CSci 152: Programming II Fall 2004

1
CSci 152 Programming IIFall 2004

• Review

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Programming Languages

• Programming language A set of rules, symbols and
  special words.
• syntax tells which statements are legal or
  accepted
• semantics determine meanings of instructions

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Basic Elements of C

• A C Program (or any program in a procedural
  programming language)
• Collection of 1 or more subprograms called
  functions
• Which is a collection of statements that can
  accomplish something useful
• sequence, selection, repetition
• Special function called main

4
Hello World!

• include ltiostreamgt
• using namespace std
• int main()
• cout ltlt Welcome to C Programming. ltlt
  endl
• return 0

5
C Tokens

• Special Symbols
• - / . ? , lt ! gt
• Word Symbols
• int, float, char, void, return
• Identifiers
• Identifiers are names of things that appear in
  programs, such as variables, constants, and
  functions.
• Some are predefined others are defined by you,
  the programmer.

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C Data Types

• def Data type A set of values together with a
  set of operations
• simple data type
• structure data type
• pointers

Cs Data types
Simple
Structured
Pointers
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Simple Data Types

• The simple data type is the fundamental data type
  in C, building block for the structured data
  type
• Integral, deals with integers or numbers withut a
  decimal part
• int, bool, char, short, long, unsigned variants
• Floating-point, deals with decimal numbers
• float, double, long double
• Enumeration type, which is a user-defined data
  type
• e.g. enum olympicSports basketball, volleyball,
  diving, swimming, trackAndField, marathon,
  archery

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Arithmetic Operators and Expressions

• - /
• Expressions
• 2 5
• 10 6
• x y / z (0.5 w)
• Type Conversion (Casting)
• float x float(24/7)

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Identifiers

• Identifier
• Identifier A C identifier consists of letters,
  digits, and the under score character (_), and
  must begin with a letter or underscore.
• C is case sensitiveuppercase and lower case
  letters are different.
• Some of the predefined identifiers are cout and
  cin.
• Unlike reserved words, pre-defined identifiers
  may be redefined, but it would not be wise to do
  so.

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Declaring Variables

• Storing data in the computers memory is a two
  step process.
• Instruct the computer to allocate memory.
• Include statements in the program to put data
  into the allocated memory.
• Named constant A memory location whose content
  is not allowed to change during program execution
• const double conversion 2.54
• const int noOfStudents 20
• const char blank
• Variable A memory location whose content may
  change during program execution.
• double amountDue
• int counter
• char ch
• int x, y
• string name
• assignment
• variable expression
• x 4
• y 4 5 11

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Declaring Variables

• 1. In C, all identifiers must be declared
  before they can be used. If we refer to an
  identifier without declaring it, the compiler
  will generate an error message indicating that
  the identifier is not declared.
• 2. A data type is called simple if the variable
  (or named constant) of that type can store only
  one value at a time. For example, if x is an,
  say, int variable. Then at a given time only one
  value can be stored in x.

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Putting Data into Variables

• In C there are two ways that data can be placed
  into a variable
• 1. Using Cs assignment statement, and
• 2. Use input (read) statements.

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Assignment Statement

• The assignment statement takes the form
• variable expression
• The expression is evaluated and its value is
  assigned to the variable on the left side.
• In C, is called the assignment operator.

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Input / Output

• Standard input (keyboard) cin
• cin gtgt variable gtgt variable
• int feet, inches
• cin gtgt feet gtgt inches
• Standard output (terminal) cout
• cout ltlt expression or manipulator ltlt expression
  or manipulator
• cout ltlt Hello there. ltlt endl

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Input (Read) Statement

• Syntax of cin together with gtgt
• cingtgtvariablegtgtvariable. . .
• In C, gtgt is called the extraction operator.
• Suppose miles is a variable of the type double.
• The statement
• cingtgtmiles
• causes the computer to get a value of the type
  double and place it in the memory cell miles.

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Input (Read) Statement

• By using more than one variable in cin, more than
  one value can be read at a time.
• Suppose feet and inch are variables of the type
  int. A statement like
• cingtgtfeetgtgtinch
• gets two integers (entered at the keyboard)
  and places them in the memory location feet and
  inch, respectively.

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Output

• The syntax of cout together with ltlt is
• coutltltexpression or manipulatorltltexpression or
  
• manipulator...
• In C, ltlt is called the insertion operator.
• expression (that is, expression) is evaluated and
  its value is printed at the current cursor
  position on the screen.
• manipulator manipulates the output. The simplest
  manipulator is endl (the last character is the
  letter el), which causes the cursor to move to
  the beginning of the next line.
• This is called an output statement. Sometimes
  this is also called a cout statement.
• In C, ltlt is called the stream insertion
  operator.
• Strings and expressions involving only one
  variable or a single value are evaluated to
  itself.

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Output

• The output of the C statement
• coutltlta
• is meaningful provided the variable a has been
  given a value. For example, the sequence of C
  statements,
• a 45
• coutltlta
• will produce an output of 45.

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Increment and Decrement Operators

• Frequent operation is to increment a count by 1
  (or decrement by 1)
• count count 1
• shorthand count
• count count 1
• count--
• Post-increment vs. pre-increment
• int count 5, res
• res count
• res count

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Preprocessor Directives

• Preprocessor directives are commands supplied to
  the preprocessor that cause the preprocessor to
  modify the text of a C program
• All preprocessor commands begin with
• including files
• include ltiostreamgt

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Preprocessor Directives

• Only a small number of operations are explicitly
  defined in C.
• Many of the functions and symbols that are
  necessary to run a C program are provided as a
  collection of libraries.
• Every library has a name and is referred as a
  header file. For example, the descriptions of the
  functions needed to perform I/O are contained in
  the header file iostream.
• The descriptions of some very useful mathematics
  functions such as power, absolute, sine, etc.,
  are contained in the header file cmath.
• Preprocessor directives are commands supplied to
  the preprocessor.
• All preprocessor commands begin with .
• There is no semicolon at the end of these
  commands since these are preprocessor commands
  not C commands.

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Preprocessor Directives

• The general syntax to include a header file
  (provided by the SDK) in a C program is
• include ltheaderFileNamegt
• The preprocessor directive
• include ltiostreamgt
• causes the preprocessor to include the header
  file iostream in the program.

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Preprocessor Directives

• In Standard C, header files have the file
  extension .h
• In Standsrd C, the descriptions of the
  functions needed to perform I/O are contained in
  the header file iostream.h
• include ltiostream.hgt
• include ltmath.hgt

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namespace

• Partitioning mechanism of namespace of standard
  variables
• for example header file iostream (among many
  others) declared in std namespace
• stdcin gtgt feet
• or
• using namespace std
• cin gtgt feet

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Creating a C Program

• A C program is a collection of functions, and
  one of the functions is the function main (which
  is executed first when program started).
• int main()
• statement1
• .
• .
• .
• statementn
• return 0
• Source code save in file with extension .cpp e.g.
  FirstProgram.cpp
• When program is compiled, the C compiler
  generates the object code .obj
• When object code is linked with the system
  resources an executable program is produced an
  usually saved with extension .exe

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Some Words about Program Style and Form

• First of all, program must be syntactically
  correct or it will not compile
• int x
• int y
• double z
• y w x
• Blanks separate tokens, you can use blank lines
  and spacing (indentation) to indicate program
  modules and structure
• All C statements must end with a semicolon (
  is called a statement terminator).
• Documentation The programs you write should be
  clear not only to you but others (me) who will
  read your code. Use comments to document
  concepts/procedures attempting to be realized by
  code
• / c-style multi-line comments /
• // C single line comments
• I like this document for a (well not too brief,
  but not bad) summary of good programming style
  and form
• C Programming Style Guidelines
• http//geosoft.no/development/cppstyle.html

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More on C I/O

• In C, I/O is (always) conceptualized as a
  stream of bytes, or a stream
• A stream is a sequence of characters from the
  source to the destination.
• Input stream A sequence of characters from an
  input device to the computer.
• Output stream A sequence of characters from the
  computer to an output device.
• Standard input (cin) and standard output (cout)

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Input predefined functions

• istreamVar.get(varChar)
• istreamVar.ignore(intExp, chExp)
• istreamVar.putback(ch)
• ch istreamVar.peek()

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Output and Formatting Output

• output stream manipulators
• cout ltlt setprecision(2)
• cout ltlt fixed cout.unsetf(iosfixed)
• cout ltlt scientific cout.unsetf(iosscientific)
• cout ltlt showpoint
• cout ltlt setw(5) ltlt x ltlt endl
• and many others

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File I/O

• File I/O is a five-step process
• Include the header file fstream in the program
• Declare file stream variables
• Associate the file stream variables with the
  input/output sources
• Use the file stream varaibles with gtgt, ltlt or
  other input/output functions
• Close the file

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File I/O

• include ltfstreamgt
• using namespace std
• int main()
• // Declare file stream variables such as the
  following
• ifstream inData
• ofstream outData
• // declare additional varaibles if any
• // Open files
• inData.open(a\\prog.dat)
• outData.open(a\\prog.out)
• // Code for data manipulation
• inData gtgt payRate
• outData ltlt The paycheck is ltlt pay ltlt endl

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Control Structures

• There are really only three main types of control
  structures in standard procedural programming
  languages
• Sequence steps are normally performed in a
  sequential manner
• Selection One of several actions is selected and
  executed (branch, other actions are not
  executed).
• Repetition One or more steps is performed
  repeatedly.

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Control Structures Sequence

• Normally in procedural programs, statements are
  executed in a sequential manner.
• selection and repetition control structures break
  up this sequential execution by introduction
  branch points and loops respectively
• Procedure/function calls also break up sequential
  execution to modularize algorithm into several
  small pieces

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Control Structures Selection

• Selection, or branch statements, chose one set of
  instructions among 2 or many to execute
  conditional on some test.
• In C selection control structures are
• if
• if else
• switch

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Relational and Boolean Operators

• C relational an boolean operators basis of
  conditional tests for selection control
  structures

Relational Operators
Logical (Boolean) Operators
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Selection if and if .. else

• if (expression)
• statement
• if (expression)
• statement1
• else
• statement2

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Compound (Block of) statements

• A compound statement groups a sequence of
  expressions
• if (age gt 18)
• cout ltlt Eligible to vote. ltlt endl
• cout ltlt No longer a minor. ltlt endl
• else
• cout ltlt Not eligible to vote. ltlt endl
• cout ltlt Still a minor. ltlt endl

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Multiple selections Nested if

• if (balance gt 50000.00)
• interestRate 0.07
• else if (balance gt 25000.00)
• interestRate 0.05
• else if (balance gt 1000.00)
• interestRate 0.03
• else
• interestRate 0.00

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Multiple Selections switch statements

• power to choose from among many alternatives
• switch (grade)
• case A
• cout ltlt The grade is A.
• break
• case B
• cout ltlt The grade is B.
• break
• case C
• cout ltlt The grade is C.
• break
• case D
• cout ltlt The grade is D.
• break
• case F
• cout ltlt The grade is F.
• break

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Control Structures Repetition

• Repetition is a common activity in algorithms,
  and very powerful
• Repetition is another way in which we get away
  from the simple sequential execution of a
  sequence of statements
• C looping structures
• while
• for

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While looping structure

• while (expression)
• statement
• i 0
• while (i lt 20)
• cout ltlt i ltlt
• i i 5
• cout ltlt endl

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While looping structure
flag-controlled found false while
(!found) if (expression) found
true EOF-controlled cin gtgt variable while
(cin) cin gtgt variable

• counter-controlled
• counter 0
• while (counter lt N)
• counter
• sentinel-controlled
• cin gtgt variable
• while (variable ! sentinel)
• cin gtgt variable

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for looping structure

• while loop is general enough to implement most
  (all?) forms of repetition
• for loop is a specialized form to simplify
  writing of count-controlled loops (since they are
  so common).

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for looping structure

• for (initial statement loop condition update
  statement)
• statement
• for (i1 ilt5 i)
• cout ltlt Hello! ltlt endl
• cout ltlt ltlt endl

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Break and Continue

• break
• exit early from a loop
• skip the remainder of the switch structure
• continue
• skips remaining statements in the loop and
  proceeds with the next iteration of the loop

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Functions

• A C Program (or any program in a procedural
  programming language)
• Collection of 1 or more subprograms called
  functions
• Which is a collection of statements that can
  accomplish something useful
• sequence, selection, repetition
• Special function called main

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Predefined Functions
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Using Predefined Functions

• Include the header file that contains the
  functions specification
• Call function with correct arguments
• Possibly handle errors returned as codes or
  otherwise

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Example 6-1 // How to use predefined
functions. include ltiostreamgt include
ltcmathgt include ltcctypegt include
ltcstdlibgt using namespace std int main() int
x double u,v coutltlt"Line 1 Uppercase a
is " ltltstatic_castltchargt(toupper('a'))
ltltendl //Line 1 u 4.2 //Line
2 v 3.0 //Line 3 coutltlt"Line 4 "ltltultlt"
to the power of " ltltvltlt"
"ltltpow(u,v)ltltendl //Line 4 coutltlt"Line 5 5
to the power of 4 " ltltpow(5,4)ltltendl
//Line 5
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Example 6-1 // How to use predefined
functions. include ltiostreamgt include
ltcmathgt include ltcctypegt include
ltcstdlibgt using namespace std int main() int
x double u,v coutltlt"Line 1 Uppercase a
is " ltltstatic_castltchargt(toupper('a'))
ltltendl //Line 1 u 4.2 //Line
2 v 3.0 //Line 3 coutltlt"Line 4 "ltltultlt"
to the power of " ltltvltlt"
"ltltpow(u,v)ltltendl //Line 4 coutltlt"Line 5 5
to the power of 4 " ltltpow(5,4)ltltendl
//Line 5
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User-Defined Functions

• To solve a problem you must learn to write your
  own functions
• User-defined functions in C are classified into
  two categories
• Functions that have a data type, called
  value-returning functions
• Functions that do not have a data type, called
  void functions.

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Value-Returning Functions

• functionType functionName(formal parameter List)
• statements
• return value
• int min(int number1, int number2)
• if (number1 lt number2)
• return number1
• else
• return number2

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Value-Returning Functions

• Once a value-returning function computes the
  value, the function returns this value via the
  return statement.
• When a return statement executes in a function,
  the function immediately terminates and returns
  control back to the caller.
• A value-returning function must return a value,
  therefore it must have at least 1 return
  statement somewhere in it.

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Non Value-Returning Functions

• called void functions
• void functionName(formal parameter List)
• statements
• void printStars()
• cout lt ltlt end
• cout lt ltlt end

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Reference Parameters

• Normal simple data type parameters in C and C
  are passed by value.
• Sometimes it is useful to pass in parameters by
  reference.
• When you want to return more than one value from
  a function.
• When the value of the actual parameter needs to
  be changed.
• When passing the address would save memory space
  and time relative to copying a large amount of
  data.

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Reference Parameters

• Value parameter A formal parameter that receives
  a copy of the content of the corresponding actual
  parameter.
• Reference parameter A formal parameter that
  receives the location (memory address) of the
  corresponding actual parameter.

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Reference Parameters

• int main()
• int courseScore
• cout ltlt This program computes the course
  grade.
• ltlt endl
• getScore(courseScore)
• printGrade(courseScore)
• return 0
• void getScore(int score)
• cout ltlt Enter the course score
• cin gtgt score
• cout ltlt endl ltlt Course score is ltlt score ltlt
  endl

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Scope of Identifiers in C

• Identifier A C identifier consists of letters,
  digits, and the under score character (_), and
  must begin with a letter or underscore.
• C is case sensitiveuppercase and lower case
  letters are different.
• Some of the predefined identifiers are cout and
  cin.
• Unlike reserved words, pre-defined identifiers
  may be redefined, but it would not be wise to do
  so.
• Identifiers are used to name user-defined
  variables, constants, functions, structures and
  classes, for example.
• Q Are you allowed to access any identifier
  anywhere in the program?

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Scope of Identifiers in C

• Q Are you allowed to access any identifier
  anywhere in the program?
• A No, certain rules exist that you must follow
  (an know) to access an identifier.
• The scope of an identifier refers to where in the
  program an identifier is accessible.

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Scope of Identifiers in C

• Local identifier Identifiers declared within a
  function (or block).
• Global identifier Identifiers declared outside
  of every function definition.

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Scope of Identifiers in C

• In general, the following rules apply when an
  identifier is accessed.
• Global identifiers (such as variables) are
  accessible by a function or a block if
• The identifier is declared before the function
  definition (block),
• The function name is different from the
  identifier,
• All parameters of the function have names
  different than the name of the identifier, and
• All local identifiers (such as local variables)
  have names different than the name of the
  identifier.
• (Nested Block) An identifier declared within a
  block is accessible
• Only within the block from the point at which it
  is declared until the end of the block, and
• By those blocks that are nested within that block
  if the nested block does not have an identifier
  with the same name as that of the outside block
  (the block that encloses the nested block.)
• The scope of a function name is similar to the
  scope of an identifier declared outside any
  block. That is, the scope of a function name is
  the same as the scope of a global variable.

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• include ltiostreamgt
• using namespace std
• const double rate 10.50
• int z
• double t
• void one(int x, char y)
• void two(int a, int b, char x)
• void three(int one, double y, int z)
• int main ()
• int num, first
• double x, y, z
• char name, last
• .
• .
• .

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• void one(int x, char y)
• .
• .
• .
• int w
• void two(int a, int b, char x)
• int count
• .
• .
• .

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• void three(int one, double y, int z)
• char ch
• int a
• .
• .
• .
• //Block four
• int x
• char a
• .
• .
• //end Block four
• .
• .
• .

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Static and Automatic Variables

• The variables dicussed so far have followed two
  simple rules
• Memory for global variables remains allocated as
  long as the program executes.
• Memory for a variable declared within a block is
  allocated at block entry and deallocated at block
  exit. For example, memory for the formal
  parameters and local variables of a function is
  allocated when the function is called and
  deallocated when the function exits.

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Static and Automatic Variables

• A variable for which memory is allocated at block
  entry and deallocated at block exit is called an
  automatic variable.
• A variable for which memory remains allocated as
  long as the program executes is called a static
  variable.
• Global variables are static variables and, by
  default, variables declared within a block are
  automatic variables.
• You can declare a static variable within a block
  by using the reserved word static.

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• Example 7-9
• //Program Static and automatic variables
• include ltiostreamgt
• using namespace std
• void test()
• int main()
• int count
• for(count 1 count lt 5 count)
• test()
• return 0

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• void test()
• static int x 0
• int y 10
• x x 2
• y y 1
• coutltlt"Inside test x "ltltxltlt" and y "
• ltlty ltltendl
• Output
• Inside test x 2 and y 11
• Inside test x 4 and y 11
• Inside test x 6 and y 11
• Inside test x 8 and y 11
• Inside test x 10 and y 11

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User-Defined Simple Data Types

• Recall the following categories of data types in
  C
• We now look to simple mechanisms for producing
  user-defined data types

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Enumeration Type

• A data type is a set of values together with a
  set of operations on those values.
• In order to define a new simple data type, called
  enumeration type, we need three things
• A name for the data type.
• A set of values for the data type.
• A set of operations on the values.
• C allows the user to define a new simple data
  type by specifying its name and the values, but
  not the operations.
• The values that we specify for the data type must
  be identifiers.

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• The syntax for enumeration type is
• enum typeNamevalue1, value2, ...
• where value1, value2, are identifiers.
• value1, value2, are called enumerators.
• value1 lt value2 lt value3 lt...
• In C, enum is a reserved word.
• Enumeration type is an ordered set of values.

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• Example 8-1
• enum colorsbrown, blue, red, green, yellow
• defines a new data type, called colors
• The values belonging to this data type are brown,
  blue, red, green, and yellow.
• Example 8-2
• enum standingfreshman, sophomore, junior,
  senior
• defines standing to be an enumeration type.
• The values belonging to standing are freshman,
  sophomore, junior, and senior.

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• Example 8-3
• The following are illegal enumeration types
  because none of the values is an identifier.
• //Illegal enumeration types
• enum grades'A', 'B', 'C', 'D', 'F'
• enum places1st, 2nd, 3rd, 4th
• The following are legal enumeration types
• enum gradesA, B, C, D, F
• enum placesfirst, second, third, fourth

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• If a value has already been used in one
  enumeration type, it cannot be used by any other
  enumeration type in the same block.
• The same rules apply to enumeration types
  declared outside of any blocks.
• Example 8-4
• enum mathStudentJohn, Bill, Cindy, Lisa, Ron
• enum compStudentSusan, Cathy, John, William
  //Illegal
• Suppose that these statements are in the same
  program in the same block.
• The second enumeration type, compStudent, is not
  allowed because the value John was used in the
  previous enumeration type mathStudent.

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• Declaring Variables
• The syntax for declaring variables is the same as
  before, that is,
• dataType identifier, identifier,...
• The following statement defines an enumeration
  type sports
• enum sportsbasketball, football, hockey,
• baseball, soccer,volleyball
• The following statement declares variables of the
  type sports.
• sports popularSport, mySport

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Next Class

• Quiz 1 Over review material
• Data Types
• simple, structured
• declaring
• Control Structures
• sequence, selection (if/then, case) and
  repetition (while, for)
• functions
• declaring, parameters, return values
• I/O

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Next Class

• 1 Dimensional Arrays and C-strings (Ch 9)
• Ch9 405-430 (1ed) 423-450 (2ed)
• Active Reading
• I agree ?
• I disagree X
• Thats new
• Thats important !
• I wonder ?
• I dont understand ??
• Prepare 2 cards
• The most important point of the reading
  assignment
• The biggest question or thing you didnt
  understand in the reading assignment.