Section 4 - Computer systems Flashcards
Construct an AND truth table. And describe what the logic circuit symbol looks like
A B Q 0 0 0 0 1 0 1 0 0 1 1 1
Circuit looks like a D
Construct an OR truth table. And describe how the logic circuit symbol looks.
A B Q 0 0 0 0 1 1 1 0 1 1 1 1
Circuit symbol looks like a D but instead of a straight edge, it is curved like so )
Construct an XOR truth table. And describe how the logic circuit symbol looks.
A B Q 0 0 0 0 1 1 1 0 1 1 1 0
Circuit symbol looks like an OR gate with an extra ) line
Construct a NOT truth table. And describe how the logic circuit symbol looks.
A Q
0 1
1 0
Circuit symbol looks like triangle with circle at the front
What are the boolean operators for the logic gates?
. to represent an AND gate
+ to represent an OR gate
+ with a circle around it to represent XOR gate
Overbar to represent NOT gate
Explain what is meant by an:
- – application software
- – system software
Application software:
— Apps used for the user benefit e.g. word processor, presentation, games etc.
System software:
— Things that are required for the hardware to operate e.g. OS, utility software, encryption software etc.
What are the functions of the operating system?
- – User interface: an environment that allows the user to interact with the machine e.g. CLI and GUI
- – Security management: security through user accounts and passwords
- – Input / output device: manages the device drivers to convert between the peripheral signals and OS
- – Application management: manages applications installed
- – Memory management: allocates memory blocks in RAM
- – Processor management: allows the OS to multitask so more than one program can run at once
What are the utility softwares?
- – Disk defragmentation software: takes fragmented segments and rearranges them so that computer performance is faster
- – Encryption software: disguises the contents of the files using an encryption key
- – Data compression software: reduces the file size because smaller files are easier to transmit
- – Backup software: makes a copy of files locally and remotely then backs up data to prevent data loss
What are the main differences between low level and high-level language? Give some advantages and disadvantages.
Low-level languages are often written in binary format which makes high-level languages easier to read and understand as they are written in English/normal languages that humans can read.
High-level languages are easier to learn and faster to program. Also, it allows the program to be debugged and maintained better if there are any errors. However an advantage of a low level is that code is written specifically for the processor therefore it stores less memory and executes the program faster.
High-level languages are portable as they are not specific to one hardware.
What are the examples of low-level language? Explain the difference between them.
Machine code:
- – Written in binary specific for the processor as each processor has its own specific machine code instruction set
- – All languages have to be converted into machine code before being executed by the processor
Assembly code:
- – Written using mnemonics and binary in the form of opcode and operand.
- – Opcode tells the instruction and operand tells the data to execute with the instruction
- – Needs to be converted into machine code
- – Used in embedded systems
What are the three different translators? Explain each in detail.
Assembler:
— Translates assembly code into machine code
Interpreter:
- – Translates high-level code line by line into machine code.
- – If code wants to be transported then the source code will be transported as well as machine code
- – Takes a long time as it is done line by line
- – Customers require the interpreter to be downloaded for the software to run
Compiler:
- – Scans high-level source code then translates it all at once into machine/object code
- – If it wants to be distributed then the source code is not seen by customers
- – Error message displayed at the end so it is difficult to find the exact location of the error
- – Compiler does not need to be installed to run the software
Explain the different types of memory within a computer.
Main memory:
- – RAM (random access memory) and ROM (read-only memory)
- – RAM is volatile as it loses its contents when power is lost
- – ROM is non-volatile as it does not lose its data when power is lost
- – RAM is used to store general programs being executed and their data. Loads from the hard disk
- – ROM is used to boot up the contents of the computer as it stores the BIOS/BOOTSTRAP loader
Cache:
- –Faster than main memory but smaller than main memory
- – Stores frequently used data
- – Closer to the CPU so that data can be fetched and exceuted faster
Registers:
- – Located inside the CPU
- – Smaller in size than cache but way much faster
What is secondary storage and how do all the different types work?
Secondary storage is a non-volatile form of memory that is not directly accessible by the CPU.
Optical:
— A laser is shone onto the pits and lands to read the disk as a series of 0s and 1s. The light reflects off lands and is refracted off a pit.
There is one singular track on an optical disk
Magnetic:
— A hard disk uses rotating platters coated in magnetic material. The iron particles are polarised to either become a north or south state which is represented as a 0 or 1. The disk is also divided into tracks which are further divided into sectors. As the disk spins, the read/write head moves back and forth on the disk to read or write data to the disk.
Solid-state drives:
— They use flash memory. Built from transistors and logic gates which do not lose their contents when power is lost
Explain how you would choose a storage device.
HINT: use words like capacity, durability, portability, reliability, speed, cost
Magnetic:
- – Relatively cheap
- – Large capacity
- – Reliable but not durable as there are moving parts
- – Not portable
- – Can be noisy and generate heat
Optical:
- – Small capacity
- – Reliable but easily scratched so not as durable
- – Very portable
Solid State Drives:
- – Quite a small capacity
- – Very fast
- – Quite expensive for small storage
- – Very durable and reliable as no moving parts
- – Easily portable
- – Silent
Give a summary of the advantages and disadvantages of the three secondary storage.
Magnetic advantages:
— Inexpensive, high capacity, very reliable
Magnetic disadvantages:
— Moving parts make it more susceptible to damage, not very portable
Optical advantages:
— Inexpensive, fast access speeds, very reliable, easily portable
Optical disadvantages:
— Small capacity, easily susceptible to damage due to sunlight or scratches
SSD advantages:
— Easily portable, fast access speeds, very durable and reliable
SSD disadvantages:
— Quite expensive for small capacity and does not last as long as a hard disk
