Multimedia Glossary: P
A B C D
E F G H I
J K L M
N O P Q R
S T U V W X Y Z
- PAL
- Phase Alternation Line
- an analogue video standard used in Western Europe and Great Britain, Africa,
Australia, China, South America. The frame rate is 25 frames per second
(fps). PAL scans the cathode ray tube (CRT) horizontally 625 times to form
the video image.
- Other standards are NTSC and SECAM
- PEP
- Protocol Extension Protocol
- an extension mechanism for HTTP
- Phase Alternation Line
- See PAL
- PICS
- Platform Independent Content Selection
- PICS is an infrastructure for associating labels (metadata) with Internet
content. These labels are used for code signing, privacy, and intellectual
property rights management.
- PICS was originally designed to assist in the control of
internet content -- to prevent children and sensitive users from
stumbling upon unwanted sites.
- Ping
- A utility that sends a packet to an Internet server and wait for a response.
It is used to check if a host (i.e. a server) is running.
Top
- Pixel
- Picture Element
- A Picture Element (pixel) is a single addressable location on a computer
screen, i.e. the smallest unit of display that can be controlled by software.
- Size:The actual size of a pixel is relative, depending
on the quality of the screen, or how the screen is configured. A web author
can therefore never be sure of the exact size or quality in which documents
would be rendered.
- Color: Color can be assigned to a pixel, but the software
color palette is translated into hardware according to manufacturer specifications,
so the color of a pixel is also not absolute. sRGB
is one attempt to standardize on the delivery of color.
Top
- Platform Independent Content Selection
- See PICS
- PNG
- Portable Network Graphics
- W3C recommendation on 1 October 1996.
- PNG is a bitmap compression method for image
files. This format is recommended by the W3C to be used instead of GIF.
PNG supports 16.7 million colors, it is lossless and also supports index
color, grayscale, true color, and is streamable. It is thus the best compression
method (better than GIF or JPEG) for use on the web.
Top
- Point-to-Point Protocol
- See PPP
- Port
- Communication with servers take place through ports, which usually have
unique numerical addresses. These numbers may be changed by a system-administrator,
but generally they do not need to be specified or tampered with. Here is a
list of typical web-related ports.
-
Port numbers
-
| Service |
Port |
| FTP |
21 |
| Gopher |
70 |
| HTTP |
80 |
| HTTPS |
442 |
| NNTP |
118 |
| NNTPS |
563 |
| Telnet |
23 |
Top
- Portable Network Graphics
- See PNG
- Portable Operating System Environment
- See POSIX
- Portal
- See Home Page
- POSIX
- Portable Operating System Environment
- A body making decisions on Unix standards.
Top
- Protocol Extension Protocol
- See PEP
- PPP
- Point-to-Point Protocol
- A driver used for accessing a network communications protocol
over a phone line. PPP allows connection to the TCP/IP protocol
which is the basic internet protocol. A dial-up user gets connected
to The Internet via PPP.
Top
- Protocol
- A protocol is a standard of technical conventions allowing communication
between different electronic devices. It consists of a set of rules for the
communication between devices. From a human perspective, different customs
of greeting would constitute human greeting protocols. Some cultures raise
their right hands; some shake hands, some kiss on the cheeks, some breathe
the same air, and so on.
Top
A B C D
E F G H I
J K L M
N O P Q R
S T U V W X Y Z
© 2003, 2004 Jacques Steyn