-----------------------------------------70 Points Project -----------------------------------

Team Members:
=============
Garima Gehlot (SBU ID: 110167347)
Arpit Singh (SBU ID: 110162005)
Sagar Mehra (SBU ID: 110166108)

------------------------------------------ Features -------------------------------------------

1. Warm up:: Kernel printf, Timer, Keyboard, IDT, handlers
2. Physical Memory, Virtual Memory, Mapping
3. 4-Level Paging, CR3 setup
4. Ring 0 to Ring 3 switch, Context Switch, COW fork
5. Tarfs and Elf Loading
6. Auto grow stack and Dynamic heap allocation
7. SEGV handling
8. Shell with "PATH","PS1","cd","|" and "&"
9. Script handling with #!. 

----------------------------------------- Memory Mapping ------------------------------------

			PHYSICAL	VIRTUAL
			========	========

physbase		0x200000	0xffffffff80200000

VMAP_START		0x0		0xfffffffff0000000
VMAP_END		0x7ffe000	0xfffffffff7ffe000

VIDEO_BUFFER	        0xb8000		0xFFFFFFFF800B8000	

USER_STACK_TOP				0xf000000
STACK_LIMIT				8192

HEAP					0x0800000
HEAPEND					0x1000000

Features Supported on Shell:
============================
1.  cd                : change the current working directory
2.  clear/cls         : to clear the screen
3.  echo $PATH        : to display the path
4.  echo $PS1         : to display the PS1
5.  echo <var>        : prints the input given
6.  export PATH=      : update the path variable
7.  export PS1=       : update the PS1 variable
8.  ls                : list the contents in current directory
9.  ps                : list all runnning process
10. sleep             : sleep for input time in seconds
11. kill -9           : kills the process whose pid is provided as input
12. help              : prints the features supported in shell
13. pwd               : prints current working directory
14. exit              : exits the given process
15. cat               : prints the content of file
16. sh                : runs the script provided as input having shebang(!#)
17. ulimit            : prints the upper limits
18. ./<bin>           : binary execution of binary with name <bin>
19. /rootfs/bin/<bin> : executes binary located at /rootfs/bin/<>
20. shutdown          : shutdown the OS
21. pipe (" | ")      : single level pipe support
22. Background(" & ") : Supports execution of background process and scripts
23. alarm             : Runs alarm after provided time 

Syscall supported:
=================
1. open
2. read
3. write
4. lseek
5. close
6. dup
7. dup2
8. opendir
9. readdir
10.closedir
11.sleep
12.getcwd
13.waitpid
14.execve
15.getpid
16.getppid
17.fork
18.brk
19.exit
20.chdir
21.listprocess
23.clearscreen
24.shutdown
25.alarm

--------------------------------- References ---------------------------------

1. BrokenThorn
2. Osdevwiki and Forum
3. AMD64 Architecture Programmer's Manual Volume 2: System Programming
4. Bran(OSDEVER)
5. JamesM's kernel development tutorials 

Reference OS (x64):
1. HelenOS-0.5.0
2. Shovelos