Referencing row indices
Each character in a string has a number (called 
index), and indexing in the C# programming language starts from zero. That is, the first character has index 0, the second - 1, and so on.
String characters can be accessed by indexes, which are indicated in square brackets 
s[i].
 
Example 
| String S | 
H | 
e | 
l | 
l | 
o | 
| Index | 
S[0] | 
S[1] | 
S[2] | 
S[3] | 
S[4] | 
Important!
When accessing a string element at index 
i, the type 
s[i] is not 
string but 
char. This means that this is not a string, but a character that corresponds to some integer in the character code table. In particular, when you add two elements of type 
char , you get an integer - the addition of the codes of these elements. However, if you display 
s[i], the 
i-th character of the string will be displayed, not the number corresponding to it.