Multi-threaded Cooperative Operating System Emulator

This is a cooperative single core OS made in java for my ICSI 412 class.

How it works:

This OS Emulator creates a seperate thread for each individual UserLand Process, and a thread for the Kernel. Each UserLand Process runs int it's own thread and pauses it's own thread and passes the necessary information to a designated spot in the OS. Then the kernel thread runs and performs the requested action.

Supported Kernel Calls:

Process Management:

• OS.createProcess(): Create a new process. Optionaly with a specified priority.
• OS.switchProcess(): Switch between processes.
• OS.sleep(): Puts the calling process to sleep for a specified amount of time.

Device I/O:

• OS.open(): Opens a device, given a device and a specifier, and returns a file ID.
• OS.read(): Reads from the specified device.
• OS.write(): Writes to a specified device.
• OS.seek(): Moves the filePointer within the device.
• OS.close(); Safely closes the speficied device.

Interprocess Communication:

• OS.getPID(): Gets the PID of the current process.
• OS.searchPID(): Finds a process with a specified name.
• OS.sendMessage(): Sends a message to the process with the specified PID.
• OS.waitMessage(): Retrieves the first message on it's message queue, or waits until it receives a new message.

Virtal Memory Management:

• OS.allocateMemory(): Allocates simulated physical pages on the hard drive with continuous virtual page numbers.
• OS.freeMemory(); Frees allocated memory for use by other processes.