CISC105

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CISC105 General Computer Science

• Class 7 06/26/2006

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What we should know about writing Programs in C

• Structure of a Program
• Preprocessor Directives (include, define)
• Variable Types
• int, double, char
• Input/Output Functions
• scanf, printf (formatting Output)
• Variable Manipulation
• Order of Operation
• Parenthesis, Function Calls, (! - ) Unary
  Operators, / , - ,lt lt gt gt, !, , ,
  

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What we should know about writing Programs in C

• Functions
• Declaration, Definition, Use
• Selection Structures
• if, ifelse, Nested if
• Repetition Structures
• while, dowhile, for, Nested Loops

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How memory works in programs

• Memory
• Address Location in memory
• Content what is in the location
• Amount Used depends on the type of Variable
• Program
• Main Function
• Variables
• Arguments, Formal Parameters and Functions

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Functions and Memory

• We have learned that arguments provide a link
  between functions
• Functions run in separate memory with separate
  values
• The operator returns the memory address of a
  variable
• Example pointer.1.c and pointer.1.1.c

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Pointers

• We can declare a variable that contains the
  memory address of another variable.
• To declare a pointer we declare using an
• int y - declare a variable y that contains the
  address of an integer
• y can only be set to the address of an integery
  x
• To access the value at memory location pointed to
  by y you need to use an printf(Value of
  contents at location pointed to by y is d, y)
• See example pointer.2.c

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Function Call by Value

• We have learned that when we call a function and
  pass and argument the argument value is not
  changed in the main function.
• See Example pointer.3.c

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Function Call by Reference

• By using pointers and passing memory address as
  arguments we can change the values in the calling
  function.
• See example pointer.4.c

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Three Uses of Operator

• Multiplication Operator (a b c )
• Pointer Declaration (int y )
• Follow the pointer ( y 200 )
• See example pointer.5.c

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Passing Input/Output in a single Function

• You can pass arguments by reference that act as
  input output (Example pointer.6.c)
• You can call functions multiple time by passing
  different variables by reference as input
  output (Example pointer.7.c)

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Scope of Variables

• Scope of a name is the region in a program where
  a particular meaning of a name is valid
• Global available to every function in the
  program
• Local available only within the function where
  it is declared
• Overridden a global variable name can be
  inaccessible to a function if a variable of the
  same name is declared locally