Why does my program give “NULL used in arithmetic”

Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.

Want to improve this question? Update the question so it’s on-topic for Stack Overflow.

Closed 7 years ago.

I wrote the following;

string words;
int a=0;
getline(cin,words);

while(words[a]!=NULL)
{                           
     a++;                    
}        
cout<<a<<endl;

It worked correctly, but when I added the line at the end:

string words;
int a=0;
getline(cin,words);

while(words[a]!=NULL)
{
      a++;                       
}
cout<<a<<endl;

if(words[1]=="a") {cout<<"the letter is a";}

It no longer works. Why?

Related Posts:

  1. Why the switch statement cannot be applied on strings?
  2. How to convert string to char array in C++?
  3. How can I convert a std::string to int?
  4. Easiest way to convert int to string in C++
  5. std::string to char*
  6. How to convert string to char array in C++?
  7. C++ — expected primary-expression before ‘ ‘
  8. C++ string to double conversion
  9. Conversion from string to char – c++
  10. What is `CString`?
  11. How do I include the string header?
  12. Differences between C++ string == and compare()?
  13. How to convert a char array to a string?
  14. Split a string using C++11
  15. How do I iterate over the words of a string?
  16. How to convert an instance of std::string to lower case
  17. Check if a string contains a string in C++
  18. How do I iterate over the words of a string?
  19. Returning an empty string : efficient way in c++
  20. Replace part of a string with another string
  21. C++ string to double conversion
  22. What is use of c_str function In c++
  23. How to reverse an std::string? [duplicate]
  24. std::string to char*
  25. How to convert a std::string to const char* or char*
  26. How do I tokenize a string in C++?
  27. Why use string::iterator rather than index?
  28. Why am I getting string does not name a type Error?
  29. C++ deprecated conversion from string constant to ‘char*’
  30. identifier “string” undefined?
  31. Press Enter to Continue
  32. Converting a vector to string
  33. Parsing a comma-delimited std::string
  34. How can I convert const char* to string and then back to char*?
  35. std::string formatting like sprintf
  36. Sorting Characters Of A C++ String
  37. basic_string::_M_construct null not valid after constructing subvector of strings
  38. How to copy a string of std::string type in C++?
  39. How to return a string from a C++ function?
  40. std::out_of_range error?
  41. What is the difference between isdigit() and isnumber()?
  42. Convert char* to string C++
  43. printf with std::string?
  44. Convert a String In C++ To Upper Case
  45. Right way to split an std::string into a vector
  46. Read whole ASCII file into C++ std::string
  47. C++: std does not have member “string”
  48. Right way to split an std::string into a vector
  49. string subscript out of range error
  50. C++ String Variable Declaration
  51. Returning an empty string : efficient way in c++
  52. Split a string into an array in C++
  53. splitting a string into an array in C++ without using vector
  54. Remove spaces from std::string in C++
  55. Remove spaces from std::string in C++
  56. c++ convert string to hex
  57. How can I iterate through a string and also know the index (current position)?
  58. c++ parse int from string [duplicate]
  59. Hash function for a string
  60. C++ strings and pointers
  61. How to Convert a C++ String to Uppercase
  62. std::wstring VS std::string
  63. C++ Simple hangman game
  64. std::cin input with spaces?
  65. Remove First and Last Character C++
  66. C++ Remove punctuation from String
  67. C++ Convert string (or char*) to wstring (or wchar_t*)
  68. C++ – Assigning null to a std::string
  69. How to alphabetically sort strings?
  70. Hash function for a string
  71. Reading string by char till end of line C/C++
  72. How do I check if a C++ std::string starts with a certain string, and convert a substring to an int?
  73. Dynamically allocated string array, then change it’s value?
  74. Fastest way to Convert String to Binary?
  75. Why I cannot cout a string?
  76. How to print a string in C++
  77. std::string length() and size() member functions
  78. How to convert QString to int?
  79. Which is faster C++ String length() or size()?
  80. How do I create a random alpha-numeric string in C++?
  81. Trying to use int in getline
  82. error: switch quantity not an integer
  83. Reading a string from file c++
  84. How to change string into QString?
  85. Remove last character from C++ string
  86. Function stoi not declared
  87. Converting String to Cstring in C++
  88. c++ sizeof( string )
  89. How to do std::string indexof in C++ that returns index of matching string?
  90. variable or field declared void
  91. Function stoi not declared
  92. Understanding error “terminate called after throwing an instance of ‘std::length_error’ what(): basic_string::_S_create Aborted (core dumped)”
  93. convert string to size_t
  94. ‘setprecision’ is not a member of ‘std’
  95. enum to string in modern C++11 / C++14 / C++17 and future C++20
  96. Converting bool to text in C++
  97. Why are there two different getline() functions (if indeed there are)?
  98. How to find and replace string?
  99. Declaration is incompatible with type
  100. I’m getting the error “stoi is not a member of std” in myprogramminglab [duplicate]

Leave a Comment