Monday, January 14, 2008

Guide to Digital Media Interaction and Design Part 10

Multimedia
- Audio
- Video
- Animation
- Printed or Spoken Words
- Music and Other Audio
- Still images

Audio
- Dialog in audio is also available as text
o Some people prefer text
o Needed by the deaf
- To set Mood, keep volume low
- To get attention, keep it brief
- Give option to turn sound off

Video
- A powerful medium to convey motion, facial expression and audio
- Very slow for users with dialup connections

Tips for Recording Video
- Use A Tripod
o Better image
o Improves compression due to reduction of motion
- Use A neutral background
o Better visually
o Improves compression due to reduction of motion
- Get in close to your subject

Vector-based vs. Pixel-based Animation
Pixel-based formats stores color information for each pixel in an image. Vector-based format list sets of points that define shapes that appear in the animation.

Advantage of Vector-based animation is that the file is very compact due to the use of vector based geometries and resolution is independent resulted the ability to view it at any resolution and the image remains sharp.
Disadvantage is that user much download specific player to view the files.

Posted by Zack at 6:53 PM

Sunday, January 13, 2008

Guide to Digital Media Interaction and Design Part 9

HBS
- Hue: Where a color lies around another color
- Brightness: Light or dark or in between
- Saturation: Purity of a color

Harmony Schemes
- Monochromatic: colors of same or similar hue, differing in brightness and/or saturation.
- Complementary: color approximately opposite each other on a color wheel.
- Analogous: color adjacent to each other from any segment of a color wheel.
- Triadic: three colors appropriately equally space around a color wheel.

Posted by Zack at 1:07 PM

Guide to Operation System Part 9

Address Binding
Address Binding is the assignation of physical address to lines of instructions of a program when that program is loaded into primary memory.

Three Types of Address Binding
- Compile Time Binding
- Load Time Binding
- Run Time Binding

Memory Allocation
- Fixed Partition (Internal Fragmentation may occur here)
o First Fit
o Best Fit
o Worst Fit
- Variable Partition (External Fragmentation may occur here)
o Memory is allocated to processes on a need to and available basis

Compaction
Compaction is the solution to solve external fragmentation. The goal is to shuffle the memory contents to place all free memory together in one big block.

Posted by Zack at 12:42 PM

Saturday, January 12, 2008

Guide to DMID Part 7 Optimized

I have updated the Guide for DMID part 7. You can find it in November entry.

Posted by Zack at 7:01 PM

Guide to Operation System Part 8

Deadlock
A deadlock is a situation where a group of two or more process/threads each holds at least one resource while making a request on another and all request cannot be satisfied because the requested resource is held by another process that is being blocked or waiting for another resource.

Four Conditions for Deadlock to occur:
- Mutual Exclusive: Once a process has been allocated a particular resource, the threads in the process have exclusive use of the resource. No other processes can use a resource while it is allocated to a process.

- Hold and Wait: A process hold a resource at the same time it requests another one.

- Circular Wait: A situation can rise in which process P1 holds resource R1 while one of its threads requests resource R2, and process P2 while one of its threads requests resource R1.

- No Preemption: Resources can be release only by the explicit action authority.

Four Approaches of managing Deadlock
- Prevention
- Avoidance
- Detection & Recovery
- Manual Intervention

Banker’s Algorithm (Deadlock Avoidance)
When a new process enters the system, it must declare the maximum number of resources it needs. The system will determine whether allocations of these resources will leave system in a safe state. If yes, resources are allocated. If no, the process will wait until some other process release enough resources.

Posted by Zack at 5:40 PM

Guide to Operation System Part 7

Critical Section

A critical section is a section of code in a program which cannot be executed by more than one thread at the same time.

Possible Solutions to Critical Section

-Disabling Interrupts

-Using a Lock Variable

-Transactions

-Semaphores

Semaphores

A semaphore is OS ADT (Abstract Data Type) that is capable of controlling the use of a limited resource in a multiprogramming environment. The 2 operations are:

-P(x): This blocks the process/thread if the resource is not available.

-V(x): This increment of counter, indication that a process/thread has finished with the critical resource.

Difference between Asynchronous IPC and Synchronous IPC

For Asynchronous IPC, the sending or the receiving operation will not cause the process/thread to block.

While in Synchronous IPC, the operation will cause the process/thread to block in the following situations:

-If the receiving party is not listening, in the case of the sending operation.

-If the sending party is not sending yet, in case the case of the receiving operation.

Posted by Zack at 3:25 PM

Thursday, January 10, 2008

Guide to Operation System Part 6

Scheduling
- Scheduling is the task of managing CPU sharing among a pool of ready processes or threads and it is only possible if context switching facility exist.

- A Scheduler chooses a ready thread to allocate to the CPU when available.

- A Schedule Policy determines when it is time for a thread to be removed from the CPU and allocate it to another thread.

- The Scheduling Mechanism determines how process manager can determine it is time to interrupt the CPU and how thread can be allocated to and removed from CPU.

Scheduling Mechanism
Consist of 3 Logical Parts:
- Enqueuer: help to lineup process (in ready list)
- Dispatcher: try to bring the process to CPU so that the process can start executing
- Context Switcher: save state of old process and switch to a new process

Invoking the Scheduler (A mechanism to call the scheduler)
- Voluntary Call: Process blocks itself and calls the scheduler
- Involuntary Call: External force(interrupt) blocks the process and calls the scheduler

Sharing of CPU
- Voluntary CPU Sharing: also known as non-preemptive (not forced) scheduling
o Process voluntarily release the CPU to be reallocated to other process, usually happens after the process s ends or process executes a system call to release CPU (e.g. yield machine instruction).

- Involuntary CPU Sharing: also known as preemptive (forced) scheduling
o Uses interrupt system to periodically force an interruption of any process’s execution. Interrupt is generated by an internal timer, which the timer is usually programmable by software so that the Interval (Time Slice) can be adjusted by the OS.

Scheduling Performance
If a process continually gets ignored by the scheduler, even though it is ready, this phenomenon is called Starvation.

Non-preemptive Scheduler
- First-Come-First-Served (FCFS): Scheduler picks up first job to arrive in the ready list.
- Shortest Job First (SJF): Scheduler picks up shortest job to arrive in the ready list.
- Priority (PR): Scheduler picks up the job with highest priority in the ready list.

Preemptive Scheduler
- Shortest Job First (SJF): Scheduler picks up shortest job to arrive in the ready list.
- Priority (PR): Scheduler picks up the job with highest priority in the ready list.
- Round Robin (RR): Scheduler gives a short Interval (Time Slice) to each job.
- Multi-Level Queues: Implement multiple queues with different scheduling policies.

Posted by Zack at 10:29 PM

Guide for DMID Part 6 Optimized

Today i have optimized the Guide for DMID part 6. It can be found in November entry.

Posted by Zack at 9:29 PM

Wednesday, January 09, 2008

Mini Guides For DMID and OS

I will be doing some guides for DMID and OS these few days. Older guides can be found in my archive dated back at around October 2007.

CHEERS~: