C Fundamentals

1
C Fundamentals

• CS-240
• Dick Steflik

2
Primitive Types

• Integer types
• char 8 bit
• short 16 bit
• int 32 bit
• long 64 bit
• Real Types
• float - 32 bit real numbers
• double - 64 bit real numbers

3
Constants

• In Java constants are variables that are never
  allowed to change value
• public static final int abc 100
• In C constants are defined as
• const int abc 100 const char plus
• constants are resolved by the compiler
  preprocessor by doing text substitutions of the
  value for all occurrences of the name.

4
Boolean (false/true)

• C has no boolean type like Java
• the value 0 represents false
• any other value represents true
• the statement if (50) cout ltltt
• will always print t as 50 is not 0 so the
  predicate is true
• the statement if (5-5) coutltltt else cout ltlt
  f
• will always print f as (5-5) is 0 (i.e. False)
  

5
Strings

• C has no built-in String type like Java
• Strings are implemented as null terminated arrays
  of characters.
• char 3 abc me
• array abc consists of m, e, null
• abc me (shortcut for defining and
  initializing a string)
• string functions are in ltstring.hgt

6
Derived Types

• These operators create new types from the basic
  types
• pointer to
• const constant pointer
• reference to (addressing operator)
• vector of
• () function returning

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Null statements

• the simplest statement is the null statement
• useful if the syntax requires a statement
• for instance to introduce a time delay into a
  program
• for (int j 0 j lt 100 j)

8
C Program Structure

• A C Program consists a set of file(s)
  consisting of declarations of
• types
• functions
• variables
• constants

9
externalization

• To use a name to refer to the same thing in two
  different source files it must be defined as
  external
• extern double sqrt(double)
• extern istream cin
• extern int abcd

10
Header files

• To guarantee consistency between source files
  externalize definitions into header (.h) files
• for instance math.h contains the externalized
  definitions for interfacing to the mathematic
  system utilities.
• To use the functions in math.h include math.h in
  your source file
• include ltmath.hgt

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Header files (cont.)

• math.h is provided as part of C but you can
  make your own header files
• to include your own header file, place it in the
  same directory as the files to use it and in each
  source file place the line
• include myfile.h
• note the instead if lt gt, use lt gt to include
  from the standard include directory use to
  include from elsewhere (full path)

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Example
header.h
main.cpp
extern char prog_name extern void f( )
include header.h char prog_name
silly, but complete main() f()
f.cpp
include ltiostream.hgt include header.h void
f() cout ltlt prog_name ltlt \n
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