Index a pointer as if it were an array : array pointer « Array « C++ Tutorial

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2. Array
3. array pointer

#include <iostream> 
#include <cctype> 
using namespace std; 
 
int main() 
{ 
  char *p; 
  int i; 
  char str[80] = "This Is A Test"; 
 
  cout << "Original string: " << str << "\n"; 
 
  p = str;
 
  for(i = 0; p[i]; i++) { 
    if(isupper(p[i])) 
      p[i] = tolower(p[i]); 
    else if(islower(p[i])) 
      p[i] = toupper(p[i]); 
  } 
 
  cout << "Inverted-case string: " << str; 
 
  return 0; 
}

Original string: This Is A Test
Inverted-case string: tHIS iS a tEST