Computer System Fundamentals Flashcards
Describe the function of the address bus and its direction
The address bus carries the address of the piece of memory or I/O device to be read from or written to. It is unidirectional and data travels from the CPU to memory.
Describe the function and direction of the data bus
The data bus carries the data that is to be written or has been read from memory. It is bidirectional and carries data to or from memory.
Describe the function of the control bus
The control bus carries signals that control the actions of the computer. e.g. one line of the control bus may be the read/write line.
Describe the differences and similarities between SRAM and DRAM
DRAM: Must be constantly refreshed, inexpensive to manufacture
SRAM: Does not need to be constantly refreshed, expensive to manufacture
Similarities: Both DRAM and SRAM are volatile
Describe the differences between EEPROM/EPROM and ROM
ROMs are manufactured with the required data stored permanently on them and can never be updated. More modern types of ROM such as EPROM or EEPROM can be erased and re-programmed.
Describe the ALU and its function
The Arithmetic and Logical Unit is a component of the CPU. It carries out the mathematical functions of addition, subtraction, multiplication and division.
Describe the control unit and its function
The control unit is a component of the CPU and regulates the flow of information through the processor. It receives, decodes, stores results and manages execution of data that flows through the CPU. The control unit determines how and when data is processed and ensures that it is sent to the correct components of the computer.
Describe the function of the instruction register
The instruction register holds the instruction currently being executed.
Describe the function of the memory data register
The memory data register (AKA memory buffer register or data buffer) holds the piece of data that has been fetched from memory.
Describe the function of the memory address register
The memory address register holds the address of the next piece of memory to be fetched.
Describe the function of the program counter
The program counter holds the location of the next instruction to be fetched from memory. It is automatically incremented between supplying the address of the next instruction and the instruction being executed.
Describe what the accumulator is and its function
The accumulator is an internal CPU register and is used as the default location to store any calculations performed by the ALU.
Describe the differences between polling and interrupts. State an advantage and disadvantage for each
Polling is the process of cycling round all of the peripherals attached to the computer and asking if they required any attention.
Interrupts are a mechanism for allowing peripherals to signal the CPU when it requires attention.
Interrupts are harder to implement but are more efficient.
Polling is easier to implement but less efficient than interrupts.
Name each operating system layer from the highest layer to the lowest layer
User Interface File Management System Input / Output Memory Management Kernal
Describe the user interface (UI) layer of the operating system and its function
It allows the user to interact directly with the OS.
There are two distinct types of UI: command line interface (CLI) and graphical user interface (GUI).
The objective of a UI is to allow the user to interact with the computer. It must provide a kind of input facility (e.g. keyboard, mouse, joystick) and some kind of output facility (e.g. monitor, printer)
The UI allows the user to load and run programs and controls the interaction between programs and the user. It also allows the user to modify system settings, control system function and request information.
Describe the file management system layer of the OS and its function
The file management system (AKA file system) is the layer of an OS responsible for organising and managing the storage of data on permanent media.
Describe the input / output layer of the OS and its function
The IO layer of the OS controls all physical communication with external devices such as disk drives, keyboard etc. If a higher layer requires access to a device e.g. if the file system wants to read a block from disk, a request is sent to the I/O layer
What is the system attribute
It defines a file that can only be accessed or used by the OS
What is the read-only attribute
When set, a file cannot be changed, saved or deleted
Describe what happens during an interrupt
Processor acknowledges the interrupt
Processor completes the current instruction and stores the internal register values
The address of the interrupt service routine (ISR) is found in memory
Control is passed to ISR which runs
Internal register values are restored and processor continues with the process which was interrupted
How is the IO interface informed when a transfer is complete
It is informed by a flag signalling
Give two examples of what real-time systems may control
Aircraft, industrial robots
What is ASCII
A 7 bit code representing all printable and non-printable characters
What two things prevent users from updating files that are already open
File locking, block locking
Name two application extensions
.doc, .pdf
Name two executable extensions
.exe, .com
What is unique about TSR antivirus
TSR (Terminate and Stay Resident) stays resident in memory after it has finished running
What does risc stand for
Reduced Instruction Set Computer
Describe two features of a worm
Type of trojan, self replicating without need for other programs
How many bytes long is a sector
512
What is a group of sectors called
A cluster
Where is the OS resident at all times when the computer is on
Main memory
What type of file is used in the automatic installation of an OS
An answer file
What two layers of the OS are responsible for handling paging
Memory management and the kernal
Name two integral OS tools
Defragmenter, formatting
Describe how co-operative multi-tasking differs from multi-tasking
Processes voluntarily suspend themselves in co-operative multi-tasking
Describe PROM
PROM chips can be bought in a blank state and programmed using a prom programmer, however, you can only write onto them once
Describe DMA
Direct Memory Access is a method that allows an I/O device to send or receive data directly to or from main memory, bypassing the CPU to speed up memory operations. The process is managed by a chip known as a DMA controller.
Describe Thrashing
When a hard drive is being overworked by moving information between the system memory and virtual memory excessively, causing the performance of the computer to degrade
