Notes on Cherno's C++ Tutorial: Strings

Requires prior knowledge of pointers and arrays because you'll find that strings and arrays are closely related.

First, what is a string? Essentially, a string is a sequence of characters. Characters refer to letters, numbers, symbols, and essentially anything that represents text. For us, it’s necessary to represent the shape and format of text on a computer in some way.

A single character, an entire paragraph, a word, a bunch of words... all of these are referred to as strings, or a string of text.

In C++, there is a numeric type called char, which is short for character. It occupies 1 byte of memory. It’s useful because it allows you to convert pointers to char pointers, enabling pointer arithmetic based on bytes. It’s also useful for allocating memory buffers. If you want to allocate 1KB of memory, you can simply allocate 1024 chars.

It’s also useful for strings and text because the default way C++ handles characters is through ASCII characters. Characters can also be larger than one byte (e.g., Chinese, Japanese), and can be 2-4 bytes in size.

If we only use 1 byte to represent a character, 1 byte = 8 bits, which means we have \(2^8=256\) possibilities. Clearly, this isn’t enough to accommodate all languages. Therefore, we have UTF-16, which is a 16-bit character encoding, giving us \(2^{16}=65536\) possibilities.

However, in the base C++ language without any libraries, using only primitive data types, char is 1 byte.

1. const* char

Rule of thumb: If you don’t use the new keyword, don’t use delete.

const char* name = "Cherno";  // C-style string definition
name[2] = 'a';  // Won't work. If you know you won’t modify the string, use const; otherwise, remove it.

Starting from C++11, assigning string literals directly to non-const char* pointers is considered unsafe behavior. Therefore, use:

char name[] = "Cherno";

The 00 character in the image is called the null termination character. This lets us know where the string ends and makes it easier to determine the size of the string ^26e746.

char name2[6] = { 'C','h','e','r','n','o' };
std::cout << name2 << std::endl;   // Cherno烫烫烫烫烫......

An array guard was allocated, but there’s no null termination character, so cout doesn’t know where to stop printing.

char name2[7] = { 'C','h','e','r','n','o','\0'}; // You can also write it as 0 directly.

Normal output.

2. std::string

std::string has a constructor that accepts a char pointer or a const char pointer. It also has many built-in methods.

std::string name = "Cherno";
std::cout << name << std::endl;          // Cherno
std::cout << name.size() << std::endl;   // 6

String Concatenation

std::string name = "Cherno" + "hello";  // '+': cannot add two pointers

As mentioned earlier, these are const char arrays, not actual strings.

std::string name = "Cherno";
name += "hello";   // Chernohello

Or:

std::string name = std::string("Cherno") + "hello!";

3. Passing Strings to Other Functions

void PrintString(const std::string& string) // Pass by reference, not by copy, and ensure it’s not modified.