1. 1 CSC 211 Data Structures Lecture 5 Dr. Iftikhar Azim Niaz ianiaz@comsats.edu.pk 1

2. 2 Last Lecture Summary Data type and Data structure Data types in C Arrays  Declaration  Initialization  Representation  Operations  Arrays and functions Pointers  Declaration, Initialization  Arrays and pointers 2

3. 3 Objectives Overview Concept of Pointer Pointer operators  Address and Indirection Pointer Arithmetic Pointer and functions  Pass by Value  Pass by Reference Pointer and Arrays

4. 4 Pointers Powerful, but difficult to master Simulate call-by-reference Close relationship with arrays and strings A pointer, like an integer, holds a number  Interpreted as the address of another object Must be declared with its associated type:  e.g., “pointer to integer”, “pointer to character”, etc.  int *x; Useful for:  Dynamic objects

5. 5 Pointer Indirection Accessing an object through a pointer is called indirection The “address-of” operator ( & )obtains an object’s address The “de-referencing” operator (*) refers to the object the pointer pointed at

6. 6 Pointer Diagram int i = 8; // declaring integer variable int *ip; // declaring pointer variable ip = &i; // assigning address of i to ip cout<<*ip; // output value pointed to by ip Pointer VariableInteger Variable

7. 7 Pointer Variable Declarations and Initialization Pointer variables  Contain memory addresses as their values  Normal variables contain a specific value (direct reference)  Pointers contain address of a variable that has a specific value (indirect reference)  Indirection – referencing a pointer value count7 7 countPtr

8. 8 Pointer Variable Declarations and Initialization Pointer declarations  * used with pointer variables int *myPtr;  Declares a pointer to an int (pointer of type int * )  Multiple pointers require using a * before each variable declaration int *myPtr1, *myPtr2;  Can declare pointers to any data type  Initialize pointers to 0, NULL, or an address 0 or NULL – points to nothing ( NULL preferred)

9. 9 Pointer Operators & (address operator)  Returns address of operand int y = 5; int *yPtr; yPtr = &y; // yPtr gets address of y yPtr “points to” y yPtr y 5 yptr 500000 600000 y 5 Address of y is value of yptr

10. 10 Pointer Operators * (indirection/dereferencing operator)  Returns a synonym/alias of what its operand points to  *yptr returns y (because yptr points to y )  * can be used for assignment Returns alias to an object *yptr = 7; // changes y to 7  Dereferenced pointer (operand of * ) must be an lvalue (no constants) * and & are inverses  They cancel each other out

11. 11 void main(void) { int x, y; int *p, *q; p = &x; q = &y; *p = 2; y = *p; *q = *p; p = q; x y p q Pointer Example

12. 12 void main(void) { int x, y; int *p, *q; p = &x; q = &y; *p = 2; y = *p; *q = *p; p = q; x y p q Pointer Example (cont..)

13. 13 void main(void) { int x, y; int *p, *q; p = &x; q = &y; *p = 2; y = *p; *q = *p; p = q; x y p q Pointer Example (cont..)

14. 14 void main(void) { int x, y; int *p, *q; p = &x; q = &y; *p = 2; y = *p; *q = *p; p = q; 2 x y p q Pointer Example (cont..)

15. 15 void main(void) { int x, y; int *p, *q; p = &x; q = &y; *p = 2; y = *p; *q = *p; p = q; 2 2 x y p q Pointer Example (cont..)

16. 16 Pointer Declaration Examples double * p1; double* p2;  // think p2 is of type "double*“ double *p3;  // think *p3 is a double double x = 4.5; p1 = &x;  // p1 holds the memory address of x int * q1;  // q1 can hold the memory address of ints only q1 = &x;  // error - x is a double, q1 only works with int int m = 4; q1 = &m;  // legal - types match

17. 17 Pointer Example int x=3,y=4,z=5,*xp,*yp,*zp; xp=&z; // xp holds the address of z yp=&(*xp); // yp points the pointer variable xp zp=&(*yp); // zp points the pointer variable yp so all the pointers xp, yp and zp point to z cout<<"value in z...."<<z;cout<<"\n value in *yp......"<<*yp; cout<<"\n value in *xp......"<<*xp;cout<<"\n valuein *zp...."<<*zp; *yp=x ; //now when we change pointer variable yp it will change the value of z; cout<<"\n\n value in z...."<<z;cout<<"\n value in *yp......"<<*yp; cout<<"\n value in *xp......"<<*xp;cout<<"\n valuein *zp...."<<*zp; *zp=1; //zp also points z directly or indirectly so it will //also change value of z’ cout<<"\n \n value in z...."<<z; cout<<"\n value in *yp......"<<*yp; cout<<"\n value in *xp......"<<*xp; cout<<"\n valuein *zp...."<<*zp; Output (5,3,1)

18. 1. Declare variables 2 Initialize variables 3. Print Program Output 1/* Fig. 7.4: fig07_04.c 2 Using the & and * operators */ 3#include 3#include 4 5int main() 6{6{6{6{ 7 int a; /* a is an integer */ 8 int *aPtr; /* aPtr is a pointer to an integer */ 9 10 a = 7; 11 aPtr = &a; /* aPtr set to address of a */ 12 13 printf( "The address of a is %p" 14 "\nThe value of aPtr is %p", &a, aPtr ); 15 16 printf( "\n\nThe value of a is %d" 17 "\nThe value of *aPtr is %d", a, *aPtr ); 18 19 printf( "\n\nShowing that * and & are inverses of " 20 "each other.\n&*aPtr = %p" 21 "\n*&aPtr = %p\n", &*aPtr, *&aPtr ); 22 23 return 0; 24} The address of a is 0012FF88 The value of aPtr is 0012FF88 The value of a is 7 The value of *aPtr is 7 Proving that * and & are complements of each other. &*aPtr = 0012FF88 *&aPtr = 0012FF88 The address of a is the value of aPtr. The * operator returns an alias to what its operand points to. aPtr points to a, so *aPtr returns a. Notice how * and & are inverses

19. 19 Review of pointers A pointer is just a memory location. A memory location is simply an integer value, that we interpret as an address in memory. The contents at a particular memory location are just a collection of bits – there’s nothing special about them that makes them int s, char s, etc.  How you want to interpret the bits is up to you.  Is this... an int value?... a pointer to a memory address?... a series of char values? 0xfe4a10c5

20. 20 Review of pointer variables A pointer variable is just a variable, that contains a value that we interpret as a memory address. Just like an uninitialized int variable holds some arbitrary “garbage” value, an uninitialized pointer variable points to some arbitrary “garbage address” char *m; (char *) m

21. 21 Following a “garbage” pointer What will happen? Depends on what the arbitrary memory address is:  If it’s an address to memory that the OS has not allocated to our program, we get a segmentation fault  If it’s a nonexistent address, we get a bus error  Some systems require multibyte data items, like int s, to be aligned: for instance, an int may have to start at an even-numbered address, or an address that’s a multiple of 4. If our access violates a restriction like this, we get a bus error  If we’re really unlucky, we’ll access memory that is allocated for our program – We can then proceed to destroy our own data!

22. 22 Testing whether a pointer points to something meaningful? There is a special pointer value NULL, that signifies “pointing to nothing”. You can also use the value 0. char *m = NULL;... if (m) {... safe to follow the pointer... } Here, m is used as a Boolean value  If m is “false”, aka 0, aka NULL, it is not pointing to anything  Otherwise, it is (presumably) pointing to something good  Note: It is up to the programmer to assign NULL values when necessary

23. 23 Indirection operator * Moves from address to contents char*m = ″ dog ″ ; char result = *m; m gives an address of a char *m instructs us to take the contents of that address result gets the value ′ d ′ (char *) m d(char)o(char)g(char)NUL(char) (char) result d(char)

24. 24 Address operator & Instead of contents, returns the address char*m = ″ dog ″, **pm = &m; pm needs a value of type char ** Can we give it *m ? No – type is char Can we give it m ? No – type is char * &m gives it the right value – the address of a char * value (char *) (char **) m pm d(char)o(char)g(char)NUL(char)

25. 25 Pointer arithmetic C allows pointer values to be incremented by integer values char*m = ″ dog ″ ; char result = *(m + 1); m gives an address of a char (m + 1) gives the char one byte higher *(m + 1) instructs us to take the contents of that address result gets the value ′ o ′ (char *) m d(char)o(char)g(char)NUL(char) (char) result o(char)

26. 26 Pointer arithmetic A slightly more complex example: char*m = ″ dog ″ ; char result = *++m; m gives an address of a char ++m changes m, to the address one byte higher, and returns the new address *++m instructs us to take the contents of that location result gets the value ′ o ′ (char *) m d(char)o(char)g(char)NUL(char) (char) result o(char)

27. 27 Pointer arithmetic How about multibyte values?  Q: Each char value occupies exactly one byte, so obviously incrementing the pointer by one takes you to a new char value... But what about types like int that span more than one byte?  A: C “does the right thing”: increments the pointer by the size of one int value inta[2] = {17, 42}; int *m = a; int result = *++m; (int *) m (char) result 42(int) 17(int)42(int)

28. 28 Pointer Expressions and Pointer Arithmetic Arithmetic operations can be performed on pointers  Increment/decrement pointer ( ++ or -- )  Add an integer to a pointer( + or +=, - or -= )  Pointers may be subtracted from each other  Operations meaningless unless performed on an array

29. 29 Pointer Expressions and Pointer Arithmetic 5 element int array on machine with 4 byte int s  vPtr points to first element v[ 0 ] at location 3000 ( vPtr = 3000 )  vPtr += 2; sets vPtr to 3008 vPtr points to v[ 2 ] (incremented by 2), but the machine has 4 byte int s, so it points to address 3008 pointer variable vPtr v[0]v[1]v[2]v[4]v[3] 30003004300830123016location

30. 30 Pointer Expressions and Pointer Arithmetic Subtracting pointers  Returns number of elements from one to the other. If vPtr2 = v[ 2 ]; vPtr = v[ 0 ];  vPtr2 - vPtr would produce 2 Pointer comparison ( )  See which pointer points to the higher numbered array element  Also, see if a pointer points to 0

31. 31 Pointer Expressions and Pointer Arithmetic Pointers of the same type can be assigned to each other  If not the same type, a cast operator must be used  Exception: pointer to void (type void * ) Generic pointer, represents any type No casting needed to convert a pointer to void pointer void pointers cannot be dereferenced

32. 32 Pointers to Functions Pointer to function  Contains address of function  Similar to how array name is address of first element  Function name is starting address of code that defines function Function pointers can be  Passed to functions  Stored in arrays  Assigned to other function pointers

33. 33 Pointers to Functions Example: bubblesort  Function bubble takes a function pointer bubble calls this helper function this determines ascending or descending sorting  The argument in bubblesort for the function pointer: bool ( *compare )( int, int ) tells bubblesort to expect a pointer to a function that takes two ints and returns a bool  If the parentheses were left out: bool *compare( int, int ) Declares a function that receives two integers and returns a pointer to a bool

34. 1. Initialize array 2. Prompt for ascending or descending sorting 2.1 Put appropriate function pointer into bubblesort 2.2 Call bubble 3. Print results 1/* Fig. 7.26: fig07_26.c 2 Multipurpose sorting program using function pointers */ 3#include 4#define SIZE 10 5void bubble( int [], const int, int (*)( int, int ) ); 6int ascending( int, int ); 7int descending( int, int ); 8 9int main() 10{ 11 12 int order, 13 counter, 14 a[ SIZE ] = { 2, 6, 4, 8, 10, 12, 89, 68, 45, 37 }; 15 16 printf( "Enter 1 to sort in ascending order,\n" 17 "Enter 2 to sort in descending order: " ); 18 scanf( "%d", &order ); 19 printf( "\nData items in original order\n" ); 20 21 for ( counter = 0; counter < SIZE; counter++ ) 22 printf( "%5d", a[ counter ] ); 23 24 if ( order == 1 ) { 25 bubble( a, SIZE, ascending ); 26 printf( "\nData items in ascending order\n" ); 27 } 28 else { 29 bubble( a, SIZE, descending ); 30 printf( "\nData items in descending order\n" ); 31 } 32 Notice the function pointer parameter.

35. 3.1 Define functions 33 for ( counter = 0; counter < SIZE; counter++ ) 34 printf( "%5d", a[ counter ] ); 35 36 printf( "\n" ); 37 38 return 0; 39} 40 41void bubble( int work[], const int size, 42 int (*compare)( int, int ) ) 43{ 44 int pass, count; 45 46 void swap( int *, int * ); 47 48 for ( pass = 1; pass < size; pass++ ) 49 50 for ( count = 0; count < size - 1; count++ ) 51 52 if ( (*compare)( work[ count ], work[ count + 1 ] ) ) 53 swap( &work[ count ], &work[ count + 1 ] ); 54} 55 56void swap( int *element1Ptr, int *element2Ptr ) 57{ 58 int temp; 59 60 temp = *element1Ptr; 61 *element1Ptr = *element2Ptr; 62 *element2Ptr = temp; 63} 64 ascending and descending return true or false. bubble calls swap if the function call returns true. Notice how function pointers are called using the dereferencing operator. The * is not required, but emphasizes that compare is a function pointer and not a function.

36. 3.1 Define functions Program Output 65int ascending( int a, int b ) 66{ 67 return b < a; /* swap if b is less than a */ 68} 69 70int descending( int a, int b ) 71{ 72 return b > a; /* swap if b is greater than a */ 73} Enter 1 to sort in ascending order, Enter 2 to sort in descending order: 1 Data items in original order 2 6 4 8 10 12 89 68 45 37 Data items in ascending order 2 4 6 8 10 12 37 45 68 89 Enter 1 to sort in ascending order, Enter 2 to sort in descending order: 2 Data items in original order 2 6 4 8 10 12 89 68 45 37 Data items in descending order 89 68 45 37 12 10 8 6 4 2

37. 37 Reference Semantics Pass/call by reference  When a function parameter is passed as a pointer  Changing the parameter changes the original argument  Arrays are pointers Arrays as ArgumentsArrays as Arguments  structs are usually passed as pointers

38. 38 Pass by value void by_value(int a, int b, int c); void main() { int x = 2, y = 4, z = 6; cout<<"\nBefore calling by_value(), x y z "<<x<<y<<z; by_value(x, y, z); cout<<"\nAfter calling by_value(), x, y, z "<<x<<y<<z; } void by_value(int a, int b, int c) { a = 0; b = 0; c = 0; }

39. 39 void by_ref(int *a, int *b, int *c); void main(){ int x = 2, y = 4, z = 6; by_ref(&x, &y, &z); //Passing address of x,y and z; cout<<"\nAfter calling by_ref(), x, y, z = "<<x<<y<<z; } void by_ref(int *a, int *b, int *c) //*a holds the value at address &x { *a = 0; //will change the value at the address of x *b = 0; //will change the value at the address of y *c = 0; //will change the value at the address of z }

40. 40 Example: initializing an array #define N_VALUES 5 float values[N_VALUES]; float *vp; for ( vp = &values[0]; vp < &values[N_VALUES]; ) *vp++ = 0; (float *) vp (float)(float)(float)(float)(float) &values[0] &values[N_VALUES] values (float []) 0(float)0(float)0(float)0(float)0(float) (done!)

41. 41 A note on assignment: Rvalues vs. Lvalues What’s really going on in an assignment?  Different things happen on either side of the = int a = 17, b = 42; b = a; 17(int) a 42(int) b a is the “rvalue” (right value) We go to the address given by a... and get the contents ( 17 ) b is the “lvalue” (left value) We go to the address given by b...and get the contents? No! We don’t care about 42! We just want the address of b – to store 17 into

42. 42 A note on assignment: Rvalues vs. Lvalues This explains a certain “asymmetry” in assignments involving pointers: char *m = NULL, **pm = NULL; m = “dog”; pm = &m; (char *) (char **) m pm d(char)o(char)g(char)NUL(char) Here, m is an lvalue – It’s understood that the address of m is what’s needed Once again, we need the address of m – but since it’s an rvalue, just plain m will give the contents of m – use & to get the address instead

43. 43 Example: strcpy “string copy” char *strcpy(char *dest, const char *src) (assume that) src points to a sequence of char values that we wish to copy, terminated by NUL (assume that) dest points to an accessible portion of memory large enough to hold the copied chars strcpy copies the char values of src to the memory pointed to by dest strcpy also gives dest as a return value

44. 44 Example: strcpy “string copy” char *strcpy(char *dest, const char *src) { const char *p; char *q; for(p = src, q = dest; *p != '\0'; p++, q++) *q = *p; *q = '\0'; return dest; } d(char)o(char)g(char)NUL(char) (char)(char)(char)(char) (char *) src dest pq d(char)o(char)g(char)NUL(char)

45. 45 Pointer subtraction and relational operations Only meaningful in special context: where you have two pointers referencing different elements of the same array  q – p gives the difference (in number of array elements, not number of bytes between p and q (in this example, 2 )  p < q returns 1 if p has a lower address than q ; else 0 (in this example, it returns 1) (float)(float)(float)(float)(float) (float)(float)(float)(float)(float) (float *) p q

46. 46 Calling Functions by Reference Call by reference with pointer arguments  Pass address of argument using & operator  Allows you to change actual location in memory  Arrays are not passed with & because the array name is already a pointer * operator  Used as alias/nickname for variable inside of function void double( int *number ) { *number = 2 * ( *number ); }  *number used as nickname for the variable passed

47. 1. Function prototype 1.1 Initialize variables 2. Call function 3. Define function Program Output 1/* Fig. 7.7: fig07_07.c 2 Cube a variable using call-by-reference 3 with a pointer argument */ 4 5#include 5#include 6 7void cubeByReference( int * ); /* prototype */ 8 9int main() 10{ 11 int number = 5; 12 13 printf( "The original value of number is %d", number ); 14 cubeByReference( &number ); 15 printf( "\nThe new value of number is %d\n", number ); 16 17 return 0; 18} 19 20void cubeByReference( int *nPtr ) 21{ 22 *nPtr = *nPtr * *nPtr * *nPtr; /* cube number in main */ 23} The original value of number is 5 The new value of number is 125 Notice how the address of number is given - cubeByReference expects a pointer (an address of a variable). Inside cubeByReference, *nPtr is used ( *nPtr is number ). Notice that the function prototype takes a pointer to an integer ( int * ).

48. 48 Using the const Qualifier with Pointers const qualifier  Variable cannot be changed  Use const if function does not need to change a variable  Attempting to change a const variable produces an error const pointers  Point to a constant memory location  Must be initialized when declared  int *const myPtr = &x; Type int *const – constant pointer to an int  const int *myPtr = &x; Regular pointer to a const int  const int *const Ptr = &x; const pointer to a const int x can be changed, but not *Ptr

49. 1. Declare variables 1.1 Declare const pointer to an int 2. Change *ptr (which is x ) 2.1 Attempt to change ptr 3. Output Program Output 1/* Fig. 7.13: fig07_13.c 2 Attempting to modify a constant pointer to 3 non-constant data */ 4 5#include 5#include 6 7int main() 8{8{8{8{ 9 int x, y; 10 11 int * const ptr = &x; /* ptr is a constant pointer to an 12 integer. An integer can be modified 13 through ptr, but ptr always points 14 to the same memory location. */ 15 *ptr = 7; 16 ptr = &y; 17 18 return 0; 19} FIG07_13.c: Error E2024 FIG07_13.c 16: Cannot modify a const object in function main *** 1 errors in Compile *** Changing *ptr is allowed – x is not a constant. Changing ptr is an error – ptr is a constant pointer.

50. 50 The Relationship Between Pointers and Arrays Arrays and pointers closely related  Array name like a constant pointer  Pointers can do array subscripting operations Declare an array b[ 5 ] and a pointer bPtr  To set them equal to one another use: bPtr = b; The array name ( b ) is actually the address of first element of the array b[ 5 ] bPtr = &b[ 0 ] Explicitly assigns bPtr to address of first element of b

51. 51 The Relationship Between Pointers and Arrays  Element b[ 3 ] Can be accessed by *( bPtr + 3 )  Where n is the offset. Called pointer/offset notation Can be accessed by bptr[ 3 ]  Called pointer/subscript notation  bPtr[ 3 ] same as b[ 3 ] Can be accessed by performing pointer arithmetic on the array itself *( b + 3 )

52. 52 Arrays of Pointers Arrays can contain pointers For example: an array of strings char *suit[ 4 ] = { "Hearts", "Diamonds", "Clubs", "Spades" };  Strings are pointers to the first character  char * – each element of suit is a pointer to a char  The strings are not actually stored in the array suit, only pointers to the strings are stored  suit array has a fixed size, but strings can be of any size suit[3] suit[2] suit[1] suit[0]’H’’e’’a’’r’’t’’s’ ’\0’ ’\0’ ’D’’i’’a’’m’’o’’n’’d’’s’ ’C’’l’’u’’b’’s’ ’S’’p’’a’’d’’e’’s’

53. 53 Arrays to functions #include int addNumbers(int fiveNumbers[]); /* declare function */ void main() { int array[5]; int i; cout<<"Enter 5 integers separated by spaces: "; for(i=0 ; i<5 ; i++) { cin>>array[i]; } cout<<”\nTheir sum is: "<<addNumbers(array); Getche(); } int addNumbers(int fiveNumbers[]) { /* define function */ int sum = 0; int i; for(i=0 ; i<5 ; i++) { sum+=fiveNumbers[i]; /* work out the total */ } return sum; /* return the total */ }

54. 54 Case Study: A Card Shuffling and Dealing Simulation Card shuffling program  Use array of pointers to strings  Use double scripted array (suit, face)  The numbers 1-52 go into the array Representing the order in which the cards are dealt deck[ 2 ][ 12 ] represents the King of Clubs Hearts Diamonds Clubs Spades 0 1 2 3 AceTwoThreeFourFiveSixSevenEightNineTenJackQueenKing0123456789101112 Clubs King

55. 55 Case Study: A Card Shuffling and Dealing Simulation Pseudocode - Top level: Shuffle and deal 52 cards Initialize the suit array Initialize the face array Initialize the deck array Shuffle the deck Deal 52 cards For each of the 52 cards Place card number in randomly selected unoccupied slot of deck For each of the 52 cards Find card number in deck array and print face and suit of card Choose slot of deck randomly While chosen slot of deck has been previously chosen Choose slot of deck randomly Place card number in chosen slot of deck For each slot of the deck array If slot contains card number Print the face and suit of the card Second refinement Third refinement First refinement

56. 56 Case Study: A Card Shuffling and Dealing Simulation Pseudocode  Top level: Shuffle and deal 52 cards  First refinement: Initialize the suit array Initialize the face array Initialize the deck array Shuffle the deck Deal 52 cards

57. 57 Case Study: A Card Shuffling and Dealing Simulation Second refinement  Convert shuffle the deck to For each of the 52 cards Place card number in randomly selected unoccupied slot of deck  Convert deal 52 cards to For each of the 52 cards Find card number in deck array and print face and suit of card

58. 58 Case Study: A Card Shuffling and Dealing Simulation Third refinement  Convert shuffle the deck to Choose slot of deck randomly While chosen slot of deck has been previously chosen Choose slot of deck randomly Place card number in chosen slot of deck  Convert deal 52 cards to For each slot of the deck array If slot contains card number Print the face and suit of the card

59. 1. Initialize suit and face arrays 1.1 Initialize deck array 2. Call function shuffle 2.1 Call function deal 3. Define functions 1/* Fig. 7.24: fig07_24.c 2 Card shuffling dealing program */ 3#include 4#include 5#include 6 7void shuffle( int [][ 13 ] ); 8void deal( const int [][ 13 ], const char *[], const char *[] ); 9 10int main() 11{ 12 const char *suit[ 4 ] = 13 { "Hearts", "Diamonds", "Clubs", "Spades" }; 14 const char *face[ 13 ] = 15 { "Ace", "Deuce", "Three", "Four", 16 "Five", "Six", "Seven", "Eight", 17 "Nine", "Ten", "Jack", "Queen", "King" }; 18 int deck[ 4 ][ 13 ] = { 0 }; 19 20 srand( time( 0 ) ); 21 22 shuffle( deck ); 23 deal( deck, face, suit ); 24 25 return 0; 26} 27 28void shuffle( int wDeck[][ 13 ] ) 29{ 30 int row, column, card; 31 32 for ( card = 1; card <= 52; card++ ) {

60. 3. Define functions 33 do { 34 row = rand() % 4; 35 column = rand() % 13; 36 } while( wDeck[ row ][ column ] != 0 ); 37 38 wDeck[ row ][ column ] = card; 39 } 40} 41 42void deal( const int wDeck[][ 13 ], const char *wFace[], 43 const char *wSuit[] ) 44{ 45 int card, row, column; 46 47 for ( card = 1; card <= 52; card++ ) 48 49 for ( row = 0; row <= 3; row++ ) 50 51 for ( column = 0; column <= 12; column++ ) 52 53 if ( wDeck[ row ][ column ] == card ) 54 printf( "%5s of %-8s%c", 55 wFace[ column ], wSuit[ row ], 56 card % 2 == 0 ? '\n' : '\t' ); 57} The numbers 1-52 are randomly placed into the deck array. Searches deck for the card number, then prints the face and suit.

61. Program Output Six of Clubs Seven of Diamonds Ace of Spades Ace of Diamonds Ace of Hearts Queen of Diamonds Queen of Clubs Seven of Hearts Ten of Hearts Deuce of Clubs Ten of Spades Three of Spades Ten of Diamonds Four of Spades Four of Diamonds Ten of Clubs Six of Diamonds Six of Spades Eight of Hearts Three of Diamonds Nine of Hearts Three of Hearts Deuce of Spades Six of Hearts Five of Clubs Eight of Clubs Deuce of Diamonds Eight of Spades Five of Spades King of Clubs King of Diamonds Jack of Spades Deuce of Hearts Queen of Hearts Ace of Clubs King of Spades Three of Clubs King of Hearts Nine of Clubs Nine of Spades Four of Hearts Queen of Spades Eight of Diamonds Nine of Diamonds Jack of Diamonds Seven of Clubs Five of Hearts Five of Diamonds Four of Clubs Jack of Hearts Jack of Clubs Seven of Spades

62. 62 Summary Concept of Pointer Pointer operators  Address and Indirection Pointer Arithmetic Pointer and functions  Pass by Value  Pass by Reference Pointer and Arrays