Flashcards in Computer Systems Deck (43):
Define the term software.
Comprises all the programs that are written to make computers function.
Define the term hardware.
The electrical or electromechanical parts of a computer, and its input, output and storage device.
Explain what is meant by system software.
Software needed to run the computer's hardware and application programs.
Explain what is meant by application software.
Consists of programs that perform specific user-oriented tasks.
Give examples of system software.
OS, utility programs, libraries, programming language translators.
Explain the need for, and function of operating systems (OS).
Disguises the complexities of managing and communicating with its hardware from the user via an Application Programming Interface (API).
Explain the need for, and function of utility programs.
Makes it easier for the user to use the computer or provides housekeeping functionality.
- Security utilities that keep your data safe.
- Disk organisation utilities that organise your files into folders and tidy up the desk.
- Data compression utilities
- File backup utilities
How does the OS handle management of the processor(s)?
With computers able to run multiple applications simultaneously, OS is responsible for allocating processor time to each one as they compete for the CPU.
While one application is busy using the CPU for processing, OS queues up next process required by another application to make the most efficient use of the processor.
How does the OS handle management of the memory?
When a program is running it must be in the computer's main memory, and the OS must manage where in memory each program and the data it needs will go.
How does the OS handle management of the I/O devices?
When a user gives an instruction to print, the I/O management function takes over + controls the sending of the data to be printed from memory to the device driver.
How does the OS handle management of the security?
- Controlling access to a computer by setting up passwords for different users.
- Setting different access rights + privileges for different users
- Automatically downloading updates for OS to ensure security loopholes are patched
- Encrypting files that are stored on the hard disk
Explain the Von Neumann architecture.
In the Von Neumann Architecture:
- program is stored in main memory + instructions are fetched and executed sequentially.
- there is a single memory (+ bus system) for accessing both data and programs.
Explain the role and operation of the arithmetic logic unit.
The ALU carries out following functions:
-Logical operations: AND, OR and NOT gates
-Shift operations: The bits in a computer word can be shifted left or right by a certain number of places.
-Arithmetic operations: Includes addition, subtraction, multiplication and division.
Explain the role and operation of the control unit.
Coordinates all the activities taking place inside the CPU. Functions:
- Controls execution of instructions in the correct sequence
- Decodes instructions
- Regulates + controls processor timing using regular pulses from the system clock
- Sends + receives control signals to and from other devices within the computer.
Explain the role and operation of the clock.
System clock controls processor timing, switching between zero + one at rates exceeding several million times per second. Synchronises all CPU operations.
- Clock frequency is the number of clock cycles which occur each second.
Explain the role and operation of the bus.
Buses are internal connections that pass data between the components of the CPU.
Data and instructions are passed between registers and other components along these buses.
Explain the effect of the clock speed on the performance of the CPU.
- All processor activities begin on a clock pulse.
- One clock cycle per second = 1 Hz
- Clock speed is measured in GHz = one billion cycles per second
- The greater the clock speeds, the faster instructions will be executed.
Explain the effect of the number of processor cores on the performance of the CPU.
A PC with a multi-core processor, executing many tasks at the same time, will operate faster than a single-core processor.
Explain the effect of the cache type on the performance of the CPU.
Cache makes any type of data frequently used by the CPU available much more quickly. The performance of the CPU increases as the processor has to access main memory less often, so it works faster.
What happens in the Fetch part of the Fetch-Execute cycle.
Address A of next instruction is fetched from the register where it is held. This register is incremented so it points to next instruction to be fetched. Instruction at address A is fetched from memory + put into a special register ready to be decoded.
Explain the differences between main memory and secondary storage.
Main memory is accessed directly by the CPU, ss isn't.
Ss is non-volatile, holds more data + relatively inexpensive per MB.
Ss have slower access speeds than main memory.
Explain the differences between RAM and ROM.
RAM is volatile, ROM is non-volatile.
RAM stores user data/programs/part of OS which is currently in use.
ROM is used to store BIOS/bootstrap loader which is required at start-up of computer.
Memory in RAM can be written to or read from, ROM is read-only.
Why is secondary storage required?
For long term storage - it retains its contents when the computer's power is turned off (including computer's internal hard disk, optical media + solid state disks).
What are the different types of secondary storage?
Solid state drives, optical media and magnetic disks.
Give examples of application software.
Microsoft word, spreadsheet, adobe browser etc
What happens in the decode part of the Fetch-Execute cycle.
The Control Unit decodes the instruction to see what has to be done next.
What happens in the execute part of the Fetch-Execute cycle.
This instruction is executed.
Explain the operation of solid state.
Millions of transistors are either on or off (remain so as long as electricity is applied to system).
SSDs use switches called floating gate transistors. These create a special cage (the gate) that traps the electron flow within it. This gate effect continues whether there is electricity in the system or not, and so storage remains when the power is removed.
Explain the operation of optical storage.
- A low-powered laser reads the disk by bouncing light onto its surface, which is covered in pits + lands.
- Where a pit starts or ends, light is scattered (not reflected well). A land and bottom of pit reflects light well.
- Non-reflective areas = 1s, reflective areas = 0s, only one single track on disk, arranged as tight spiral.
Explain the operation of magnetic storage.
A magnetic disk drive consists of a number of platters (disks) coated in a magnetic material. They spin at around 7200 rpm. The data is encoded into bits and written onto the surface as a series of changes in the direction of the magnetisation. The data is read by detecting the changes in direction.
What are the advantages of solid state?
Doesn't rely on magnetic properties, so unaffected by magnetic fields.
No moving parts so less susceptible to shock + damage than HDDs.
Lighter than HDDs - more suitable for laptops, tablets + other modern devices.
Faster access times than HDDs - don't spin + data accessed instantaneously.
Lower power consumption, battery life extended.
Run much cooler than HDDs (suitable for laptops).
What are the advantages of magnetic storage?
Reliable internal drives
Explain the term 'cloud storage'.
Data is saved in a remote storage facility, + accessed via the internet, e.g. dropbox, google, microsoft.
Explain the advantages of cloud storage when compared to local storage.
Access data from anywhere in the world
Share data with others in different locations
Backup is no longer an issue, responsibility of provider to keep data safe.
What is an embedded system?
Microprocessors/CPUs inside a large piece of equipment, e.g. washing machine, mobile phones, cars and game systems.
Explain how an embedded system differs from a non-embedded system.
System is held in non-volatile memory (ROM or EPROM) + rarely changed during the lifetime of the device.
Some firmware devices are permanently installed + cannot be changed after manufacture.
Not usually possible to upgrade the hardware or attach peripherals.
How does a recordable disk work?
Uses high-powered laser to change the reflecting properties of a disk and thus makes lands and pits.
What is rpm?
Revolutions per minute - measure of speed of rotation.
What are the disadvantages of solid state.
More costly per GB than HDDs.
May deteriorate overtime + not last as long as HDDs.
What are the disadvantages of optical storage?
Can be corrupted or damaged easily by excessive sunlight or scratches.
What are the advantages of optical storage?
Cheap to produce
Easy to send through post (distribution purposes)
Explain the disadvantages of cloud storage when compared to local storage.
Dependant on internet connection to access data
Some users are concerned about security in cloud, whether data could be attacked by a hacker.