PCs ENVIRONMENT and PERIPHERALS Lecture 3

operating system and other system software that control the usage of the computer equipment application programs that carry out a specific task data being processed by application programs data being processed by application programs  Three basic items stored in memory: MEMORY  What is a memory ? Temporary storage place for data, instructions, and information Consists of one or more chips on the motherboard or some other circuit board

How are bytes stored? * Bytes are the basic storage unit in memory * Each byte is stored at a specific location in memory called an address * Each address has a unique identifying number, like the seats on an airplane Each address can hold only a single byte Each address can be full or empty MEMORY seat C22 seat B22 seat A22

MEMORY How is memory measured? Size of memory is measured by the number of bytes available Kilobyte - 1,024 bytes Megabyte - about one million bytes Gigabyte - 1 billion bytes. Terabyte - 1 trillion bytes.

MEMORY What are the two types of memory in the system unit? 1- Volatile Memory  Loses its contents when the computer's power is turned off. 2- nonvolatile memory  Types of memory that retain their contents when power is turned off.

Types of Memory : 1- Random Access Memory (RAM). 2- Read Only Memory(ROM). 3- Flash Memory. 4- Virtual Memory. 5- BIOS. 6- CMOS. MEMORY

1- Random Access Memory(RAM): - Definition: - It is our working memory storage, all the data which PC uses and works with during operating are store here. Why it is important? Because it is the memory that your computer system uses to store the data of all open programs and applications. providing enough data from the hard disk for microprocessor to use at any given time without making it wait.

1- Random Access Memory(RAM): What is random access memory (RAM)?  Memory chips that can be read from and written to by the processor and other devices  When the computer starts, operating system files are loaded from a hard disk into RAM  As additional programs and data are requested, they also load from storage into RAM  Most RAM is volatile

1- Random Access Memory(RAM): RAM memory has two types: 1-Dynamic Random Access Memory (DRAM) 2-Static Random Access Memory (SRAM)

RAM Chips 10

2- Read Only Memory (ROM): Definition: Read Only Memory (ROM) is computer memory that can permanently store data and applications within it. ROM Types: 1- PROM (Programmable Read Only Memory ): The data can be erase and rewrite on ROM. 2- EPROM (Erasable Programmable Read Only Memory) : you can erase data and write on it more than one time. 3- EEPROM (Electrically Erasable Programmable Read Only Memory ): you can write without erase all data without special tool.

2- Read Only Memory (ROM): What is read-only memory (ROM)? - Memory chips that contain data, instructions, or information that is recorded permanently - Data can only be read, cannot be modified - Nonvolatile — Contents not lost when the computer is turned off

3- Flash Memory: What is Flash Memory? Is a type of EEPROM Nonvolatile memory that can be erased electronically and reprogrammed. Stores data and programs on many handheld computers and devices such as Camera and mobile phone.

4- Virtual Memory: - Because the processor speed so high compare with RAM and hard disk, and computer try to have a good speed for transfer data: - There is a way to fetch unused space on HD and determine small spaces that not used, and use it as virtual memory. - So, we have a new way to help RAM.

4- Virtual Memory(continue): Practical: From your computer determine virtual memory size. To check the virtual memory: - My computer –(Right click on a white space)  properties  advanced system sitting  Advanced options tab  inside performance section click setting  from advanced options tab  virtual memory. (to change size use change).

Virtual Memory(practical):

5- BIOS: What is it? Basic Input Output System(BIOS): Sequence of instructions the computer follows to load the operating system and other files when you first turn on the computer. Stored on ROM. They are necessary to start the computer  load the operating system  and other files when you first turn on the computer

5- BIOS  The first software the computer runs is the one that inside these encoded computer chips  When you turn on the computer, Power On Self Test or (POST) ensure that all the basic input and output devices are working probably. (how ?)  When power is turned on, POST (Power-On Self-Test) is the diagnostic testing sequence that a computer's basic input/output system (or "starting program") runs to determine if the computer keyboard, random access memory, disk drives, and other hardware are working correctly.

5- BIOS  If the necessary hardware is detected and found to be operating properly, the computer begins to boot. If the hardware is not detected or is found not to be operating properly, the BIOS issues an error message which may be text on the display screen and/or a series of coded beeps, depending on the nature of the problem.  This program builds by the company.

5- BIOS

6- CMOS: information - A separate memory chip, called Complementary Metal-Oxide Semiconductor (CMOS): chip stores the information that describes specific device parameters. data - CMOS does not store programs, only data that is read by BIOS to be able to talk to the changeable hardware.

6- CMOS: -Stored as RAM. -CMOS also acts as a clock to keep date and time updated while the PC is off. - CMOS chip is volatile (kept alive by battery). This way the information contained in the CMOS are always present even if the computer power is turned off.