C++: سلاسل C

"Hello" in memory:
+---+---+---+---+---+----+
| H | e | l | l | o | \0 |
+---+---+---+---+---+----+
 0 1 2 3 4 5 ← indices

char stringName[Size];

#include <iostream>

int main() {
 char name[20]; // Can store 19 chars + 1 \0
 
 name[0] = 'H';
 name[1] = 'e';
 name[2] = 'l';
 name[3] = 'l';
 name[4] = 'o';
 name[5] = '\0'; // Don't forget the null terminator!
 
 std::cout << "Name: " << name << std::endl; // Hello
 
 return 0;
}

Name: Hello

#include <iostream>

int main() {
 char name = "Hello"; // ✅ Compiler auto-adds \0, array size is 6
 
 std::cout << "Name: " << name << std::endl;
 
 return 0;
}

#include <iostream>
#include <cstring> // Must include this header

int main() {
 char name = "Hello";
 
 std::cout << "String: " << name << std::endl;
 std::cout << "Length: " << std::strlen(name) << std::endl; // 5（excluding \0）
 
 return 0;
}

char name = "Hello";
std::cout << sizeof(name) << std::endl; // 6（Array size）
std::cout << std::strlen(name) << std::endl; // 5（effective character count）

#include <iostream>
#include <cstring>

int main() {
 char src = "Hello";
 char dest[20];
 
 std::strcpy(dest, src); // Copy src to dest
 
 std::cout << "src：" << src << std::endl;
 std::cout << "dest：" << dest << std::endl;
 
 return 0;
}

std::strncpy(dest, src, sizeof(dest) - 1); // Copy at most sizeof(dest)-1 characters
dest[sizeof(dest) - 1] = '\0'; // Manually add null terminator

#include <iostream>
#include <cstring>

int main() {
 char greeting[50] = "Hello, ";
 char name = "World";
 
 std::strcat(greeting, name); // Append name to greeting
 
 std::cout << greeting << std::endl; // Hello, World
 
 return 0;
}

#include <iostream>
#include <cstring>

int main() {
 char str1 = "Hello";
 char str2 = "Hello";
 char str3 = "World";
 
 std::cout << "strcmp(str1, str2) = " << std::strcmp(str1, str2) << std::endl;
 std::cout << "strcmp(str1, str3) = " << std::strcmp(str1, str3) << std::endl;
 
 return 0;
}

char str1 = "Hello";
char str2 = "Hello";

if (str1 == str2) { // ❌ Error: Comparing addresses, not content
 // ...
}

if (std::strcmp(str1, str2) == 0) { // ✅ Correct：Use strcmp to compare content
 // ...
}

#include <iostream>

int main() {
 char name[20];
 
 std::cout << "Please enter your name: ";
 std::cin >> name; // ✅ Can read strings (but no spaces)
 
 std::cout << "Hello，" << name << "！" << std::endl;
 
 return 0;
}

#include <iostream>

int main() {
 char name[50];
 
 std::cout << "Please enter your full name: ";
 std::cin.getline(name, 50); // ✅ Read entire line (including spaces)
 
 std::cout << "Hello，" << name << "！" << std::endl;
 
 return 0;
}

#include <iostream>
#include <cstring>

int main() {
 char str[100];
 std::cout << "Please enter a string: ";
 std::cin.getline(str, 100);
 
 int vowels = 0;
 for (int i = 0; i < std::strlen(str); i++) {
 char c = str[i];
 if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' ||
 c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U') {
 vowels++;
 }
 }
 
 std::cout << "Vowel count: " << vowels << std::endl;
 
 return 0;
}

Please enter a string: 
Vowel count: 

Please enter a string: Hello World
Vowel count: 3

#include <iostream>

int main() {
 char name[5] = "Hello"; // ❌ Error: "Hello" Need 6 chars (including \0), but array size is only 5
 std::cout << name << std::endl;
 return 0;
}

char name[6] = "Hello"; // ✅ Correct：Array size must be at least 6

#include <iostream>

int main() {
 char str1[20];
 char str2 = "Hello";
 
 str1 = str2; // ❌ Error: Cannot assign to array
 str1 = "World"; // ❌ Error: Cannot assign to array
 
 return 0;
}

#include <iostream>
#include <cstring>

int main() {
 char str1[20];
 char str2 = "Hello";
 
 std::strcpy(str1, str2); // ✅ Correct：Use strcpy to copy
 std::cout << str1 << std::endl;
 
 return 0;
}

#include <iostream>
#include <cstring>

int main() {
    char src[] = "Hello";
    char dest[20];

    std::cout << "src length: " << strlen(src) << std::endl;

    strcpy(dest, src);
    std::cout << "After copy: " << dest << std::endl;

    return 0;
}

src length: 5
After copy: Hello