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cs170 - Coggle Diagram

- - - - 3 steps in execution
        
        step 1 retrieves data and instructions from main memory
        
        step 2 executes instructions
        based on processing
        directives that are “hard
        coded” into its silicone.
        
        step 3 puts (writes) results to
        main memory.
        
        if stored in a file,
        it must be loaded from disk to main memory
      - fetches data/instructions from
      - “brains” of the PC
      - CPU memory
        
        16-64 CPU registers
        
        dozens of mem cells
      - instruction set
        
        wired into the cpu's circuitry
        
        instruction execution order
        
        not wired into the CPU, determined by a program written in machine language
    - - one part of memory in von Neumann architecture
      - holds 4 things
        
        output data
        
        persistent storage, display, buffers. etc.
        
        pixel
        
        a picture element, which is a single dot on the display, each with its own brightness and color setting, which are configured to from an image on a panel/paper
        
        number of bits required for a display
        
        memory =
        
        numberOfPixels ∗ numberOfComponents ∗
        
        (log numberOfShades/ log 2)
        
        generally expressed in bytes
        
        input data
        
        keyboard, mouse, pens, etc.)
        
        memory-mapped I/O
        
        locations in main memory reserved for input connections and output connections
        
        ex: how the OS manages memory when pressing a key on a keyboard
        
        since keyboards are mapped to main memory, they send info about the key pressed to the input connection in main memory, then the keyboard sends a signal to the CPU telling it a key was pressed. The CPU then fetches the info from the input connection initially sent by the keyboard to main memory. This transfer occurs through the system bus.
        
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        I/O modules
        
        special purpose processors
        
        ex:
        
        used to compute color values for individual pixels on a display, instead of the CPU doing it, the CPU sends a signal to the output connections of main memory, which then go to the I/O modules
        
        data
        
        instructions.
      - volatile
      - aka RAM
        
        Random access memory
        
        random access
        
        types of memory
        
        sequential access
        
        to get information at the other end of the disk, you must traverse all the data between the beginning and the end
        
        sequential access memory
        
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        to get information from any location in ram does not require you to traverse the information held between each location
      - biillions of mem cells
    - - reads/writes directly main memory using DMAC
      - DMA
        
        direct memory access
        
        managed by
        
        DMAC
        
        specialled processing units in persistent memory
        
        allows input/output directly to/from memory
        
        direct memory access controller
        
        definition
        
        allows input/output directly to/from memory
      - any means of storing data after PC is powered off
        
        can mean
        
        ROM
        
        definition
        
        Read-only memory
        
        hard disk drive
        
        peripheral memory
        
        random access, persistent
        
        solid disk drive
        
        100x faster than HDD, 1000x slower than main memory, fully electronic, no mechanical parts
        
        disk
        
        a single disk can be used with different operating systems and have incompatble file systems (ex: unix and windows)
        
        disk memory
        
        nonvolatile
        
        trillions of memory cells
        
        aka
        
        nonvolatile
      - no direct communication
        between PM & CPU
        
        because
        
        disk is 100x-1000x slower than CPU
  - - - allows transfer of data to/from cpu, Main memory, persistent memory
  - - - Application Software
        
        software dealing with user data
        
        makes the computer system accessible to the end user at Level App7
      - System Software
        
        software dealing with access to limited computer resources
        
        makes the computer accessible to the applications designers
        
        ex:
        
        operating system
        
        responsible for 3 things:
        
        File management
        
        Memory management
        
        OS ensures CPU has access to the correct parts of memory when needed. Even when that memory is not in RAM.
        
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        Processor management
        
        manages the CPU's limited resources(registers, cores, i/o paths) to meet user needs and stay productive
        
        common OSs
        
        Unix-based: Mac OS/X, Linux, iOS
        
        Linux-based: Android
        
        Other: Windows
    - - takes inputs, process them, and produce outputs
    - - input and processing are known,
        output is unknown
    - - input and output are known,
        processing is unknown
      - 4 General problem-solving guidelines
        
        › Understand the problem, break into subproblems.
        
        › Outline a solution.
        
        › Solve each part of your outlined problem.
        
        › Test your solution on the computer.
  - - - handled by
    - - program
        
        algorithm written for execution on a computer, cant be written in English, only in one of the seven languages
        
        7 levels of abstractions for a computer system
        
        7 Application Level
        6 High-order language level
        5 Assembly level
        4 operating system level
        3 instruction set architecture level
        2 microcode level
        1 logic gate level
        
        and their corresponding languages
        
        Level 7 (App7): Language dependent on applications program
        
        Level 6 (HOL6): Machine-independent programming language
        
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        Level 5 (Asmb5): Assembly language
        
        Level 4 (OS4): Operating system calls
        
        Level 3 (ISA3): Machine language
        
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        Level 2 (Mc2): Microinstructions and register transfer
        
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        Level 1 (LG1): Boolean algebra and truth tables
        
        program execution time
        
        time = instructions (cycles/instruction) (time/cycle)
        
        # of instructions x number of clock cycles to complete an instruction x amount of time in one clock cycle
        
        execution time of a task within a program
        
        The system performance equation
        
        timeToCompleteProgram = numberOfISA3instructions x averageNumberOfMc2instructionsToCompleteOneISA3Instruction x timeToCompleteOneCycle(T=1f, the GHz rating)
        
        where T = period, number of seconds per cycle
        
        f = frequency rating of the CPU
        
        result measured in time per program
        
        ex
        
        1 Suppose your CPU is rated at 2.5 GHz and you execute a program task on your app that requires the execution of 16 million ISA3 instructions. If each ISA3 instruction executes an average of 3.7 Mc2 instructions, what is the execution time of the program task?
        
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      - data
      - document
  - - - SQL
        
        Structured Query Language
        
        sequel
      - Non-SQL
        
        every other type of database
  - - - as electrical signals, which are voltage levels inside the electronic circuits, where each signal is either at high voltage level == 1 or low voltage level == 0
        
        bit
        
        smallest unit of digital information
        
        each bit in a computer system occupies space in the circuit comprised of the electronic components that maintain its value
        
        sequence of bits
        
        cell
        
        arBITrary collection of sequnetial bits, not the same throughout the computer system
        
        larger # of bits == wider range of numeric/character values
        
        The number of values stored by a sequence of n bits
        
        2^n
        
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        common cell sizes
        
        Nibble - collection of 4 bits
        
        Byte - collection of 8 bits
        
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        Word - collection greater than a byte (16, 32, 64,etc.)
        
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        unsigned binary addition
        
        1+0 =
        1+1 =
        1+1+1 =
        
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        symbol: b
        
        binary digit, as it can only be one of two digits: 0 or 1
  - - - time it takes the CPU to execute one of the instructions in its instruction set
        
        measured in
        
        GHz
        
        unit of frequency
        
        hertz
        
        1 cycle / 1 second
        
        billion cycles / 1 second
    - - time it takes to move information from one component of the system to another
        
        bandwidth equation
        
        time to move information from one component of the system to another
        
        bandwidth of the channel x transmission time
        
        results measured in bits per second or bytes per second
        
        MB/s != mb/s
        
        ex
        
        A typist is entering some text on a computer keyboard at the rate of 35 words per
        
        minute. How large must the bandwidth of the channel be to accommodate the information flow
        
        between the typist and the computer system? Assume that each word is followed by one space
        
        character, on average.
        
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        A typist is entering some text on a computer keyboard at the rate of 35 words per
        
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        minute. How large must the bandwidth of the channel be to accommodate the information flow
        
        between the typist and the computer system? Assume that each word is followed by one space
        
        character, on average.
        
        Including one space character after each word, the typist enters 36 characters per minute.
        
        bandwidth
        
        quantity of information that the channel can carry per unit of time
        
        channel
        
        connection between the source and the destination over which information flows
        
        ex:
        
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        high bandwidth == more information transferred per unit of time
        
        low bandwidth == less info transferred per unit of time