Computor Systems Flashcards by Aarya Sumesh

Boolean expressions

Until. Response = N OR response = n

Response = N or N are the expression - used to control loops and if statements

How well did you know this?

Not at all

Perfectly

Boolean variables

Boolean expressions can be given any letter of your choice. The letter is now the Boolean variable
Ie
UNTIL. X OR Y

How well did you know this?

Not at all

Perfectly

Three main Boolean terms

Not
And
Or

How well did you know this?

Not at all

Perfectly

Logic gates are

A symbol assigned to each Boolean term

How well did you know this?

Not at all

Perfectly

Truth tables

Show all possible outcomes of output based on whether input is 0 or 1 ( off or on )

How well did you know this?

Not at all

Perfectly

Logic circuits

Diagram or circuit of lots of interlinking logic gates

How well did you know this?

Not at all

Perfectly

Hardware

Any physical component of the computer

How well did you know this?

Not at all

Perfectly

Software

Any program that runs on the computer

How well did you know this?

Not at all

Perfectly

2 main categories of software are

Systems software & Application Software

How well did you know this?

Not at all

Perfectly

System software description and examples

Programs that are needed to enable the function of the computer are classified under System Software.
Operating System, Utility Software, etc

How well did you know this?

Not at all

Perfectly

Application Software description and examples

Aka APPS

Any program that enables a user to perform a task is classified under this category.
Word, Excel etc

How well did you know this?

Not at all

Perfectly

OS ( operating system) description and examples

Manages the computers resources; manages applications

Processor, memory, input/output, security etc

How well did you know this?

Not at all

Perfectly

Processor management
What is is managed by?
How is it managed?
Example

OS manages processors. In a multi tasking system such as windows, many tasks may be running at the same time. In reality the OS assigns a tiny amount of time to each task in turn.
Eg; person typing document pauses to think, OS will give a new task to the processor

How well did you know this?

Not at all

Perfectly

Memory management description and example

When a program is running it must be in the computers main memory & the OS will many where in memory it must go.
When you start a program the OS allocates the program adequate blocks of free space and allocates memory for any data file you may open.

How well did you know this?

Not at all

Perfectly

Application management description and example

Application programs need the OS to function. When you install an application program the OS will run a program to install it.

How well did you know this?

Not at all

Perfectly

What is the API? Why is it used?

The OS system interacts with applications through the Application Program Interface. The OS needs to communicate with the applications about the execution of modules, saving or deleting data etc

How well did you know this?

Not at all

Perfectly

management of input and output devices description and example

A function of the OS is to control I/O devices. When a user gives an instruction to print a document, the I/O management function takes over & controls the sending of data to be printed from memory to the device driver.

How well did you know this?

Not at all

Perfectly

What is a device driver

Link to HP printers

Each I/O device had a small program that acts as an interface between the device and the computer which is called the device driver
A HP printer would need a different device driver for a Mac and for a PC

How well did you know this?

Not at all

Perfectly

Security management description and example

Many functions to protect device from outside threats or attacks eg
User passwords so files can’t be accessed
Automatic downloads of updates so loopholes are quickly patched
Encryption of files

Embedded systems description and example

Many devices at home use microprocessors or CPUs (embedded systems) to control their functions. They may not need an OS as their tasks are generally simple and repeated

Differences of embedded systems to non embedded systems

System is held in non volatile memory eg ROM or EPROM and rarely if ever changed during the lifetime of the device
Some can not be changed after manufacture unsustainable to attach peripherals

Advantages of embedded systems

Makes device easier to use
Increases reliability 
Enhances usability 
Some connect to WiFi so can record programmes 
Accurate metre bills

Utility software description

Most OS include this even though it’s not essential as it makes it easier for the user
Security utilities ie encryption 
Disk organisational utilities 
Data Compression utilities 
File back up utilities

Encryption software description

Uses an algorithm and key to transform plaintext into ciphertext. Would be necessary to know both the key and algorithm to break it.

Maintenance utilities description

Disk defragmentation - files are stored anywhere on the disk and my be split up. Making the fragments whole again speeds up read access and is more efficient. Automatic updating - mainly useful for security and bug fixes so loopholes are closed.

Compression software description

Size of the file is reduced Lossy- info lost Lossless - just squashed

Von Neumann architecture

Developed the concept of stored computer program in the 1940s The program is stored in the main memory and instructions are fetched and executed re is a single memory & bus system for accessing both data & the program.

Components of the CPU

ALU,CU,Clock and bus

ALU stands for and 3 main functions

Arithematic Logical Unit Logical Operations (AND OR NOT) Shift Operations (bits can shift left or right) Arithmetic Operations

Control Unit

Coordinates all activities taking place in CPU Controls execution of instructions sequentially Decodes instructions Regulates processor timing using regular pulses from system clock Sends and receives control signals

Clock

Controls processor timing Synchronises all CPU Operations Clock frequency is the no of clock cycles per second

Bus

Transports data and instructions between components of the CPU

System bus

Collection of buses or wires connecting the system components

Fetch execute cycle

Fetch Address of the next instruction is fetched from the register. Register is incremental to point to the next instruction. Address is fetched from memory and put into a special register for it to be decoded Then decoded Then executed

What is the register

A fast memory location in the processor

Factors that affect CPU performance are

Clock speed - more cycles per sec the quicker it is processed. 1 cycle per sec = 1Hz 1bn cycles per sec =1GHz Cache memory - memory that needs to be accessed quickly is stored temporarily here to reduce time needed to sort through the disk Core - in theory more processors the better the performance however no viable technology that will process the instructions on multi core sequentially

Put the words main memory, secondary storage, CPU and access in a sentence

Main memory can be accessed directly from the cpu but secondary storage can not

RAM stands for and description

Random Access Memory temporarily holds programs and data whilst they are being executed however nothing can be stored here. It is volatile so memory will likely be lost if power is lost. Purpose is to act as a temporary storage between for programs and data for the processor to access

ROM stands for and description and include info about booting

Read only memory The OS and all programs are stored on HDD OR SSD but have to loaded into RAM to be run Bootstrap loader - small program on comp which loads the OS hence the word bootstrapping became booting Non volatile

Cloud storage Adv Disadvantage

``` Saving data in an off site location controlled by 3rd party provider Adv Back up is responsibility of provider Access anywhere Share data people in other locations Diasadv Dependent on internet connection Security may be an issue ```

Types of secondary storage

HDD,SSD,Optical disks,Magnetic Disks

5 things to consider when purchasing a secondary storage device

``` Capacity Speed Portability Durability Reliability ```

Magnetic disks description Advantages Disadvantages

Reads the disk through drive head which scours and reads the data off the disk Cheap,high capacity, very reliable Not portable, easily damaged

Types of flash memory Adv Disadvantage

USB,SSD mainly used for portable devices Reliable,light,fast,low power consumption Expensive,deteriorate, not long lasting

Types of optical devices. Advantages Disadvantages

CD,DVD,Blue-Ray Used for movies music games Cheap,portable Easily damaged