XV6 - OS

* Lab1_A which contains the xv6 version with process tracing
* Lab1_B which contains the xv6 version with halt system call implemented
* Lab2 which contains the xv6 version with Big data file implemented
* Lab4 which contains the xv6 version with shmget system call 

to run the Lab1_A version-:

* run `make`
* run `make qemu`
it will list the system call name and its return value
NOTE:
	The files i changed:
	* syscall.c

to run the Lab1_B version-:

* run `make`
* run `make qemu`
* run `halt` to run the halt system call
NOTE:
	The files i changed:
	* Makefile
	* Created halt.c
	* sysproc.c
	* syscall.h
	* syscall.c
	* user.h
	* usys.S
	* defs.h

to run the Lab4 version-:

* run `make`
* run `make qemu`
* run `shm_get` to run the shm_get system call
NOTE:
	The files i changed:
	* Makefile
	* defs.h
	* proc.c
	* proc.h
	* syscall.c
	* syscall.h
	* sysproc.h
	* sysproc.c
	* created shm_get.c
	* user.h
	* usys.S
	* vm.c

to run the Lab2 version-:

* run `make`
* run `make qemu`
* run `big *`
NOTE:
	The files i changed:
	* Makefile
	* mkfs.c
	* fs.c
	* fs.h
	* param.h
	* created big.c