Computer Systems Flashcards
What are the units of storage?(7)
- Bit = binary digit
- Byte = a group of 8 bits
- Kilobyte (Kb) = 1,024 bytes
- Megabyte (Mb) = 1,024 kilobytes
- Gigabyte (Gb) = 1,024 megabytes
- Terabyte (Tb) = 1,024 gigabytes
- Petabyte (Pb) = 1,024 terabytes
How are positive numbers stored in a computer?
Binary
How are integers stored in a computer?
How does it work?
Two’s compliment
The most significant bit (128) is made negative
What are real numbers?
How are real numbers stored in a computer?
What is the advantage?
Disadvantage?
Positive, negative numbers including fractions and decimals
Through floating point notation, where the decimal part is the mantissa and the fractional part is the exponent.
It allows very large and very small numbers to be stored in a fewer number of bits
Accuracy is lost since the mantissa gives the number rounded to a certain number of significant figures.
What increases the accuracy of floating point numbers?
What increases the range?
Increasing the number of bits assigned to the mantissa
Increasing the number of bits assigned to the exponent
What is ASCII?
How does it store characters in a computer?
What are control characters?
What is Unicode?
An 8 bit code that can represent 256 characters
Each character is assigned a number from 0 -255 (8 - bit code)
RETURN and TAB
A 16 bit code that can represent many more characters
What is the advantage of Unicode over ASCII?
Disadvantage?
Unicode can store many more characters in different languages so more people all over the world can use it
Unicode requires more storage
What are bit mapped graphics?
How much is each pixel worth
Advantages? (2)
Disadvantages? (4)
A 2 dimensional array of pixels stored in a binary code where 1’s represent black pixels and 0’s represent white pixels
1 bit
Advantages
- Can be edited at pixel level so that fine detail and irregular shapes can be produced
- Good for editing photographic images captured by a digital camera
Disadvantages
- File size can be very large because each pixel must be stored
- The resolution of the image is fixed so when enlarged it becomes jagged
- Parts of the image cannot be separated
- No advantage is gained from sending the image to a high resolution device such as a printer because the resolution is fixed
What are vector graphics?
What are the advantages? (4)
Disadvantages? (1)
Stores an image as a list of objects and their attributes eg.
Advantages
- File size is smaller than bit mapped graphics because only a description is stored
- Editing can be done on each object at an attribute level eg. change the length
- Overlapping objects can be separated again
- Resolution is not fixed so when enlarged the shapes do not become jagged
Disadvantages
1. Not suitable for creating and editing images with fine detail such as photographs taken by a camera. More suitable for shapes
What are the parts of the CPU?
What are the parts of the processor?
What are the parts of the main memory
A processor and main memory
Control unit
ALU
Registers
RAM / ROM
What is a peripheral device and what does it do?
Give examples of:
Input
Output
Backing storage
Any device that can be attached to the CPU for input, output or backing storage
Input = keyboard, scanner, digital camera
Output = printer, projector
Backing storage = CD, hard disc drive, USB memory stick. These are used to permanently store program and data files
What is the function of the:
Control unit
ALU
Registers
CONTROL UNIT-
Fetches and executes the program instructions stored in the main memory one at a time
ALU
Preforms arithmetic operations
Registers
Used to store items of data the the proces is currently working on
What is main memory?
RAM?
ROM?
Used to store the programs and data currently being executed by the processor
Used to temporarily store the programs currently being executed by the processor. Loses contents when computer is switched off. Contents can be changed.
Used to store programs that stay the same. Keeps contents when computer is switched off. Cannot change contents.
What is the address?
What are processor buses?
What are the three kinds?
A unique code used so the processor can identify each location.
A set of parallel wires used to connect the processor and main memory
Address bus = used to specify which memory location is to be used to read or write data
Data bus = used to carry data from a memory location to the processor and vice verse
Control bus = used to send out signal to initiate events
What is machine code?
Why are high level languages much easier to read and find errors than low level languages? (5)
Give some examples of high level languages
The computers own language using binary codes to represent instructions and data. Low level language. Very difficult for humans to write and find errors
- They use English command words
- Complex mathematic equations can be performed in one instruction
- One high level instruction is the equivalent of many machine code instructions
- They have in built functions
- The program can be broken down into procedures
Scratch, Visual Basic and python
What must happen to a high level language before it can be run?
How is this done?
It must be translated into machine code
Using a translator. It translates the high level language (source code) into machine code (object code)
What does a compiler do?
What are the:
- Advantages (4)
- Disadvantages (1)
Translates the program into machine code before the program is run
Advantages-
- Runs fast since there is no translation at run time
- Produces a stand alone program which runs by itself without the need of a compiler or source code in the memory
- Uses less memory
- The source program will only be used again if the program needs changed
Disadvantages-
1. Errors are only identified once the program has been compiled. Once corrected they need to be compiled all over again
What does an interpreter do?
What are the:
- Advantages (2)
- Disadvantages (2)
Translates and executes the program one statement at a time while the program is run
Advantages-
- They are easier to edit since the program will run up to the point of error, be corrected and run again immediately
- It is simpler and less expensive
Disadvantages-
- It will run slower as the statement need to be translated and executed as the program is being run
- The interpreter and source code must be in memory when the program is executed, therefor it requires more memory
What is carbon footprint?
A term to describe how much carbon dioxide is produced in the making and use of electrical goods
What can be done to reduce the amount of power being used by your monitor? (3)
- Brightness levels can be turned down or set to an appropriate level to the brightness of the environment
- Monitors can be set to automatically go to sleep mode after a set period of time
- Remove any used peripheral devices
What happens when a computer is shut down?
Why is this not always good?
What is a more efficient way of saving power?
All of it’s programs and data are closed. The computer now uses almost no power. Some components such as an internal clock may still use up very small amounts of power.
When you want to go on the computer again, you have to restart everything which takes a lot of time.
Stand by/sleep mode. This is when the computer enters a low power state, which keep the data in memory but other parts of the computer are switched off and wont use any power. When the computer is turned back on it takes almost no time at all and the user can begin again where the left off.
What is a firewall?
What is encryption?
A barrier to control network traffic in and out of an organisations network. Data is passed over the internet in blocks of data called packets. The firewall protects a computer system by filtering out any unwanted packets. It inspects it’s contents and sees if they should be aloud through of not. Firewalls also control which internet sites a compute can access.
Data is encrypted by an encryption key, into a code that can only be decrypted with the correct key. Details such as passwords and credit card details are usually encrypted.
What increases power consumption?
Peripheral devices
What harmful chemicals are contained in computers?
What can help to reduce these harmful chemicals being let out into the air?
Mercury, lead and cadmium
Recycling of materials
How do computers increase carbon footprint? (2)
How do they decrease carbon footprint? (2)
- The making and use of computers uses energy is which is produced by burning fossil fuels, which releases carbon dioxide
- They are made of plastic, glass and steel which produce harmful chemicals
- They allow people to work from home and not use trains and buses which burn fossil fuels
- Saves people printing things out and using paper, which saves trees and means there is more intake of carbon dioxide
