Catégorie

Mémoire (informatique)

En informatique, la mémoire est un dispositif électronique numérique qui sert à stocker des données. La mémoire est un composant essentiel, présent dans tous les ordinateurs, les consoles de jeux, les GPS et de nombreux appareils électroniques. Les mémoires sont vendues sous forme de pièces détachées de matériel informatique, ou de composants électroniques. Les différences entre les pièces sont la forme, l'usage qui en est fait, la technologie utilisée, la capacité de stockage et le rapport entre le coût et la capacité. La technologie la plus courante utilise des semi-conducteurs . On distingue mémoire vive, mémoire morte et mémoire de masse. Les capacités de mémoire et la miniaturisation de ses supports ont depuis quelques décennies grandi au rythme de la loi de Moore, laquelle pourrait, éventuellement, être bientôt dépassée, grâce à l'utilisation de skyrmions et d'antiskyrmions pour stabiliser les nanosystèmes spintroniques, au profit du pouvoir de traitement des ordinateurs. thumb|upright|Mémoire vive pour ordinateur VAX 8600 (1986). Il existe différents types de mémoire : Mémoire vive mémoire où chaque information stockée peut à tout moment être consultée, ou modifiée (voir adressage mémoire). La mémoire centrale des ordinateurs est la plupart du temps une mémoire vive volatile bien que le SSD remplisse de plus en plus souvent ce rôle ; Mémoire morte mémoire où les informations sont écrites une fois mais ne peuvent pas être modifiées. Les mémoires mortes sont utilisées par exemple pour stocker définitivement des logiciels enfouis. Mémoire volatile mémoire où les informations sont perdues lors de la mise hors tension de l'appareil. Par opposition, une mémoire rémanente ou non volatile est une mémoire où les informations sont conservées même après la mise hors tension de l'appareil. Les mémoires rémanentes sont utilisées pour les téléphones portables, les autoradios, les GPS, ou les appareils photo numériques. Mémoire flash mémoire rémanente dont le contenu peut être intégralement effacé en une seule opération.

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Exercices associés (29)

Disques en rotation

Two disks A and B of radius R, aligned, can rotate around a vertical axis z inside a container filled with a fluid of viscosity η. The distances between A and B and between A and the bottom of the container are equal to d. The disk B rotates at constant angular velocity ω₀xa0e⃗_(z). At tu2004=u20040 the angular velocity of A is ωu2004=u20040.

What is the moment of viscous forces applied on A at tu2004=u20040xa0?
What is the sum of the moments acting on A when the velocity is ω ? (N.B.: A has two sur

Tapis roulant

xa0 A mass m is on a conveyor on which it is subject to a dry friction force. We note the static friction coefficient α_(s) and the dynamic one α_(d). Moreover, the mass is attached to the wall by a spring of stiffness k, of length at rest l₀, and of negligible mass. We note g the acceleration of gravity.

At the initial time (tu2004=u20040), the length of the spring is equal to l₀ (i.e. the spring is at rest) and the conveyor starts its function. It drives the mass m at a constant velocity v₀

Le yoyo

A yoyo is made up of a disk of radius R and mass M, around which a massless thread is wound up. The thread is attached to the ceiling and remains constantly vertical; gravity acts on the yo-yo which is free to lower down.

Compute the disk’s moment of inertia I around an axis perpendicular to the disk’s plane and going through its center.
Find the acceleration a⃗ of the yo-yo’s center of mass, as well as the thread’s tension T⃗.
A disk’s moment of inertia with respect to its revolution

Potential of a ring and of a disk

a) A thin circular ring of radius R has a uniformly distributed charge Q. Determine the electric potential at a point P on the axis of the ring a distance x from its center, Fig.xa0[fig:rings] (left) (take that potential at the infinity is 0: V(∞)u2004=u20040). b) A thin flat disk, of radius R₀, has a uniformly distributed charge Q, Fig.xa0[fig:rings] (right). Determine the potential at a point P on the axis of the disk, a distance x from its center (take that potential at the infinity is 0: V(∞)u2004=u200

Problème à deux corps, centre de masse

We consider a square plate with side of length a and uniform density. We pierce a circular hole of radius R in the plate such that the distances between the hole’s edge and two adjacent edges of the plate are b and c, with b,u2006cu2004

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Notebooks associés (8)

Voice Transformation Techniques Using Digital Signal Processing

A Gallery of Voice Transformers[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will explore various ways to implement a system that changes the voice of a speaker. Typical applications for these techniques, strictly sorted by plausibility, include international spy missions and prank telephone calls, and devices such as the one displayed here can be easily bought on the web... or in a novelty shop. No description has been provided for t

Block Processing of Audio Files Using Stateful FIR Filters

Block-processing of audio files[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

This notebook shows a simple way to process audio files (in WAV format) in a block-by-block fashion; this is useful in two cases 1. when you want to process a data stream in real time but you can accept a small processing delay; in this case a buffered approach can yield computational gains 2. when you need to process a large file that does not fit entirely into

Advantages of Digital Transmission over Analog Transmission

[1]Paolo Prandoni, [2]EPFL Analog vs Digital Transmission In this notebook we will explore the advantages of digital transmission over analog transmission. We will model the case of transmission over a long (e.g. transoceanic) cable in which several repeaters are used to compensate for the attenuation incurred by the signal. In [1]: import matplotlib import matplotlib.pyplot as plt import numpy as np import IPython from scipy.io import wavfile plt.rcParams["figure.figsize"] = (14,4)

Digital Simulation of Guitar Feedback in I Feel Fine by The Beatles

I Feel Fine, Digitally[1]¶ This notebook is a little musing inspired by the "internal mechanics" of a very famous audio snippet, namely the guitar sound at the beginning of the song "I Feel Fine", written and recorded by the Beatles in 1964. The historical significance of the record lies in the following claim by John Lennon:

 "I defy anybody to find a record... unless it is some old blues
 record from 1922... that uses feedback that way. So I claim it for
 the Beatles. Before H

Understanding the Haar Basis for Grayscale Image Compression

A Basis for Grayscale Images[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

The concept of "basis" for a vector space is one of the most profound and fruitful ideas in linear algebra. Basis vectors are the "building blocks" that all other vectors are built from; by "disassembling" a vector into a linear combination of basis elements we are able to "look inside" the vector and highlight many of its relevant features. A vector space has an infinite number o

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Mémoire (informatique)

Chattez avec Graph Search

Training "Data Organization & Storage Solutions"

A-Scan: Efficient Scale-Up Analytics via Throughput-Guided Data Movement

Roadmap on advanced and / real-time characterisation of solid state materials and devices for energy applications

Training "Data Organization & Storage Solutions"

A-Scan: Efficient Scale-Up Analytics via Throughput-Guided Data Movement

Roadmap on advanced and / real-time characterisation of solid state materials and devices for energy applications