Computer Science

Computer Science

1. Topic 3

   • Hardware
     • CPU
       • Control Unit
         • Decodes instructions received from main memory and coordinates the actions of the other parts of the other parts of the CPU in order to execute them
       • ALU
         • The arithmetic logic unit that performs arithmetic and logic operations on data
       • Registers
         • A bank of registers that provide fast, temporary storage for instructions, intermediate results and data.
           • some registers are general purpose. others have designated function.
       • Buses
         • Address Bus
           • Carries the address of the memory location that the CPU will read from or write to.
             • It is unidirectional. only the CPU can put an address on it
         • Data Bus
           • Holds the value being read from or written to memory
             • It is biderectional
         • Control Bus
           • It carries command signals from the control unit to other components so that they know whether to read or write data, and status signals to the cpu
             • It is bidirectional
       • Clock
         • The clock sends out electronic signals at regular intervals to all the other hardware components in order to synchronize their actions.
       • Fetch-decode-execute cycle
         • Decode
           • The control unit decodes the instructions
         • Execute
           • The control unit sends signals to the other components of the CPU instructing them what to do
         • Fetch
           • The control unit places the memory address of the next instruction on the address bus. It sends a read signal to RAM along the control bus
     • Secondary Storage
       • Magnetic Storage
         • Magnetic storage uses the fact that magnets have north and south poles and that these can be used to represent binary 1s and 0s.
           • This type of storage is used in hard drives and magnetic tape drives
       • Optical storage
         • Optical storage is familiar to you as CDs and DVDs. It uses differences in light reflected off the storage off the surface of a disk to represent bits.
       • Solid-state storage
         • Also known as Flash memory
         • Represents bits by little pools of trapped electrons on a microchip
     • Embedded systems
       • They have a limited functionality and customised hardware and software
       • Microcontroller
         • Made up of a CPU, memory, input/output ports and circuitry
   • Software
   • Programming Languages
     • Bad Programming Practices
       • Not properly designs
       • Typos in Your Code
       • Failing to Use Good Encryption to Protect Data

2. Maths

   • The smallest unit of data is the bit.
     • They can store a single 0 or a 1
   • Time = File size (In Bits) / Network speed (In bps)
   • File size = sample rate × bit depth × time

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