Data Storage Flashcards
What are the THREE main types of memory?
1) Cache memory
2) Primary memory / Main memory
2) Secondary memory / Auxiliary memory
What is Cache Memory?
Cache is a small, high-speed chunk of memory which temporarily holds some of the date that is most recently used or data most likely to be accessed, which is already being stored in much slower system memory (RAM).
Primary memory vs Secondary memory.
list 5 points each
1) AKA main memory || auxiliary memory/ external memory
2) Data is stored temporarily || permanently
3) Volatile | non-volatile
4) Data is directly accessed by the CPU || not
5) Uses semiconductor chips to store data || uses magnetic disks. (or flash storage or optical storage)
6) Capacity is low || is high.
7) Relatively faster || relatively slow
6) eg: RAM, ROM, Cache || Hard disk, pendrive, CD
RAM vs ROM
4 points
1) Temporary storage || permanent storage
2) Volatile || non-volatile
3) Used in normal operations || used in the startup process of the computer
4) Writing data is faster || is slower
DRAM vs SRAM
Dynamic vs Static RAM
1) Used for main memory || used for cache.
2) Constructed of tiny capacitors || constructed of circuits transistors (flip-flops).
3) Requires recharge every few milliseconds to hold data || only holds data under a constant power supply.
4) Uses less power || uses more power.
5) Inexpensive || more expensive.
What are Registers?
- Registers are the smallest data holding elements that are built into the processor itself.
- These are the memory locations that are directly accessible by the processor.
- It may hold an instruction, a storage address or any kind of data such as a bit sequence or individual characters.
Types:
● Accumulator (AC)- Stores the results of calculations made by the ALU (temporary).
● Program counter (PC)- Keeps track of the location for the next instruction to be dealt with. The program counter then passes this next address to the
memory address register (MAR).
● Memory Address Register (MAR)- Stores memory location for data or instructions that needs to be fetched from memory or stored into memory.
● Memory Data Register (MDR)- Stores data or instructions fetched from memory or any data that is to be transferred and stored in memory.
Draw a diagram of Von Neumann Architecture.
List the components and describe their purpose. (03)
(draw)
1) I/O Interfaces
● The I/O interfaces allow the computer’s memory to receive information and send data to output devices.
● Allow the computer to communicate to the user and to secondary storage devices like disk and tape drives.
2) CPU
● Can be considered the heart of the computing system
● Includes three main components:
1. Control Unit (CU)
2. Arithmetic Logic Unit (ALU)
3. Registers
3) Memory
● The computer’s memory is used to store program instructions and data.
● Consists of many memory cells (storage units) of a fixed size. Each cell
has an address associated with it.
● Two of the commonly used type of memories are RAM (random-access
memory) and Secondary memory
What are the components of the CPU? (03)
Describe their purpose.
1) Control Unit (CU)
● Responsible for decoding the instructions and controlling how data moves around the computer system.
● The execution of each instruction is determined by a sequence of control signals produced by the control unit.
2) Arithmetic Logic Unit (ALU)
● Carries out the calculations and logical decisions required by the program instructions.
● The inputs to an ALU are the data to be operated on, called operands, and a code indicating the operation to be performed; the ALU’s output is the result of the performed operation.
3) Registers (define)
Von Neumann vs Harvard architecture
6 points
1) CPU has a single memory connection. || CPU is connected to data memory and program memory separately.
2) Speed of execution is slower since it cannot fetch the data and instructions at the same time. || faster.
3) Requires less hardware. || requires more hardware (separate data and address bus for each memory).
4) Requires less space || more.
5) Storage space is utilized. || not, (instructions memory cannot use the space of the data memory and vice-versa.)
6) Controlling becomes simpler since only data or instructions are to be fetched at a time. || complex, simultaneously.
What is a HDD?
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage and one or more rigid rapidly rotating platters coated with magnetic material.
HDD vs SDD?
- *Tutorial 05 - Discussion
https: //drive.google.com/file/d/1ov44000f6w0Gk0Ht5siTEAD3PSIegKrp/view?usp=sharing
How can the time needed for a HDD to read or write on a disk be divided? (03)
Explain the process of each task.
1) Seek Time
● On a movable-head system, the time it takes to position the head at the track is known as seek time.
2) Rotational delay
● Once the track is selected, the disk controller waits until the appropriate sector rotates to line up with the head.
The time it takes for the beginning of the sector to reach the head is known as rotational delay.
3) Transfer time
● Once the head is in position, the read or write operation is then performed as the sector moves under the head; this is the data transfer portion of the operation and the time for the transfer is the transfer time.
Draw and name the parts of a HDD.
(draw)
- platter
- sector
- track
- cylinder
- read/write heads
How is data stored on optical devices?
● Optical storage technology uses laser light to store and retrieve data.
● To write data: a laser beam is used to etch microscopic marks on the disk. These marks are called “pits”. The flat surfaces that aren’t pits are called “lands”.
● Each 1 and 0 of binary data is represented by lands and pits on the surface of the disk respectively.
● To read data: another laser beam attached to a sensor is shone on the rotating disk. This beam bounces back either hitting the sensor (land), or missing the sensor (pit).
(((draw)))
● This hit/ miss signal is used to reconstruct the data.
eg: CD, DVD
