Learning C++ - Pointers in c++ 2

Learning C++ - Pointers in c++ 2

• 1.
  Pointers 1
• 2.
  Section Outline • Introductionto Memory • Pointers • Arrays • Scope 2
• 3.
  Section Outline • Introductionto Memory • Pointers • Arrays • Scope 3
• 4.
  Introduction to Memory •Problems related to pointer in C++ Arrays Function’s return Importance of working with memories 4 Memory space (a cell) that has a value . . 1000 1001 1002 . . A Pointer
• 5.
  Introduction to Memory •More Details: 5 Memory space (a cell) that has a value . . 1000 1001 1002 . . A Pointer 0 1 1 0 1 0 0 1
• 6.
  Section Outline • Introductionto Memory • Pointers • Arrays • Scope 6
• 7.
  (this type canaccept any type in assignment but when we want to assignment to other variable we must do a cast) • Definition of a Pointer in C++ Type * Name = NULL; (it means ptrName points to nowhere , defines in <iostream.h>) e.g. int * ptr1; void * ptr2 Pointers 7 Why initialization is important?
• 8.
  • e.g. int main() { voidvar1; var1 = ‘A’; var1 = 1.322; float var2 = ( float ) var1; } Pointers 8
• 9.
  • Note : –& has two means in two case • Address fetch int var1 ; cout << & var1; • In calling function – * has two means in two case • In definition of a variable, near the type means we are defining a pointer • Otherwise ,as a operator , get the value of a pointer int a = 23; int * pointer = a; cout << *pointer; Pointers 9 Out put : 23
• 10.
  • Notice tothis code: void main() { int var1 = 25; int * var2 = & var1; cout<<var1<<“n”<<var2<<“n”<<*var2; } Output: 25 0x9934344 25 Pointers(cont.) 10 Return address
• 11.
  Pointers(cont.) • Pointer`s access inta; int *ptr = a; * ptr = 20; *(ptr+1) = 23; ptr++; 11 20 23 XXXXXXXX (1) 1001: ptr (2) 1002: ptr (3) 1003: ptr
• 12.
  Section Outline • Introductionto Memory • Pointers • Arrays • Scope 12
• 13.
  • Definition ofan array (literature) • Dimension o1D: has been exampled latter o2D : arrangement in memory 13 1001 1002 1003 0 3 6 1 4 8 2 5 7 Arrays In C++ In Fortran
• 14.
  Arrays(cont.) • What isrelated between array and pointers: i. Definition of an array in C++ ii. Array`s name iii. Combining array and pointer concepts iv. Array`s bound 14
• 15.
  i. Definition ofan array in C++ type Name[dimensions]; int Ar_name[5]; int Ar_name[10][20]; Note : if we define an array with 5 cell then C++ count them from zero. (for , while, do while)  First things in C++ usually has the zero number. 15 Cell No. 0 Cell No. 1 Cell No. 2 Cell No. 3 Arrays(cont.)
• 16.
  ii. Array`s name! array`s name has the address of the first cell in the memory. int myArray[5]; int * myPtr = myArray; int myArray[5]; int counter = 0; int counter = 0; for(; counter< 5; counter++) for(; counter< 5; counter++) { { } } 16 myArray[counter] = counter; myPtr[counter] = counter; Arrays(cont.)
• 17.
  iii. Combining arrayand pointer concepts define a pointer : int ptr[]; iv. Array`s bound  In C++ we must be cautious about array boundaries(otherwise a Exception appear) 17 0 1 2 1000(my_array) 1001 1002(my_array+2) ????? Arrays(cont.)
• 18.
  • Initializing array It`s related to use to initializing an array or not , but it`s better to initialize arrays, specially in calculation cases  How to initialize an array » int numbers[4] = {1, 3, 708, -12}; » float floats[3][2] = {{1.0,5.0},{0.5,3.1},{6,0.15}}; » char myArray [5] = {‘A’,’b’,’E’,’d’,’q’}; » Do this in a loop by initialize each after another int myArray[10][5]; for(int i=0; i<10; i++) for(int j=0; i<5; j++) myArray[i][j] = 0; 18 Every where in C++ we can define a variable At some commands such as for, if, while, do while the line just after them do not need { } (or the first command after these has impressed by themselves) Arrays(cont.)
• 19.
  • Note:accolade int myArray[5];int myArray[5]; int counter = 0; int counter = 0; for(; counter< 5; counter++) for(; counter< 5; counter++) { } 19 myArray[counter] = counter; myPtr[counter] = counter; A = B+1; Arrays(cont.)
• 20.
  Section Outline • Introductionto Memory • Pointers • Arrays • Scope 20
• 21.
  Scope • Every variablecan just appear and use exactly in a deterministic area that named “scope” . • This rules over all the variable , even pointers e.g. int i = 0; if(myVar != 1) { int i = 123; } cout << i; 21 Out put is : 0
• 22.
  In future : i.Functions ii. Class and related concepts iii.ERRORS 22