CS101 Slides

1
Header files
Lab 9, Lab 10, Lab 11 and Assignment 2
2
Header files
myArray.h
// declaration class myArray private int
data public myArray(int size) myArray()

myArray.cpp
// declaration class myArray private int
data public myArray(int size) myArray()
// implementation myArraymyArray(int size)
data new intsize myArraymyArray()
delete data
Break into 2 files
myArray.cpp
// implementation myArraymyArray(int size)
data new intsize myArraymyArray()
delete data
3
Include statement

• The declarations are stored in the header file
• The header file has the same name as the original
  file, but the extension is .h instead of .cpp
  (eg. myArray.h)
• Only the implementation code is stored in the
  .cpp file.
• But we still need the declarations!
• We must include the declarations in the .cpp file

4
Include statement (example)
myArray.cpp
// declaration class myArray private int
data public myArray(int size) myArray()
// implementation myArraymyArray(int size)
data new intsize myArraymyArray()
delete data
myArray.cpp
include myArray.h // implementation myArraym
yArray(int size) data new intsize myArr
aymyArray() delete data
The include statement instructs the compiler to
get the declarations from the header file
5
Separate file for main()

• The global functions, like main(), must go to a
  separate .cpp file (eg. program.cpp)
• Include myArray.h, if you want to use a myArray
  object
• program.cpp, myArray.cpp and myArray.h must be in
  the same project!!!

// standard library file, uses lt gt include
ltiostream.hgt // user defined file, uses
include myArray.h void func(myArray ary)
cout ltlt using ary\n // do something
with ary void main() myArray ary(10)
func(ary)
program.cpp
6
Include myArrya.h
myArray.h
myArray.cpp
ifndef MYARRAY_H define MYARRAY_H //
declaration class myArray private int
data public myArray(int size) myArray()
endif
include myArray.h // implementation myArraym
yArray(int size) data new intsize
myArraymyArray() delete data
myArray.h is included in program.cpp as well as
myArray.cpp, need to indicate and avoid
duplication by ifndef MYARRAY_H, define
MYARRAY_H and endif in myArray.h