Topic 7 - Computer organisation and architecture - Complete Flashcards
Define computer hardware?
The physical components of the computer system, which includes digital circuitry.
The processing hardware is necessary to gain a useable output from the system
Define Back store?
Normally a hard disk, which retains the data written on to it after the computer system has been switched off.
Could include other storage devices such as flash memory and removable disks.
Define input devices?
A form of inputting data into a computer. Typically a mouse, keyboard and microphone
Define output devices?
System output can be printed out by the user or displayed on a computer system
Define power supply?
Used to convert alternating current into low-voltage direct current to supply power to the internal components of the computer system
Define main memory?
Stores program instructions and data that are processed by the processor
Define address bus?
Specifies a physical address in main memory and the value that is to be read or written into the address is communicated via the data bus
Define control bus?
Manages data processing.
Sends signals to either write from the data bus to a memory address or a signal to read data from a memory address
Define input and output?
Controls signals received from the processor include input or output requests.
These control signals are then used to connect a system bus to specific I/O devices would input from keyboard and outputs from a monitor.
What are 4 operations processors do? S&S P L C I/O
Sorting & searching data
Performing calculations
Logical decision making
Control input/output and storage devices
Define Von Neumann architecture?
Data and instructions stored in a one memory location.
Data and instructions are transmitted through a shared data bus
Define Harvard architecture?
Data and instructions being stored in separate memories locations.
Instructions are fetched from instruction memory serially and data is fetched when needed by an instruction.
Define addressable memory?
Processor needs to address individual memory locations which have unique numeric codes.
What are the 3 steps taken to select a memory location?
Processor writes the numeric code into the address bus.
Processor sends a request to the control bus with instructions to read or write to the memory location.
The data that is being read or written will be transferred via the data bus.
Define the stored program concept?
Program is stored in main memory and machine code instructions are fetched and executed serially in the processor.
Define arithmetic logic unit (ALU)?
Performs arithmetic and logical operations Such as: - fixed point binary - Floating-point arithmetic - Logical operations (AND, OR, NOT) - Shift operations
Define Control unit?
Is to fetch program instructions from memory, to decode them and to execute them serially.
Define Clock?
System clock sends a signal to all computer components on a regular basis to synchronise all the programs.
Define Register?
A fast memory location that exists in the processor or the I/O controller.
General-purpose and dedicated registers.
Define general-purpose registers?
Can be used to hold instructions and data temporarily
R0, R1, R2…..R16
Define dedicated registers?
Are used by the processor to carry out a specific role.
State the 6 dedicated registers? ACC SR PC MAR MBR CIR
ACC - accumulator SR - status register PC - program counter MAR - memory address register MBR - memory buffer register CIR - current instruction register
Define the accumulator (ACC)?
Special register used as fast temporary storage by the ALU
Define the status register (SR)?
Used to hold status of various flags indicating its status:
positive, negative, carry bit, overflow
Define the program counter (PC)?
Holds the address of the next instruction to be fetched
Define the memory address register (MAR)?
Holds the address of the current instruction being executed
Define the memory buffer register (MBR)?
Holds the instruction from the (MAR) and the associated data
Define the current instruction register (CIR)?
Used to store the instruction that is being decoded and executed
Define the Fetch-Decode-Execute cycle?
This process reads the coded program instructions in the main memory and these instructions are then executed by the processor.
Once the instruction has been executed the process is repeated to read the next instruction.
Define the FETCH part of the Fetch-Decode-Execute cycle?
- (PC) points to next instruction to be fetched
- Contents of (PC) copied into (MAR)
- Instruction in (MAR) transferred via data bus to (MBR)
- Contents of (MBR) copied to (CIR) and (PC) updated to
next instruction
Define the DECODE part of the Fetch-Decode-Execute cycle?
- The instruction in the (CIR) is decoded
Define the EXECUTE part of the Fetch-Decode-Execute cycle?
- The decoded instruction is executed
- The process is repeated.
Define machine code?
Instructions written in binary code that the processor can interpret and execute
Define instruction set?
Is the set of machine code instructions that a particular type of processor can understand and execute
Define Op-code?
Instructions are the part of a machine code instruction that represents a basic machine operation?
Define Operand?
Memory address that forms part of machine code instruction
Define immediate addressing?
Means that the data in the operand is fixed, immediately available for use.
Define direct addressing/absolute addressing?
Means that the code is directly referred to a memory location.
Define assembly language?
Is used to make machine code instructions more understandable by using mnemonic codes.
Define ARM?
Is a load-store architecture meaning that memory can only be accessed by:
- loading from memory into a register
- Storing the result back into memory
Define branching?
Is used for conditional or unconditional statements
Define a label?
Is a sequence of characters that identifies a location in computer source code
Define unconditional branching?
Is a command where each section of code is jumped over, with no conditional testing
Define conditional branching?
Is a command where a section of code is jumped over based on a conditional test
Define logical bitwise operator?
Is where a logical operation is carried out on each column of two operands.
In bitwise operations, the ‘#’ symbol in the instructions below indicates that an operand is a number and so is an example of immediate addressing.
Define logical shift?
Is a bitwise operation where all the bits of an operand are shifted left or right.
After the shift operation is completed the vacant-bit positions are filled with zeros.
Define hardware?
Interrupts occur when devices indicate they need attention, e.g. mouse button pressed
Define Software?
Interrupts occur when programs detect an error or illegal operation
Define interrupts?
Processors have the option to cause an interruption of the normal operation of the system.
What are the 3 interrupt service routines?
Store interrupted task
Interrupt service routine carried out
Continue interrupted task
Define Store interrupted task?
- Current instruction finishes its execution
- Program counter contents stored in memory
- Register contents stored in memory
Define Interrupt service routine carried out?
- Interrupt number examined and source of interrupt
identified - Program counter loaded with start address for
interrupt service routine - Interrupt service routine is executed
Define Continue interrupted task?
- Contents of registers from original task restored to
memory - Program counter contents from original task restored
- Interrupted task countries
Define clock speed?
How many cycles per second the CPU can execute
Define number of cores?
A core is a small CPU or processor built into a big CPU.
Performance improved by increasing number of cores.
Achieved by using a multi-core processor
Define cache memory?
Cache is high-speed memory that is fitted close to or on the processor
Define word length?
The performance of a processor improves with an increase in word length, providing that the word length and data bus are the same size
Processors 32-bit/64-bit
Define address bus width?
The width of the address bus affects the amount of memory that can be read from or written to, allowing more memory to be installed on the system or embedded device
Define data bus width?
The width of the data bus directly affects how much data can be carried on one fetch operation
Define barcode reader?
Represents a code number for a product and is set of vertical lines of different thickness that represent a number.
- Country of manufacture
- Name of manufacturer
- Product code
How does a barcode work?
Scans or reads the barcode by using a visible red light
A light sensor measures the reflected light, where white areas of bar code reflect more light than black areas so creating an analogue waveform of the barcode.
Define digital camera?
Pictures taken using a digital camera are stored on a memory card and can be transferred to a computer
- Connecting the camera to a computer via a USB port
- By plugging the camera memory card into a card
reader
How does a digital camera work?
When a picture is taken the image strikes the camera sensor.
The sensor records amount of light received and converts it into a digital value.
Define laser printer?
Operate on a page at a time and files that require printing are sent to the laser printer using a page description language.
The printer processes the file and creates a bitmap pattern for the page.
Printer laser beam scans along and across the drum inside the printer.
Toner is then fused onto paper by heat and pressure.
Define RFID reader?
Radio frequency identification tags are fixed to products and the tag will be programmed with information.
RFID tags have an antenna that is used to communicate with an RFID reader for tracking purposes.
This code is then decoded and translated into digital data that is interpreted by the computer to identify the information received.
What are the pros and cons of RFID readers?
Pros: RFID tags do not need a power source as the signal from the ‘reader’ energies the passive tag and cause it to transmit its ID code.
Cons: The RFID range is reduced where the tag does not have its own power source.
Define secondary storage?
Are used in computer systems to avoid having re-entered programs and data for processing by storing a non-volatile or permanent copy.
State the 3 secondary storage devices?
Hard disk
Optical disk
Solid-state disk
State the 4 I/O devices?
BDLR
Barcode reader
Digital reader
Laser printer
RFID reader
Define hard disk?
Internal hard disk drive.
Drive consists of a number of metal disks which are coated with special magnetic material.
The disks are mounted on a common spindle and rotate at high speed.
Series of read/write heads move across disk surface to access or store the data on the disk.
The hard disk mounted in a sealed unit connected to a power supply inside computer
What are the pros and cons of hard disks?
Pros: High data transfer rate
High storage capacity
Cons: Hard disk is fixed inside the computer it can be difficult to transfer data to another computer.
Hard disk is fragile
Define Optical disk?
Is a plastic disk with mirrored surface.
Binary data is burned or pressed onto the surface as pits = 0 or lands = 1.
Laser beams used to read data stored on disk, pits and lands reflect different amount of light, can be decoded to binary data.
What are the 3 types of optical disks?
- CD
- DVD
- Blu-ray
What are the pros and cons of optical disks?
Pros: Portable device, cheap
Reasonable storage capacity
Optical drive can read CD, DVD
Cons: Scratch surface and damage it.
Less storage than hard disk.
Access time is greater than hard disks and SSD.
Define Solid-state disk (SSD)?
Flash memory secondary storage.
Non-volatile NAND flash memory with a controller to manage pages.
Flash memory cells are grouped into grid called pages.
A block consists of many pages, pages cannot be overwritten individually.
What are the pros and cons of Solid-state disk (SSD)?
Pros: Perform faster than hard drives, no moving parts, read and write data faster.
Cons: More expensive, smaller capacity
