Unit 4 Computer Systems Flashcards
1
Q
Binary logic - AND Gate
A
- If both inputs are 1 (True) then the output is 1 (True)
- Otherwise the output is 0 (False)
2
Q
Binary logic - OR Gate
A
- If either input is 1 (True) then the output is 1 (True)
- Otherwise the output is 0 (False)
3
Q
Binary logic - NOT Gate
A
- If the input is 1 (True) then the output is 0 (False)
- If the input is 0 (False) then the output is 1 (True)
4
Q
Binary logic - XOR Gate
A
- If just one input is 1 (True) then the output is 1 (True)
- Otherwise the output is 0 (False)
5
Q
What does a dot symbol placed at the end of any logic gate mean?
A
Acts as both the gate and a NOT gate combined.
6
Q
Explain the definition of hardware.
A
The physical components that make up a computer system.
7
Q
Explain the definition of software.
A
- Software is the non-physical programs that are stored by and run on a computer system
- Software makes use of physical hardware components and devices as the way of: taking inputs from users, outputting information to users, storing information
8
Q
What is an operating system?
A
A group of programs that is essential for managing the computer’s resources. They are responsible for managing: processor(s), memory, input/output devices, applications, security
9
Q
Explain the term multi-tasking.
A
Where an operating system manages many tasks happening at the same time
10
Q
What are interrupts?
A
- Signals sent to the CPU by external devices to indicate an event that needs immediate attention
- They tell the CPU to suspend its current activities and execute appropriate instructions
11
Q
What is the difference between hardware and software interrupts and give examples?
A
- Hardware interrupts are generated by hardware devices e.g. printer run out of paper
- Software interrupts are generated by programs e.g. a divide by zero error will cause an error message to be displayed
12
Q
Describe the process of memory management.
A
- To run a program, a computer must copy the program from storage into main memory
- Data used by the program is copied into main memory
- The operating system keeps a record of where each program and its data is located
- The operating system will make sure not to overwrite existing programs and data
13
Q
Give some examples of peripheral devices.
A
Mice, keyboard, printers, displays, digital cameras, and graphics tablets
14
Q
What is a device driver?
A
- A program that controls peripheral devices.
- Each device communicates with the OS via its own driver
15
Q
Explain the process of operating system application management.
A
- The operating system (OS) provides graphical user interface (GUI) features such as windows, maximize, minimize, resize
- When an application is opened the OS will copy the program into RAM and allocate an area of RAM for the program to use
- When an application is closed the operating system will make sure that it is removed from RAM
- The operating system may also be responsible for installing and updating applications
16
Q
What security features do operating systems often contain?
A
- User management with usernames and passwords
- Access rights to files, programs and services
- Encryption of hard drives and removable media
- Memory protection : prevention of programs being able to view or overwrite other programs stored in the RAM
- Security updates are automatically downloaded and installed
17
Q
What is utility software?
A
Small programs that perform extra functionality and housekeeping tasks that keep computers running efficiently
18
Q
What is encryption software?
A
Used to encode text so that it cannot be understood without knowing the key to decode it
19
Q
How do you know if a connection to a website is encrypted?
A
Web browsers usually show a padlock for sites that are using HTTPS (Hypertext Transfer Protocol Secure)
20
Q
Describe 4 uses of encryption software utilities.
A
- Encrypt entire hard disks so that the data cannot be understood if the computer is stolen
- Encrypt files and folders on a portable disk such as USB removable storage
- Encrypt communication with websites
- Encrypt data in an organisation’s database, especially sensitive data such as passwords
21
Q
What is disk defragmentation?
A
- When you save a large file it may not fit on the disk in consecutive memory locations
- The file is referred to as ‘fragmented’
- Defragmenting the hard disk reorganises files so they are stored together
22
Q
Types of memory and storage that are used in computer systems
A
- CPU registers
- Cache
- RAM
- ROM
- Secondary storage
23
Q
Function of the clock
A
Controls the timing of the processor. It switches between 0 and 1 several million times per second and synchronises all CPU operations
24
Q
What is a high level programming language?
A
A language that is closer to natural language, such as speaking English
25
What is a low level programming language?
A programming language that is close to the language that machines understand
26
What is RAM often referred to as?
Main memory, primary memory, primary storage
27
Why is RAM called Random Access Memory?
The name comes from the ability of the CPU to access any part of the memory in the same amount of time
28
What does RAM normally store at any one time?
- The operating system (or part currently in use)
- The software currently in use
- The data which the software is using
29
Properties of RAM
- It can be read from and written to
- Access to RAM is much faster than a hard drive
- RAM is volatile, loses data if the power is off
30
What is the difference between storage and memory?
- Storage permanently keeps the data that is currently being used, so if the computer were to turn off data in storage is not lost.
- Memory stores data currently being used temporarily as it is volatile, so if the computer turned off, data stored in memory would be lost forever.
31
Function of a compiler
Translates a high-level language into machine code
32
Function of an interpreter
Another type of program that translates a high-level language into machine code
33
Function of an assembler
Translates assembly code to machine code
34
What is the purpose of the CPU?
To fetch and execute instructions stored in memory
35
Describe Von Neumann architecture.
- Program instructions and the data the programs are using are both stored in the same memory
- The CPU accesses both instructions and data from the same RAM
36
What are the two major components of the CPU, and what is the purpose of each?
Arithmetic-Logic Unit (ALU) - carries out arithmetic and logic instructions
Control Unit - coordinates the CPU activities
37
Function of registers
A special fast memory location in the CPU. Stores small amounts of data, results of calculations, and instructions that the CPU is operating on
38
Function of the Control Unit
Coordinates and controls all the activities taking place within the CPU
- It decodes instructions and executes them
- It receives signals from the system clock
- It directs the timing and control of other parts of the CPU
39
Describe the three buses that make up the system bus.
ADDRESS BUS - stores the address of the memory or device controller to be read from or written to
DATA BUS - carries data throughout the computer system
CONTROL BUS - uses control signals to control all activities within the CPU
40
Purpose of the cache
Stores recently used data and instructions in memory that is faster to access than RAM
41
What affects CPU performance and how does it affect it?
CLOCK SPEED - the faster the clock speed, the faster the instructions are processed
CACHE SIZE - the bigger the cache, the less time a processor has to wait for instructions to be fetched
NO. OF CORES - the more cores a CPU has, the greater the number of instructions it can process in a given space of time
42
What is secondary storage?
Storage that is not directly accessible to the CPU. It is non-volatile.
43
What is data rate?
The rate at which data can be accessed.
44
Examples of non-volatile storage
USB stick, SD card, Blu-ray, CD/DVD, Hard Disk Drive (HDD), Solid State Drive (SSD)
45
Uses of secondary storage
- Programs and data are stored on hard drive
- Blu-rays may be used to distribute films
- Memory sticks may be used to transport data from one place to another
- Magnetic tape or external hard drives may be used for backup
- SD cards can be used for additional storage on camera and smartphones, this is used for music, video and photos
46
Storage methods - solid state
Data is recorded onto solid memory chips without any moving parts
47
Storage methods - optical
Lasers read and write data using light
48
Storage methods - magnetic
Mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape
49
Advantages of magnetic storage
- They are a very cheap form of storage compared to solid state drives
- They have a very large storage capacity, up to 6TB or more
- Relatively fast write speed
50
Disadvantages of magnetic storage
- Lots of mechanical parts
- Issues with durability, fragile
- Sealed unit due to disk head and platter precision
- Not very portable
51
Uses of magnetic storage
- Personal computers
- Storage of large quantities of data
52
Capacity of magnetic storage
500GB - 12TB or greater
53
Advantages of optical storage
- Cheap
- Very easily portable
- Takes up little space physically
54
Disadvantages of optical storage
- Less storage capacity compared to other types
- Easily damaged/scratched
- Requires a CD reader
- Slow write speeds
55
Uses of optical storage
- Songs
- Videos and other multi-media storage
- Backup and archiving of data
56
Capacity of optical storage
CD-ROM - up to 720 MB
DVD - up to 8.4 GB (dual layered disk)
Blu-Ray - up to 50 GB (dual layered disk)
57
Basic features of optical storage
- Data is stored as pits and lands burnt or pressed into a spiral track circulating outwards from the centre.
- A laser beam passes over the pits and lands, the level of reflection is measured
- From this signal, 0s and 1s can be derived
58
Basic features of magnetic disks
- Disk contains concentric circles called tracks
- Each track is divided into sectors
- Disk heads mounted on mechanical arms read and write the data
A disk with a solid platter is a 'hard' disk. Soft plastic disks are known as 'floppy' disks.
59
Why are the capacities of these discs different given they are all the same physical size?
- A CD has bigger pits and lands as red light has a larger wavelength
- The smaller Blu-ray pits and lands allow it to store more data
60
Basic features of Solid State Drives (SSD)
- Solid-state drives use non-volatile flash memory to store information
- Large electric current used to force electrons through a barrier and trap them on the other side
- They remain on the other side until 'flashed' with a new current, hence the name
- Trapped (charged) electron = 0 not trapped = 1
61
Advantages of SSDs
- Highly durable
- No moving parts
- Very fast read/write speed
- No noisy fan or drive arm
- Faster start up times
62
Disadvantages of SSDs
- More expensive than magnetic disks
- Similar storage capacity as magnetic disks
63
Uses of SSDs
- Higher end computers
- Laptops
- Smartphones and tablets
64
What is the capacity of a storage device?
How much data can be stored.
65
What is the speed of a storage device?
The rate (usually in MB/s) at which data can be read or written
66
What is the portability of storage devices?
How easy it is to carry/transport
67
What is the durability of storage devices?
How easily damaged it is
68
What is the reliability of storage devices?
How likely it is to lose the data
69
What is the cost of storage devices?
Price per unit of storage
70
Cloud storage
- Refers to saving data in an off-site storage system maintained by a third party e.g. Dropbox, Google Drive or Amazon Web Services
- Data is saved to servers at a remote location
- These servers can use magnetic and/or solid-state storage
- The data is accessed via the Internet
71
Advantages of cloud storage
- Easy to use, most companies offer apps for desktop and mobile devices to manage their data
- Companies offer a high data storage capacity
- Convenient to use, users can access data from anywhere with an Internet connection
- Backups are carried out by the cloud provider so save the need for local backups
- The data storage capacity can be increased easily as users need more
72
Disadvantages of cloud storage
- The data cannot be accessed without an Internet connection
- A company needs to trust that the security of the cloud service is enough to stop a data breach, they won't be directly able to control the security of the data
- Uploading and downloading data could take a long time and is dependant on the available bandwidth of the user's connection
73
Parts of a hard disk
- Magnetic platter contains data
- Drive read/write head reads data on the drive
- Actuator moves the read/write arm
- Drive spindle rotates
74
Logic circuit
A method of showing Boolean logic in a diagram using a set of symbols called logic gates
75
what is application software?
Any program that is designed to enable the end user to perform a task
76
System software
Provides a platform to run programs which maintain the computer system
77
Primary storage
The memory in which the computer can store data or instructions that are currently in use. The two main types of primary storage is:
- Random Access Memory (RAM)
- Read Only Memory (ROM)
78
Embedded system
A computer system which is built into another device to support its operation
79
What does it mean for a language to be portable?
It can run on different types hardware
80
Advantages of using low-level languages
- Need less translation, and often lead to faster code which is useful for computers with low specifications such as embedded systems
- Provide exact control over the CPU
81
Compiler vs Interpreter
Compiler
- Translates a high-level language program in one go to produce source code
- A compiled program executes faster as it is already in machine code
- Produces an executable file so the original code does not need to be compiled again
- No need for the compiler to be present when the object code is run
Translater
- Translates and executes one line of a high-level language program at a time
- Takes more time to execute as each instruction is translated before it is excepted
- Original code will be interpreted or translated every time it is run
- The interpreter must be installed to run the program
82
Fetch-Decode-Execute Cycle
The CPU operates by repeating three operations:
- FETCH, causes the next instruction to be fetched from main memory
- DECODE, decodes the instruction to work out what the instruction is
- EXECUTE, the instruction is executed
This process is then repeated
83
Embedded systems usually avoid using hard disks in favour of flash memory. Why is that?
Moving parts a less reliable then solid state components which are also more robust
84
System bus
The collection of wires or buses connecting the system components
85
Advantages of an interpreter
- Interpreters will stop as soon as they encounter an error, this is useful for debugging
- Interpreted languages are 'portable', this means that they can be used on many different types of CPU as long as there is an interpreter available for the platform
86
Disadvantages of an interpreter
- Running an interpreted program is slower than running a compiled program because each line needs to be translated every time the software is run
- Interpreters do not produce a compiled program file, the process must be repeated each time the program is run
87
Data compression software
- Utilities such as WinZip enable users to compress and decompress files or folders
- This reduces the amount of storage space needed on a disk
- If sending files, it reduces the amount of data that is sent
- Compression may allow attachments to be sent via email that would otherwise have been larger than a file-size limit
- More data can be stored on backup media
88
What type of storage device are you most likely to find in a mobile phone?
Solid state, as there are no moving parts it's a lot more durable and less prone to damage e.g. phone being dropped
89
Why does a computer need secondary storage?
- Secondary storage is a permanent store of programs and data
- They cannot be held permanent in the RAM because it is volatile and relatively small
- They can be held in ROM for embedded devices, but ROM cannot be updated as it is read only
90
Why does increasing the clock speed of a CPU increase performance?
More instructions can be fetched, decoded and executed in the same amount of time
91
Give three reasons why some programmers still use low-level languages
- They may need to have greater control over the program in order to make a program with lower memory use
- They may need to have greater control over what the CPU does in order to make the program run quicker
- They may be trying to maintain old code or hardware
92
Explain why programmers might prefer to use an assembly language over machine code
Assembly languages are more readable for humans than machine code so can be programmed and edited more easily
93
State two reasons why computers have more RAM than cache memory
- RAM stores the operating system and software currently in use so more is needed for a larger storage capacity
- Cache is more expensive than RAM
94
Explain why solid-state storage is not fitted to every new computer
- Solid-state storage is expensive
- Has relative lower storage capacity than magnetic storage
