Major Hardware Components of a Computer System Central

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 (MB) Million Giga = 1, 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 Bar-code Reader Cartridge & cassette drives CD Rom Digital camera Digital tables & scanners Keyboard, mouse, pens MICR Voice OCR Touch screen • SASD & DASD drives • Printers – Page vs line or character printers – Impact vs nonimpact • • • Plotter Robotics Speech synthesizer VDT Microforms

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. 44 Mb. • 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 pieshaped 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 name File extension supplied by the program

File Storage • Logical Storage: How you perceive that data is stored on an auxiliary storage media • Physical Storage How data actually resides on your auxiliary storage media File/disk directory No indication of fragmentation File Allocation Table (FAT) 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. .