Computer Systems THEORY flashcards
(38 cards)
Define Hardware.
The physical components that make up a computer system. (e.g. motherboard)
What is a computer system?
The hardware and software working together making up a computer, processing data and completing tasks, allowing users to perform specific tasks.
Define Software.
The programs that run on a computer (e.g. utility software)
Describe what systems software is vs. application software.
SYSTEMS SOFTWARE - The programs that manage/control computer hardware and application software (e.g. operating system).
APPLICATION SOFTWARE - The programs (launched from OS) which help the user perform specific tasks (e.g. word processors).
What is an operating system?
A piece of system software that acts as an interface between the user and the hardware, managing the hardware and all other software (also launching all software).
Describe the roles of the operating system.
- User interface - communicating with the user (sending and receiving instructions to and from applications and hardware).
- Memory management - allocating memory addressed for processes/data.
- Scheduling - scheduling CPU time between programs, allowing multiple to run.
- File management
- Device drivers - OS uses them to communicate with with peripherals (software that translates commands).
- User management - Authentication, passwords, username.
- (Peripheral) I/O device management - moving data to and from secondary storage.
- application management
What is Utility software?
Programs that keep the computer functioning efficiently (e.g. freeing storage space, removing viruses, backing up files).
What are roles of Utility software?
1) Compression - reducing file size so it can be stores using less space/ transmitted quicker.
2) Defragmentation - Moving separate parts of a file physically together, to speed up disk access.
3) Backing up - Creating copies of files on the same disk, back up device or cloud
(Full Backup - copy of all files; Incremental backup - copy of files created or edited since last backup.)
4) Encryption - data scrambling to prevent unauthorised access of files/data. For secure storage/ secure transmission.
Explain Von Neumann architecture.
Von Neumann architecture is a system where both data, instructions (+ programs) are stored in the same main memory. Refer to diagram.
What are the main parts of the CPU?
- Control Unit
- ALU (Arithmetic logic unit)
- Clock
- Registers
- Buses
Describe the roles of the ALU.
- Performing arithmetic operations ( + - x / )
- Performing relational operations ( < > = )
- Performing logical operations ( AND, NOT, OR)
Describe the roles of the Control Unit.
- Managing execution of instructions (by coordination activates of other hardware).
e.g. sending signals to RAM to state whether data should be READ or WRITTEN to from memory.
Describe the roles of the Clock.
- A signal that synchronises tasks (by synchronising all components of the CPU)
- 1 tick of the clock, 1 instructions is processed.
(Clock speed measure in gigahertz)
Describe the roles of the Registers.
- Small areas of memory that hold data and memory addresses used during fetch execute cycle.
Describe the roles of the Buses.
Data Bus - moves data back and forth between CPU and memory.
Address Bus - transmits memory locations.
Control Bus - transmits commands to other components.
Describe the factors that affect CPU performance.
1) Number of Cores
Core - a single unit comprising ALU and Control Unit, which can execute instructions.
(Overhead - time lost to organising which core will follow which instructions, minimal).
2) Clock Speed
Clock Speed - number of clock pulses per second, measured in gigahertz.
3) Cache Size
Cache: Stores copies of data/instructions from RAM which are access regularly.
4) Cache Type
L1,L2 or L3. L1 Smallest fastest, L3 largest, slowest.
What is the Fetch-Execute cycle?
Fetch Execute Cycle - a continual sequence of tasks where the CPU reads instructions stored in the main memory and executes them as required.
Describe and Explain the Fetch Stage in the Fetch-Execute Cycle.
1) There is 1 Clock Pulse.
2) A register (Program counter) contains the location of where the next instruction is to found.
3) The location (Address) is transmitted along the address bus to memory.
4) Memory responds by sending the contents of the address along the data bus back to processor.
(next instruction fetched to the CPU from main memory)
Describe and Explain the Decode Stage in the Fetch-Execute Cycle.
5) The Instruction is read by the control unit, which prepares the register for the type of data it will be storing. It is decoded to work out what it is
Describe and Explain the Execute Stage in the Fetch-Execute Cycle.
6) The instruction is carried out (performing operation, writing to main memory etc.)
7) The Program counter is updated as the current instruction has been executed.
What is an embedded system?
A dedicated system which is part of a larger system. They are computers built into other devices, like dishwashers, microwaves and TVs.
What do embedded systems normally do?
What are the advantages of embedded systems?
- Embedded systems are often used as control systems. They monitor and control machinery in order to achieve a desired result.
- As they’re usually dedicated systems, and only serve one purpose, they are easier to design, cheaper to produce, and more efficient at doing their task than general purpose computers.
What are the 2 types of programming languages?
High Level Languages - more understandable to humans than L.L. (python)
Low Level Languages - hard to understand for humans, easy to execute for computers (machine code, assembly language)
What are the differences between machine code and assembly language? Characteristics?
- processors execute machime code, and each type of processor (or family of processors) has its own specific machine code instruction set
- assembly language is often used to develop software for embedded systems and controlling specific hardware components
- assembly language has a 1:1 correspondence with machine code
