Unit 3 Hardware and Software Pt. 2

− The structure of language statements in a computer program is called the SYNTAX − A programming language that uses natural language statements is called a HIGH LEVEL LANGUAGE − When programs are written in this type of language they need a TRANSLATOR to convert them into MACHINE CODE − A programming language that is written using mnemonic codes is called ASSEMBLY LANGUAGE language. − This is an example of a LOW LEVEL LANGUAGE

− Memory that is directly accessed by the CPU − An example is RAM / ROM − RAM stores programs and data that are currently in use and ROM stores boot-up instructions − RAM is volatile and ROM is non volatile − RAM typically has more storage than ROM − Volatile memory means data is lost if device is powered off, non-volatile is when data remains even after device is powered off.

− Storage that is not directly accessed by the CPU − An example is HDD / SSD − Stores data / files that can be accessed at a later stage − Non volatile

SSD better than HDD: − Faster read/write operation − Less latency − Produces less heat // needs less cooling − Less susceptible to interference/magnets − Less power consumption HDD better than SSD −Cheaper − Infinite amount of read/write cycles

SSD − Flash storage − Uses transistors and controls gates − Can be NAND/NOR technology − Stores data by flashing it onto the silicon chips − Controlling using the flow of electrons through transistors/chips/gates − The electric current reaches the control gate and flows through to the floating gate to be stored − When data is stored the transistor is converted from 1 to 0 / 0 to 1 − Some use EEPROM technology

− It has platters − Platters/disk divided into tracks − Platter/disk is spun − Has a read/write arm that moves across storage media − Read/writes data using electromagnets − Uses magnetic fields to control magnetic dots of data − Magnetic field determines binary value Benefits: − Has more longevity than solid state storage − Has more read/write cycles than solid state storage − Cheaper per unit of data − Trusted technology used for many year

How its read − Red laser is used, laser beam shone onto disk − Disc is rotated on a constant speed to be read − Surface is covered in track − Data is represented on the surface using pits and lands − Pits represent binary valves − Pits reflect light back differently How data is written − Laser beam is used − Laser makes indentations on the surface of the disc − Data is written in spiral track − Pits and lands represent binary values − It is non-volatile − Can be easily disconnected from the computer or inserted − It is not directly accessed by the CPU − Suitable example e.g. CD, DVD, USB flash memory − Portable, small − Expensive to buy per GB

Optical- CD, DVD, Blu-ray Solid state- USB flash drive (important to mention flash drive) , SD cards Magnetic- HDD

− Manage input output − Multi-tasking − Loading and running of apps − Manage security − Memory management − Error handling − Human computer interface

High-level − Makes use of words close to human language − Machine independent and portable − Problem and logic focussed − Needs to be translated/interpreter/compiled (to low-level for processing by computer) // needs converting to machine code − Hardware of computer does not matter Benefits − Easy to understand as its similar to human language − Easy to debug, less likely to make mistakes − Less time to write − Has a great range of languages

Low level − Closer to/is machine code − May use mnemonics − May need an assembler to be translated − One line of code represents a single instruction Benefits − Machine dependent − Have direct access to memory locations/registers − May require use of special hardware − Code runs fast Disadvantage −Easy to make errors and hard to understand Examples − Machine code − Assembly

− The structure of language statements in a computer program is called the syntax − A programming language that uses natural language statements is called a High level language − When programs are written in this type of language they need a translator to convert them into machine code − A programming language that is written using mnemonic codes is called assembly language. − This is an example of a low level language

− Programs need to be translated to machine code so we have 3 types of translators − Compiler, interpreter, assembler −Compiler translates high level to machine code − Interpreter translates high level to machine code − Assembler translates low level to machine code

− Translates a whole program in one go − Produces an executable file − All error list produced at the end − Once program is compiled, doesn’t need to be recompiled − One high level statement can be translated into many machine codes − Executable file usually distributed for general use − Executable file does not require to be re-translated

− Translates code line by line − No executable file produced, interpreter required every time − Stops translation when error found, then allows you to continue from where u started − Errors shown in real time, when found, easy to debug − Used in developments of a program or game

− DVD uses red laser/light whereas blu-ray uses blue/violet laser/light − DVD has a smaller (storage) capacity // Blu-ray has a larger (storage) capacity − DVD has two layers (of polycarbonate) whereas Blu-ray disks have a single layer (of polycarbonate) − DVD has a slower transfer rate (of approximately 10 mbps) // Blu-ray has a faster transfer rate (approximately 36 mbps)

• Infra red rays are sent across the screen from the edges • Sensors are around the edges and capture beams • Infra red is broken by a finger blocking it • Calculation is made to locate the touch based on where the beam was broken