Processing & Storage. Computer Storage. Primary Storage/Main Memory/RAM - Volatile - changing. Used for data and programs needed for processing by CPU soon. Secondary Storage - Non-volatile - permanent. Used for data and programs to be processed later. Data Representation.
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Computer Storage • Primary Storage/Main Memory/RAM - Volatile - changing. Used for data and programs needed for processing by CPU soon. • Secondary Storage - Non-volatile - permanent. Used for data and programs to be processed later.
Data Representation • Data - raw, unprocessed info. (letters, numbers, special symbols) • Binary Code - what the computer reads. ASCII and EBCDIC - standards for determining data representation • Binary - only 2 possible selections (0/1, on/off, magnetized/not magnetized)
Bit - Binary Digit - single binary 0 or 1 • Byte - group of adjacent bits that represent 1 letter, 1 number, or 1 special symbol. Often, 8 bits =1 byte. • Parity/Check Bit - Extra bit appended to the end of a byte to signify computer error in data.
Storage Capacity • 8 bits = 1 byte = 1 character • 1000 bytes = 1 kilobyte (K) • 1000K = 1 megabyte (MB) • 1 billion bytes = 1 gigabyte (GB) • 1 trillion bytes = 1 terabyte (TB)
File Organization/Storage Devices • Sequential - data stored/ retrieved in sequential order. Slow. Inexpensive. Historical data/backup. Magnetic tape can ONLY use sequential storage.
Direct/Relative/Random - data stored/retrieved directly, in any order, as needed. Requires Direct Access Storage Device. (DASD) • Index-Sequential - stored sequentially, with index (DASD)
Examples of DASD’s • Diskette/Floppy Disk- portable, slow, inexpensive, small storage capacity compared to other DASD’s. 5-1/4”, 3-1/2”. 360K - 1.44MB (700 pages of 2000 chars. ) ED - 2.8MB • Hard Disk - permanently installed disk(s). 2 - 9+ GB (1 GB: 500,000 pages of 2000 chars.)
Large Computer System Disk Storage • Removeable Packs • Fixed Disk Drives - 1 path • RAID (redundant array of inexpensive disks) - multiple paths simultaneously (faster)
Hard Disk Cartridge- inserted into disk drive. Portable. 100 MB - 1.2 GB • Flash Memory- lightweight, small fast storage on credit-card sized units. portable 100 MB+ • NEW S99- Sony Memory Stick - gum-stick-sized storage 4-8MB
Optical Disks- laser burns spots (bits) onto disks. Disks read by reflecting light from these bits. Slower access than hard disks. • CDs - Compact Disks - MOST are read-only (CD-ROM) 650 MB Also CD-R and CD-E/CD-RW • DVDs - Digital Video Disks - optical disks with revised format 4.7 - 17 GB
Microcomputer Architecture • Enhanced Integrated Drive Electronics - EIDE - inexpensive connection for devices - slower than SCSI (16MB per second) • Small Computer System Interface - SCSI - devices daisy-chained. Faster than EIDE (40MB per second)
2 Types of Processing • Batch - Data collected and processed later, in a group • On-line/Real-time - data processed at time of transaction
System Unit Where processing is done. • Motherboard - Circuit board - contains most of the electronic components of the system. • Central Processing Unit (CPU) - “brains” On PC, contained on microprocessor chip
Parts of CPU • Control Unit - Directs and coordinates computer activities. Tells other parts of the computer system what to do. Uses machine language (binary code) unique to each type of computer. • Arithmetic/Logic Unit (ALU) Performs all arithmetic functions.
Registers - Temporary storage units in CPU. Used for data/instructions being used now • Wordsize - size (in bits) of registers • More/larger registers lead to faster processing • Bus - electronic communications path for data/instructions. • Wider bus - more data - leads to faster processing
Coprocessors • Processors used in addition to the main CPU • Math • Graphics
Machine Cycle • Steps the CPU carries out to perform 1 instruction. • Synchronized by internal clock • clock speed expressed in megahertz (MHz) - 1 million cycles per second. • faster speed leads to faster processing
Machine Cycle Steps • Instruction Cycle • Fetch • Decode • Execution Cycle • Execute • Store
Memory • Random Access Memory (RAM)/ Main Memory/ Primary Storage - stores programs/data needed shortly by CPU. Non-permanent, volatile • Read-Only Memory (ROM) - Memory that can be read from - not added to or changed. Comes with computer. Permanent, non-volatile.
Cache Memory - High speed memory to hold frequently used instructions - CPU looks here first. volatile. • Flash Memory - Memory on cards - can be used as extra RAM but is non-volatile. • Video Memory - VRAM - Stores display images for monitor.
Ports • Sockets on outside of system unit used to connect peripheral devices. • Parallel - multiple bits transferred simultaneously over short distance • Serial (COM ) - 1 bit after the other • Video Adapter - for monitor • SCSI - daisy-chained devices • Game - joysticks • Infrared - wireless/radiowaves
ExpansionSlots/Boards • Slots - sockets on the motherboard • Cards/Boards - circuit boards that plug into slots (ex: sound card) Used for memory, coprocessing, controlling devices