Difference between char* and char** (in C)

char* is a pointer to char, char ** is a pointer to a pointer to char.

char *ptr; does NOT allocate memory for characters, it allocates memory for a pointer to char.

char arr[10]; allocates 10 characters and arr holds the address of the first character. (though arr is NOT a pointer (not char *) but of type char[10])

For demonstration: char *str = "1234556"; is like:

char *str;         // allocate a space for char pointer on the stack
str = "1234556";   // assign the address of the string literal "1234556" to str

As @Oli Charlesworth commented, if you use a pointer to a constant string, such as in the above example, you should declare the pointer as const – const char *str = "1234556"; so if you try to modify it, which is not allowed, you will get a compile-time error and not a run-time access violation error, such as segmentation fault. If you’re not familiar with that, please look here.

Also see the explanation in the FAQ of newsgroup comp.lang.c.

Related Posts:

  1. How do I properly compare strings in C?
  2. How to remove .html from URL?
  3. How to convert an int to string in C?
  4. What does strcmp() exactly return in C?
  5. C – The %x format specifier
  6. Reversing a string in C
  7. Passing string to a function in C – with or without pointers?
  8. Trim a string in C [duplicate]
  9. How to remove first character from C-string?
  10. Standard function to replace character or substring in a char array?
  11. The difference between char * and char[] [duplicate]
  12. Pointer to a string in C?
  13. How does strtok() split the string into tokens in C?
  14. What is lexicographical order?
  15. How to convert an int to string in C?
  16. Regex not operator
  17. Arrow operator (->) usage in C
  18. working of \n in python [duplicate]
  19. Regex not operator
  20. What is a string of hexadecimal digits?
  21. Extract a substring using PowerShell
  22. How to convert an int to string in C?
  23. Extract substring in Bash
  24. Regex not operator
  25. Pointer Arithmetic
  26. What does “dereferencing” a pointer mean?
  27. How to convert a string to integer in C?
  28. What does “dereferencing” a pointer mean?
  29. char *array and char array[]
  30. How do I create an array of strings in C?
  31. What is the difference between \r\n, \r, and \n? [duplicate]
  32. string to string array conversion in java
  33. What is the difference between \r\n, \r, and \n? [duplicate]
  34. C pointers and arrays: [Warning] assignment makes pointer from integer without a cast
  35. Regex how to match an optional character
  36. What is the difference between char s[] and char *s?
  37. How to remove punctuation in python?
  38. “error: assignment to expression with array type error” when I assign a struct field (C)
  39. What is use of c_str function In c++
  40. What is the difference between const int*, const int * const, and int const *?
  41. How do I properly compare strings in C?
  42. What is the difference between a “line feed” and a “carriage return”?
  43. What is the difference between const int*, const int * const, and int const *?
  44. Python: TypeError: cannot concatenate ‘str’ and ‘int’ objects
  45. Ignoring upper case and lower case in Java
  46. How to convert an int to string in C?
  47. How to replace all double quotes to single quotes using jquery?
  48. Convert character to ASCII numeric value in java
  49. Passing by reference in C
  50. Returning string from C function
  51. Generate random string/characters in JavaScript
  52. Why does the arrow (->) operator in C exist?
  53. “[ ]” vs. “[[ ]]” in Bash shell
  54. How do I create an array of strings in C?
  55. How to trim whitespace from a Bash variable?
  56. Return char[]/string from a function [duplicate]
  57. How to check if a string is a number?
  58. How to get the filename without the extension from a path in Python?
  59. sprintf like functionality in Python
  60. Difference between char* and const char*?
  61. What does ** do in C language?
  62. Lua string.format options
  63. How to convert integer to string in C?
  64. #31 expression must have integral type
  65. n-grams in python, four, five, six grams?
  66. How do you pass a function as a parameter in C?
  67. Invalid pointer error on invoking free() after malloc in C
  68. Alphabet range in Python
  69. How do I lowercase a string in C?
  70. How do I create an array of strings in C?
  71. expression must have integral type
  72. How do you pass a function as a parameter in C?
  73. How to make an array with a dynamic size? General usage of dynamic arrays (maybe pointers too)?
  74. expression must have integral type
  75. How do you pass a function as a parameter in C?
  76. C free(): invalid pointer
  77. How to trim whitespace from a Bash variable?
  78. What’s wrong with my code? What is argv[1]?
  79. Return char[]/string from a function
  80. Valgrind: Invalid read of size 1
  81. How to clear all the elements of array in C?
  82. Constant pointer vs Pointer to constant
  83. What is the difference between ‘ and ” in JavaScript?
  84. How do I concatenate const/literal strings in C?
  85. How to remove the character at a given index from a string in C?
  86. Center text in fixed-width field with stream manipulators in C++
  87. Split string with delimiters in C
  88. Warning: return from incompatible pointer type in C
  89. Is the sizeof(some pointer) always equal to four?
  90. C# – Illegal characters in path
  91. \n or \n in php echo not print [duplicate]
  92. Warning: assignment from incompatible pointer type
  93. Mips how to store user input string
  94. How to create an array of strings in C?
  95. strcmp giving segmentation fault
  96. C++ strings and pointers
  97. PadLeft function in T-SQL
  98. Why am I getting this error: “data definition has no type or storage class”?
  99. bash : Bad Substitution
  100. Initialization from incompatible pointer type warning when assigning to a pointer

Leave a Comment