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Computer Files & Data Storage

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Computer Files & Data Storage STORAGE, FILE CONCEPTS, FILE ORGANIZATION, UTILITIES (Pages 16-19, 194-199, OFF25-OFF37 - Discovering Computers & Microsoft Office 2016) I. Computer files – all data and software instructions are stored as “files”. Everything recorded on a secondary storage device is a file, the only exception is a folder, but a folder is a storage container, not a file. More on folders later. A. Program or software files (software instructions) are created by a computer programmer and generally cannot be modified by a user (unless considered open-source). When you install software files, they go to a specific location (Program Files folder if using Windows). It’s important that you not move, rename, or delete program files because your computer is dependent on them to perform actions while processing. When software is installed it’s placed in a specific location, when needed, the CPU goes to that location. Program files provide instructions for all tasks completed by the computer. 1. You can identify a program file by its unique extension: “.EXE”, “.COM”, “.BAT”, “.DLL”, “.SYS”, or “.INI” - there are others. Given the sensitivity of software files, most users elect to hide them. B. Data files – a user creates a data file while saving within an application program. Unlike software files that are already named when you install them, Users are responsible for assigning the names to data files. 1. File naming conventions is the term that identifies the guidelines for assigning data file names. The guidelines vary according to your operating system (see table on next page). File names in Windows 10 may consist of up to 255 characters, you're not allowed to use reserved characters or certain reserved words (see table). File extensions are provided by the application program used while creating the file and serve to identify the format of the data in the application. Office 2016 file Fall 2016 1 extensions are as follows: WORD - .docx, Excel - .xlsx, PowerPoint - .pptx, Access - .accdb. II. Selecting secondary storage media A. Modern computers employ 3 different storage technologies: Magnetic, Optical, & Solid State. There are advantages & disadvantages between each. When selecting a secondary storage technology and associated media, the following factors should be taken into consideration: 1. Capacity - the capacity of all storage media is expressed in “bytes”. Remember that every character you save will occupy a byte of storage. For instance, the character X will be stored on a byte represented as 0101 1000 (all a computer understands is binary code) Fall 2016 2 2. Hard drives provide the greatest storage capacity of any PC media (TB capacity). Flash drives & DVD disks provide the greatest capacity of portable or mobile media (GB capacity). Least capacity? Floppy diskettes (legacy – KB & MB capacity). Common byte units include: a. Kilobyte (KB) - one thousand bytes (floppies - PC) b. Megabyte (MB) - one million bytes (floppies, CD - PC) c. Gigabyte (GB) - one billion bytes (USB flash, DVD, hard drive - PC) d. Terabyte (TB) - one trillion bytes (hard drives - PC) e. Petabyte (PB) – one quadrillion bytes (mainframes, super) f. Exabyte (EB) - one quintillion bytes (mainframes, super) 3. Access time – The time it takes the CPU to access recorded files from storage is measured in fractions of a second, again, fractions of a second! Think about that. Access time units are as follows: a. millisecond – 1/1000 of a second b. microsecond – 1 millionth of a second c. nanosecond – 1 billionth of a second d. picosecond – 1 trillionth of a second e. Solid State devices provide the quickest access, Magnetic Tape the slowest f. These time units are faster than the blink of an eye 4. Cost – Prices for storage devices differ, like most any commodity; primarily higher costs are based on devices with greater capacity. Magnetic floppies are the least expensive (less than a dollar – again, low capacity) Hard drives are the most expensive simply because they have the greatest capacity. But, if we consider price on a byte for byte basis, Solid State media is more expensive. Example: A 2 TB Solid State drive would be more expensive than a 2 TB Magnetic Hard drive. Byte for byte storage on Solid State is more expensive. Because the greatest capacity drives today are magnetic, we generally still consider Magnetic Hard Drives to be the most expensive storage drives. I don’t believe we have 2TB Solid State drives. 5. Durability – How long will saved data remain on disc? Optical and Solid State storage devices are considered more durable when compared to magnetic storage (see related sections further on in the notes). Fall 2016 3 Data is considered more secure on non-magnetic devices; magnetic devices only guarantee storage for 3 years, not very long. This will be explained further in the next outline. Bottom line, data storage is not permanent or forever, it has a limited life. 6. Versatility – Can I use different media on a particular storage drive? Will a CD drive read a floppy diskette? No. Can I insert my flash drive into a DVD drive? No. The only device that can support multiple media is a DVD drive. A DVD drive can read all or any form of optical discs (CD, DVD), this is the only device capable of supporting different media discs. All other devices can only use specific media. Fall 2016 4 .
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