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Week Fifteen Agenda. Announcements Revised Final Exam Outline Review week fourteen information Current weeks information Open Source Presenters Angelina LePes Richard Dawber John Ulrich Daniel Miotke Rob Ream Lucas Griffin William Smith. Week Fifteen Agenda.

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Week fifteen agenda
Week Fifteen Agenda

  • Announcements

  • Revised Final Exam Outline

  • Review week fourteen information

  • Current weeks information

  • Open Source Presenters

    Angelina LePes

    Richard Dawber

    John Ulrich

    Daniel Miotke

    Rob Ream

    Lucas Griffin

    William Smith

Week fifteen agenda1
Week Fifteen Agenda

1’s Complement is where all the bits that are a 1 are changed to 0 and all the bits that are 0 are changed to 1. Reversing the digits is also called complementing the number.

Week fifteen agenda2
Week Fifteen Agenda

We will use 4-bit arithmetic to illustrate the point.

Binary Decimal

0111 7

0110 6

0000 0

1111 -0

1001 -6

1000 -7

Week fifteen agenda3
Week Fifteen Agenda

1’s Complement

All negative integers begin with a 1. The most significant bit always tells the sign of the number. The only exception to this rule is the -0.

Week fifteen agenda4
Week Fifteen Agenda

Kill command is use in several operating systems to send signals to running processes. Implementing the kill command, does not always result in terminating a process. The kill command is a wrapper around the kill() system call, which sends signals to processes or process groups on the system that can be referenced by their process ID (pid).

There are many different signals that can be sent to a process, although the ones of most interest are the SIGTERM and SIGKILL.

Week fifteen agenda5
Week Fifteen Agenda

The default signal sent is SIGTERM. Programs that can handle this signal can have useful cleanup operations (save configuration information to a file) before a process terminates.

All signals can be intercepted by a process except the SIGKILL and SIGSTOP. These two signals cause a special function to be executed, that are only seen by the kernel. The SIGKILL kills the process, and SIGSTOP pauses it until a SIGCONT is received.

Week fifteen agenda6
Week Fifteen Agenda

UNIX provides security mechanisms that prevent one user on the system from killing another user’s process. In order for one process to send a signal to another, the owner of the signaling process must be the same as the owner of the receiving process or be the superuser.

Week fifteen agenda7
Week Fifteen Agenda

Other useful signals include the following:

SIGINT signal can be generated with a CTRL+c

SIGTSTP signal can be generated with a CTRL+z

SIGQUIT signal can be generated with a CTRL+\

The SIGQUIT will force the program to do a core dump.

Week fifteen agenda8
Week Fifteen Agenda

Microsoft’s command line interpreter Windows PowerShell, kill is a predefined command alias for the Stop-Process command.

Microsoft Windows XP, Vista and 7, include the command taskkill.

Week fifteen agenda9
Week Fifteen Agenda

The fork () function is used to create a new process from an existing process. The new process is called the child process, and the existing process is called the parent. Their differences can be verified by checking the return value from fork (). The parent gets the child’s pid returned to him, but the child get 0 (zero) to him.

Week fifteen agenda10
Week Fifteen Agenda

The attributes the child inherits from the parent varies depending on the UNIX implementation.


Process credentials (uids and gids)




Open file descriptors

Close on exec flags

Signal handling settings

Week fifteen agenda11
Week Fifteen Agenda

Nice value

Scheduler class

Process group ID

Session class

Current working directory

Root directory

File mode creation mask (umask)

Resource limits

Controlling terminal

Week fifteen agenda12
Week Fifteen Agenda

Unique to child process:

Process ID

Different parent process ID

Own copy of file descriptors and directory streams

Process, text, data and other memory locks are NOT inherited

Process times, in the tms struct

Week fifteen agenda13
Week Fifteen Agenda

Resource utilization are set to zero.

Pending signals initialized to the empty set

Timers created by timer_create operations not inherited

Asynchronous input or output operations not inherited