Chapter 3: Where are programs and data Stored?

How important is this chapter to understanding how a computer works? 7 (on a scale of 1-10 with 10 being most important.

How important is this chapter to understanding how to use a computer? 5 or 6

Memory and Storage Usage Von Neumann Architecture – when a program is running it must be contained in memory at that time. Storage is the place where “stuff” is kept when it is not being used.

Types of Memory RAM – random access memory Used for running programs and manipulating data ROM – read only memory Contains startup commands and specialized software firmware

Types of Memory (continued) CMOS Contains configuration information Registers Inside the CPU where the data is actually manipulated Cache Used to speed up processing Buffers

Types of Storage Disk Magnetic Hard disk (fixed disk) Floppy disk Removable disk Optical CD rom DVD rom CD-R/CD-RW/DVD-R/DVD-RW …

Types of Storage (continued) Tape Open reel Cassette Used mostly for backup Integrated Circuits Flash Memory

Memory and Storage Characteristics Memory is volatile Transitory is the term used by the book. Storage is permanent (where permanent means a long time but not forever)

Physical Characteristics of Magnetic Disks Platters Individual disks Tracks Concentric circles Sectors Pie shaped wedges Blocks Intersection of a track and a sector

Physical Characteristics of Magnetic Disks (continued) Clusters The smallest number of blocks that can be accessed at one time Cylinders “Vertical” collections of tracks. Difference between optical and magnetic

Logical Organization of Disks Bootable disks and boot records Disk directory Subdirectories File allocation schemes Data area

Virtual Memory Using Storage as memory disk only Increases capacity but decreases speed Paging Thrashing

Data travel during processing discuss

How much memory is enough? It depends What Operating System? What do you do? How much data do you manipulate?

No really, how much memory do you need? My experience Based on current O/S (Windows XP) Based on current prices of memory (Sept 2005) One 256mb chip = 25 dollars Based on current applications… 512mb or 1024 mb

Deleting a file vs. Erasing a file Note I have never heard these terms used in this manner. Nonetheless… How to remove Mark directory Mark data area Overwrite data area

Fragmentation Occurs after lots of use of a disk Defragmentation will generally speed up disk access because the head will not have to move as much during reading and writing Do it occasionally (monthly) Time consuming

Protecting Your Computer Viruses Intrusion Privacy

Viruses You should have an up to date virus detection and removal program on your computer. The U’s standard is McAfee VirusScan version 8

Intrusion Your computer should have a reliable firewall system. There’s one built into windows which protects your system from incoming but does not protect it from outgoing. I use Zone Alarm Pro which protects from both. There are lots of other good programs Learn how to recognize Firewall problems

Privacy Spyware Added to your system when you surf or install “free” programs Spybot Search and Destroy is my choice Adaware is also popular.