" per share.\n"
• Program Output
• There were 220 shares sold at 14.67 per share.

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Program 2-28

• // This example is much more readable than
  Program 2-26.
•  include ltiostream.hgt
• void main(void)
• float shares 220.0
• float avgPrice 14.67
•  
• cout ltlt "There were " ltlt shares ltlt " shares sold
  at "
• cout ltlt avgPrice ltlt " per share.\n"
• Program Output
• There were 220.0 shares sold at 14.67 per share.