OS1

This is a simple operating system developed as a university project. The system is designed to run on RISC-V architecture and implements basic functionalities, including memory management, threading, semaphores, and basic I/O.

System Calls

Memory Management

• void* mem_alloc(size_t size); Allocates memory of size size and returns a pointer to the beginning of the allocated memory.
• int mem_free(void*); Frees previously allocated memory.

Thread Management

• int thread_create(thread_t* handle, void(*start_routine)(void*), void* arg); Creates a new thread that executes the function start_routine with the argument arg.
• void thread_dispatch(); Manually switches context to another thread.
• int thread_exit(); Ends the current thread.
• int getThreadId(); Returns the ID of the current thread.
• void thread_join(thread_t* handle); Waits for the specified thread to finish.
• void thread_joinall(); Waits for all threads to finish.
• int thread_joinalltime(time_t time); Waits for all threads to finish, but no longer than the specified time time.

Semaphores

• int sem_open(sem_t* handle, unsigned init); Initializes a semaphore with the initial value init.
• int sem_close(sem_t handle); Frees resources associated with the semaphore.
• int sem_wait(sem_t id); Decrements the semaphore value and blocks if the value is 0.
• int sem_signal(sem_t id); Increments the semaphore value.
• int sem_timedwait(sem_t id, time_t timeout); Waits for the semaphore with a timeout.
• int sem_trywait(sem_t id); Attempts to decrement the semaphore value without blocking.

Time Management

• int time_sleep(time_t); Pauses thread execution for the specified time.

Input/Output

• char getc(); Reads a single character from standard input.
• void putc(char); Writes a single character to standard output.