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  1. // If you are not sure what some lines of code do, try looking back at
  2. // previous example programs, notes, or ask a question.
  3.  
  4. #include <iostream>
  5.  
  6. using namespace std;
  7.  
  8. // This is totally unrestricted - we can edit the pointed-to data and reassign 'value,'
  9. // which will actually change where the passed-in pointer is pointing to at the call site.
  10. void func1(char*& value);
  11.  
  12. // Here, we can still edit the pointed-to data and reassign 'value,' but this cannot
  13. // effect its caller.
  14. void func2(char* value);
  15.  
  16. // Here, we can reassign value within func3, but we cannot edit the pointed-to data.
  17. void func3(const char* value);
  18.  
  19. // Here, we can edit the pointed-to data, but we cannot reassign 'value' within func4.
  20. void func4(char* const value);
  21.  
  22. // Finally, we can neither reassign 'value' nor edit its data.
  23. void func5(const char* const value);
  24.  
  25.  
  26. int main() {
  27.  
  28. 	char cstring[50];
  29. 	int integer = 0;
  30.  
  31. 	// Creates an integer pointer and assigns it to the address of "integer"
  32. 	int* valuePtr = &integer;
  33.  
  34. 	cout << valuePtr << endl; // This outputs the address of "integer"
  35. 	cout << *valuePtr << endl; // This will output the actual value of "integer"
  36. 	*valuePtr = 5; // This actually sets the value in "integer" to 5
  37. 	cout << integer << endl; // This will output the 5
  38.  
  39.  
  40. 	// Creates a pointer to a character and points it to the first element in the c-string array
  41. 	char* stringPtr = cstring;
  42. 	cout << "Enter a string: ";
  43. 	cin >> cstring;
  44.  
  45. 	// Iterate through the string using the pointer
  46. 	while(*stringPtr) {
  47. 		cout << *stringPtr << endl;
  48. 		stringPtr++;
  49. 	}
  50. 	// Now, "stringPtr" will be pointing off the end of the array, so using it would likely result in a seg fault.
  51. 	// It's a good idea to set it to NULL so that you program can check if it is valid in the future.
  52. 	stringPtr = NULL;
  53.  
  54.  
  55. 	// Declares a void pointer and sets it to point to "integer"
  56. 	void* voidPtr = &integer;
  57. 	*(int*)voidPtr = 10; // Sets the value to 10 - note that you must specify that "voidPtr" is pointing to an integer
  58. 	cout << endl << *(int*)voidPtr << endl; // Again, you must specify that "voidPtr" is pointing to an integer
  59.  
  60.  
  61. 	// End program
  62. 	cout << endl;
  63. 	system("pause");	
  64. 	return 0;
  65. }
  66.  
  67.  
  68. // See Prototypes
  69.  
  70. void func1(char*& value) {
  71. 	value = "a";
  72. 	// It may not make sense why we might want to change the pointer in main 
  73. 	// right now, but it will when we talk about dynamic memory next week.
  74. }
  75.  
  76. void func2(char* value) {
  77.  
  78. 	// Sets the values in the c-string pointed to by value
  79. 	for(int i = 0; *value; i++) {
  80. 		*value = 'a' + i;
  81. 		value++;
  82. 	}
  83. 	value = NULL;
  84. }
  85.  
  86. void func3(const char* value) {
  87.  
  88. 	// Can't edit the pointed-to values
  89.  
  90. 	value = NULL;
  91. }
  92.  
  93. void func4(char* const value) {
  94.  
  95. 	// Sets the values in the c-string pointed to by value
  96. 	for(int i = 0; *value; i++) {
  97. 		value[i] = 'a' + i;
  98. 	}
  99.  
  100. 	// value = NULL; can't do this
  101. }
  102.  
  103. void func5(const char* const value) {
  104.  
  105. 	// Can't edit anything
  106. }
  107.  
Success #stdin #stdout #stderr 0s 15240KB
comments (?)
stdin
copy 
hello!
stdout
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0x7ffd7cc29c0c
0
5
Enter a string: h
e
l
l
o
!

10
stderr
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sh: 1: pause: not found
https://ideone.com/egtY1e
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
secret

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