cstdlib in C++

The C++ cstdlib header (also known as <cstdlib>) provides a collection of functions that deal with basic C library functionalities, including memory allocation, random number generation, and string conversion. Here are some commonly used functions and features provided by the cstdlib header:

1. Memory Management:

• malloc, calloc, realloc: Functions for memory allocation.
• free: Function to deallocate memory allocated by malloc, calloc, or realloc.

1. Random Number Generation:

• rand: Generates a pseudo-random integer between 0 and RAND_MAX.
• srand: Seeds the random number generator with a given value. Note: The random number generation in <cstdlib> is considered basic and not suitable for cryptographic purposes. If you need higher quality randomness, consider using the <random> header.

1. String Conversion:

• atoi, atol, atoll: Functions to convert strings to integers or long integers.
• strtol, strtoul, strtod: Functions for more flexible string-to-numeric conversions.

1. Exit Functions:

• exit: Terminates the program immediately.
• atexit: Registers a function to be called at program termination.

1. Environment Management:

• getenv: Retrieves the value of an environment variable.
• system: Executes a command as if it were a shell command.

1. Other Utilities:

• abs, labs, llabs: Functions to compute the absolute value of an integer or long integer.
• div, ldiv, lldiv: Functions to compute quotient and remainder of integer division.

Here’s a simple example demonstrating the use of some functions from <cstdlib>:

#include <iostream>
#include <cstdlib>

int main() {
    int randomValue = rand();  // Generate a random integer
    std::cout << "Random value: " << randomValue << std::endl;

    char str[] = "12345";
    int intValue = atoi(str);  // Convert string to integer
    std::cout << "Converted value: " << intValue << std::endl;

    return 0;
}

Remember to include the <cstdlib> header at the beginning of your program to use these functions. Keep in mind that many of the functions in this header come from the C standard library, so they might not be the most C++-idiomatic way of performing these tasks. In modern C++ code, you might prefer to use features from the C++ Standard Library or other third-party libraries for more robust and modern functionalities.