B1-05.06.1 BASIC COMPUTER STRUCTURE

• Computers work by manipulating 1s and 0s (binary data)
• Computers translate input data from input devices into output data for output devices
• Complex computers consist of the same combinations of components

Computer Composition

• Computers are centred around a motherboard
• A motherboard contains a CPU, RAM slots, and integrated circuits
• Integrated circuits connect to peripherals (sound cards, graphics cards, speakers)
• Computer outputs vary depending on the software running

Binary Digits and Transistors

• An IC is made of transistors that switch between ON and OFF states
• Transistors are activated by applying voltage to the base
• Computers use two logic levels: ON (1) and OFF (0)
• 1/ON/HIGH is typically about 5V DC, while 0/OFF/LOW is typically 0V DC in electronic components

Bits

• A binary digit (bit) of information is the 1 or 0 applied to the transistors, gates, or integrated circuits
• Computation is performed by processing bits of information
• Electronic components combine to allow bits of information to operate logic circuits

AND Gate

• A transistorised light circuit operates as a simple AND gate
• A 5V DC must be applied to both transistors to switch on the light
• In this setup, logic can be used to perform a function where light only switches on if both inputs are high
• This principle forms foundation of all computer processing

Bits, Nibbles, Bytes

• One bit is not sufficient to carry much information because it only has values 0 and 1
• The total number of states bits can represent increases exponentially as bits are added
• Two bits can represent 4 values: 00, 01, 10, 11
• Three bits have 8 possible values which are 000, 001, 010, 011, 100, 101, 110, and 111
• Four bits have 16 possible values
• Eight bits have 256 possible values
• A nibble is 4 bits of data (1111)
• A byte is 8 bits of data (1111 1111)
• A byte of information can output 256 possible combinations of bits, useful for designing computer components
• A single character on a keyboard is represented internally as a series of 8 bits, or a byte
• Computers store and manipulate bunches of 8 bits of data, known as a byte
• ASCII codes use 8 bits to represent a character
• Computers store and manipulate an individual byte or a group of bytes
• Individual bytes or groups of bytes form the basic unit of memory

Memory Capacity

• Storage capacities are specified in number of bytes
• Modern computing memory is referred to in kilobytes (KB), megabytes (MB), gigabytes (GB), and terabytes (TB)
• The symbol K (kilo) is equal to 1024 bytes
• A computer with 512K bytes of primary storage can hold 512 x 1024 = 524,288 characters (bytes)
• An MB is 1024 KB, and a GB is 1024 MB, a TB is 1024 GB
• 1 terabyte = 1e12 bytes = 1,000,000,000,000 bytes

Integrated Circuits

• An integrated circuit (IC), also known as a microchip
• An assembly of electronic components, fabricated as a single unit
• Logic gates and circuits increase with the number of logic gates and circuits required to represent data
• ICs allow for miniaturized active devices (transistors, diodes) and passive devices (capacitors, resistors) to be combined and allow for complex logic actions
• Integrated circuits eliminate individual electronic components in modern applications
• Integrated circuits contain thousands of transistors, resistors, and capacitors to perform complex tasks (multistage amplification, logic circuits, and computer processors)

IC Advantages

• Drastically reduced size and weight
• Increased reliability
• Lower cost
• Improved performance
• IC packaging is designed to provide distinct inputs and outputs and dissipate heat

IC Disadvantages

• Difficult to repair leading to replacement
• Typically more cost effective to replace than repair

Computer Hardware

• Computer hardware refers to the physical components of a computer, which include:
  • Case
  • Motherboard
  • CPU
  • RAM, ROM
  • Graphics card
  • Sound card
  • Input devices (mouse, keyboard)
  • Output devices (monitor, speakers)
• Includes all physical components and their makeups including circuit components

Computer Software

• Software plays a major role in computer data processing
• Software translates instructions from a human to a computer
• Hardware components exist to run the software
• Through input devices, a computer receives prompts and task direction via software
• Operating systems receive the instructions and processes to allocate memory and run processes

Motherboard Components

• CPUs are connected to motherboards
• Motherboards contain the interconnection circuitry and plug-in points to operate a computer
  • Memory - RAM and ROM
  • Solid state drives
  • Graphics cards
  • Sound cards
  • Memory cards
  • Hard disc and CD drives

Microcomputers

• A microcomputer is an electronic device with a microprocessor as its CPU
• The term microcomputer was a term formerly used for personal computers
• Modern devices that fall under the category of microcomputer are: modern desktop PCs, video game consoles, laptops, tablets, smartphones, smart watches, pocket calculators and industrial embedded systems
• These computers maximize size, performance and memory

Components of a Computer

• The Motherboard contains a bus system (internal and external) and houses other components needed to operate
• The bus system (internal and external) serves as the communication highway of the motherboard
• The CPU performs basic arithmetic, logic, controlling, and I/O operations from the program instructions
• The Main Memory, (known as RAM) stores the programs and data used by the CPU
• I/O Circuitry are the computer peripherals enabling input and output devices
• Graphics Processing Unit (GPU) is an external system used alongside the computer

Computer Processors

• A computer processor comprises circuits designed to produce a particular output for certain inputs
• Calculators are a simple processors designed to perform basic mathematical calculations

Operating Systems

• An operating system manages a computer's resources and operations, also controlling the execution of other programs
• Aircraft systems and components like FMCs and MCDUs use customised operating systems to manage their functions

Memory Technologies

• The CPU must be able to locate each instruction and data item in storage
• Data is held in storage and can be located by knowing its address
• Data storage technologies include:
  • Magnetic core storage
  • Semiconductor Dynamic Random-Access Memory (DRAM)
  • NAND Solid State Drives (SSDs)
  • Magnetic tape storage
  • Magnetic Disc Hard Drives (HDDs)

Magnetic Core Storage

• Magnetic core storage makes up of tiny doughnut-shaped rings made of ferrite (iron) strung on thin wires
• Each ferrite ring can represent a 0 or 1 bit, depending on its magnetic state
• Data is retained if there is a power failure because cores store data in magnetic charges

Dynamic Random Access Memory

• DRAM is a semiconductor memory that stores data in a memory cell (a tiny capacitor/transistor circuit) based on metal-oxide-semiconductor (MOS) technology
• Capacitors represent 0 and 1 data states when charged or discharged
• DRAM requires an external memory refresh circuit because capacitors slowly discharge
• DRAM is volatile memory as it loses data when it loses power

NAND Solid State Drive

• Performance depends on the number of parallel NAND flash ICs used in the device
• NAND SSDs retain data without a constant power supply
• NAND SSDs have a slow leakage date, making them unsuitable for long term data storage

Magnetic Tape Storage

• Another type of storage device is a magnetic tape used mainly for secondary storage
• Magnetic tape is packaged in open reel, cartridge or cassette
• On magnetic tape, 1s and Os are recorded as strings of data (serial access memory)
• For data to be retrieved, the tape must be cycled through to the right position

Magnetic Disc Storage

• Magnetic discs have a direct-access capability
• Magnetic discs come in sizes from 3in to 4ft in diameter
• Magnetic discs are either portable or hard drives

Semiconductor Storage

• Semiconductor memory consists of millions of tiny electronic circuits etched on a silicon chip
• A bit cell is each electronic circuit and can represent a 0 or 1 bit on whether current is flowing
• Fast internal processing speeds
• High reliability
• Low power consumption
• High density
• Low cost
• Silicon memory is volatile and data is lost when no power is applied

Memory Storage Devices

• Memory is a device/system to store information for immediate use
• Term memory is commonly used with primary storage or main memory
• All memory sections contain facilities to store computer data until they are needed

Storage Device Classification

• Memory in computers is classified into short-term data storage and long-term data storage
• The amount of memory installed affects the computer's speed and performance
• Primary Storage is when data can be read from and written to primary storage
• Kinds of memory used within the CPU are:
  • Random-Access Memory (RAM)
  • Read-Only Memory (ROM)
  • Programmable Read-Only Memory (PROM)
  • Erasable Programmable Read-Only Memory (EPROM)
• The two main types of primary storages are ROM, which is non-volatile, and RAM, which is volatile
• Computer primary storage is limited in size compared with secondary storage, which often comes as 4GB, 8GB, or 16GB

Random Access Memory

• RAM is an essential computer component
• Applications store and access data in RAM on a short-term basis
• RAM stores data that computers actively use
• RAM is volatile
• Data in RAM can quickly be accessed before being operated
• RAM is random access memory
• Can directly access any memory cell if you know the row/ column address

Read Only Memory

• Solid-state ROM memory unlike RAM which is usually lost
• Computer manufacturer programs
• Read Only Memory cannot be changed by user

Programmable Read Only Memory

• Program can enter memory using blank PROM
• The disadvantage is that it once written to can never be changed

Erasable Programmable Read Only Memory

• EPROM can be purchased blank and programmed
• EPROM requires separate equipment
• The memory can be erased and reprogrammed

Software Storage Mediums

• Software storage mediums are: reel-to-reel, 8-in., 5 1/4-in. and 3 1/2-in. floppy discs, cassette tapes, CDs, DVDs, portable hard and flash drives
• Flash memory cards are often used in digital cameras and mobile devices
• Memory outside the main body of the computer (CPU) where programs and data for future use is stored is secondary storage
• Secondary storage data does not disappear when there is a power shutoff
• Secondary storage is non-volatile and data is only lost when it is intentionally erased

Aircraft System Applications

• Computer technology improves aircraft safety, reduces pilot workload, economizes operations and controls cabin functions
• Enhancements in navigation, in-flight entertainment and communication software are made by digital computer technology
• Radar detects storm activity and terrain
• A digital processor gathers data to improve the ability for pilots' to monitor and control the aircraft