Major Hardware Components of a Computer System • Central Processing Unit • Auxiliary Storage • Input Devices • Output Devices Central Processing Unit • Arithmetic/Logic Unit (ALU): processes data arithmetically (addition, subtraction, multiplication, division) or logically (greater than, less than, equal to) • Control Unit: works with the operating system to move data between auxiliary storage and main memory; and between main memory and the ALU • Main Memory: contains both program instructions and the data that is required. • A single machine can have multiple CPUs to share processing tasks (co-processors, multiprocessing), but each CPU can execute only a single task. Inside the System Unit • Main component: motherboard – Circuit board that “houses” integrated circuits (microscopic elements … wires, transistors, etc…) required to make the digital pulse flow inside of the computer. Pulses flow from component to component via the “bus” – Some microcomputers contain a special local bus (VESA or PCI) which increase data transfer rates to the display and/or storage devices Motherboard (cont.) – Attachments to the motherboard include: • Main Memory: types of main memory include: – RAM - temporary (includes virtual memory storage). Include RAM cache – ROM - permanent – CMOS - semipermanent battery powered » Memory chips attach with either a DIP (dual inline pin - old PCs) or as a SIMM (single inline memory module) board – When add main memory, make sure add-on chips are compatible • Real time clock (current date and time) • Microprocessor or CPU (central processing unit) – Control Unit: traffic cop portion of the CPU – ALU: arithmetic logic unit processes all math and logical operations performed by the computer Motherboard (cont.) • Expansion slots/add on boards - allow “cards” that attach various peripheral devices to the motherboard – monitors, hard drive, internal fax/modem, network cards,etc – PCMCIA slots: special slots developed for laptops to attach devices and add on RAM • Expansion devices may provide an external “port” which you connect a cable to. Device ports will either be from an internal or external bay in the system unit. – Serial Port: transmits data one bit at a time (modem) – Parallel Port: transmits 8 bits simultaneously (printers, backup devices, etc.) – SCSI Port: allows several devices to be chained together and connected through a single SCSI (small computer system interface) – MIDI Port: musical instrument digital interface Main Memory • Random Access Memory (RAM): allows data and instructions to be accessed randomly from any memory location (address). Primary storage. – Volatile - lost when power is turned off • Read Only Memory (ROM): usually contains programs that help the computer system operate: – can only be read: cannot be written to or altered by the user (usually) – ROM is not volatile Main Memory • Data and instructions are stored as BITS (binary digits). Everything from our world is translated into a computer recognizable format called binary (zeros or ones) – The combination of binary digits represents our letters or numbers. One character represented is equal to a byte. • Memory capacity is measured in bytes. Today’s most common measurement is megabytes Kilo = 1,000 (KB) Thousand Mega = 1,000,000 (MB) Million Giga = 1,000,000,000 (GB) Billion • Bytes are composed using either the ASCII coding system (7 bits = character) or EBCDIC (8 bits = character) Microprocessor Families • Intel (IBM) and Motorola (Macintosh 68000) two main manufacturers • Microprocessors are “families” - upward increases in speed (early SX vs DX chips) • Increase in bus capacity indicates a new generation The Boot Process • When you turn your computer on, the following activities happen: – Power is sent to the internal fan and the motherboard – The boot program stored inside of ROM activates – The Power-On Self-Test (POST)runs and tests required system components – The operating system/environment is loaded – Configuration and customization routines are executed which set your computer environment Input/Output Peripheral Devices • Badge Reader • SASD & DASD drives • Bar-code Reader • Printers • Cartridge & cassette – Page vs line or character drives printers – Impact vs nonimpact • CD Rom • Plotter • Digital camera • Robotics • Digital tables & scanners • Speech synthesizer • Keyboard, mouse, pens • VDT • MICR • Microforms • Voice • OCR • Touch screen Storage Required because main memory is limited, expensive and volatile. • Sequential Access Storage Devices (SASD): data is stored in sequential order. Retrieval is also sequential. – Storage media is magnetic tape. – Supports batch processing environment – Excellent form of backup • Direct Access Storage Devices (DASD): data can be stored and retrieved randomly. – Storage capacity is referred to as density. How tightly packed data is on the disk. – DASD is required for transaction processing. • Memory capacity is measured in bytes. Today’s most common measurement is kilobytes, megabytes and gigabits. Printer Considerations • Dot matrix - low price & inexpensive to operate. Lower quality. Impact - can print carbon forms. Color option. Slow. • Ink jet - moderate price & better output. Color option. Nonimpact. Quieter. • Laserjet - more expensive. Faster. High quality. Nonimpact. Display Considerations • Screen size- diagonal measurement from corner to corner. Popular sizes are 14”, 15” and 17” • Dot pitch - measure of image clarity. The smaller the dot pitch, the crisper the image or resolution. • Video adapters/cards impact image resolution and display speed. Today, most monitors are Super VGA (1024 x 768)and use non-interlaced projection technology (flicker) • Laptop - liquid crystal display (LCD). Passive matrix vs active matrix screen (display method which impacts image quality). Active matrix is much better but more expensive and can have problems. DASD • Floppy Disk: removable DASD. Most common density is 1.44Mb. • Hard Disk: usually don’t remove (but newer devices you can). Higher storage capacity than floppy disks. Faster access. – Winchester drive architecture is not removable. – Can be drives that have removable disk platters. – Optical disk: CD_ROM (read-only) Erasable optical disk is also available. WORM - write once, read many. – Flash memory: main memory on a card. Non volatile. PCMCIA card. DASD cont. • All data stored on DASD media is stored in pie- shaped sectors that determines how much data is moved into and out of main memory at a time. • Virtual storage: operating system uses hard disk drive as an extension of main memory. • Cache memory: operating system assumes that most data used by an application is accessed over and over again. Cache is a special area in main memory where such data is put instead of paging it back and forth to DASD. DASD cont • WORM: write-once, read many. (CD ROM). Also have rewriteable CD ROM. • Floptical Disk: optical storage capacities on floppy disk. • DVD: Digital video disk • Hierarchical Storage: use of many different types of DASD & SASD devices to achieve storage requirements. Other considerations: • Desktop vs Laptop - expansion slots and capability – Port replicators vs docking station – Pointing device. Track ball, touch pad, erase point. – Power management & battery considerations (hot swap) • Multimedia devices - sound cards, speakers and MPC standards • Bundled software Common File Types • Data Files: files of information created when people use various types of software • Executable Files: Types of systems files that are used by the computer to perform certain tasks. With some executable files (.exe., .com, .bat) you can initiate the processing while with others the computer initiates the process (.dll, .sys, .drv, etc.) • You and your AUTOEXEC.BAT file. Anatomy of a Filename • Rules for creating valid filenames (appropriate characters, length of names, etc.) depends on the operating system being used. • Components of a filename consist of: File name from you Drive Designation C:/foldername/filename.ext Folder/subdirectory File extension name supplied by the program File Storage • Logical Storage: • Physical Storage How you perceive that data How data actually is stored on an auxiliary resides on your storage media auxiliary storage media File/disk directory File Allocation Table No indication of (FAT) fragmentation Fragmentation is normal Measurements of Computer Power • Clock speed: electronic pulses used to synchronize processing. Faster clock speeds result in more operations in a give amount of time. Measured in megahertz (MHz). • Bus width: determines how much data can be transferred at any one time. 16 bit, 32 bit, 64 bit. – IBM’s Microchannel (MCA) Architecture vs EISA (open architecture) • Word size: number of bits/bytes manipulated at once. Same as the bus width. • Other determinants include main memory capacity, MIPs. • This is not the same as throughput but it can affect throughput..
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