physical devices, to store, sequences of instructions, data, temporary or permanent basis, digitalelectronic device, primary memory, function, access, higher memory capacity, is called, virtual memory, archaic synonym, meaning, addressable semiconductor memory, integrated circuits, silicon-based transistors, used for example, other purposes, other digitalelectronic devices, volatile and non-volatile, flash memory, firmware, typically dynamic, CPU cache memory, energy-consuming, area unit, organized, bistable flip-flops, fixed word length, binary address, raised, implies, registers, addressing mechanism, retain, digital data, fundamental component, central processing unit, manipulates, hierarchy, puts fast, interchangeably, arithmetic logic unit, requires, interface, regular refresh cycles, dynamic RAM, worthwhile, DRAM dominates, kilobytes, vital, failure, lead, viruses, malicious software, cause of bugs, arithmetic overflow, calculation results, allocated memory, signed, result, undesired operation, leak, segmentation fault, tries, access, buffer overflow, breach of system security, vulnerabilities, maliciously exploited
Exercise 2. Find these words and word expressions in the following text. Translate them into Russian. You can use them while retelling the text.
computing, memory, physical devices, store programs, data, digitalelectronic device, primary memory, secondary memory, high-speed function, program and data storage, memory capacity, virtual memory, store, semiconductor memory, integrated circuit, silicon-based transistors, computer, volatilememory, non-volatile memory, flash memory, computer memory, firmware, boot programs, CPU cache memory, bistable flip-flop, one bit per memory cell and multiple bits per cell, binary address, processorregisters, ROM/PROM/EPROM/EEPROM memory, RAM, DRAM, SRAM, fast CPU cache memory, semiconductor memory, tape, magnetic disks and optical discs (CD-ROM and DVD-ROM), computer data storage, recording media, digital data, central processing unit, computations, storage hierarchy, storage options, control unit, arithmetic logic unit, flow of data, arithmetic and logical operations, power, interface, regular refresh cycles, memory chip, desktop system memory, kilobytes, Z-RAM, TTRAM, A-RAM and ETA RAM, read-only memory, FeRAM, CBRAM, PRAM, SONOS, RRAM, Racetrack memory, NRAM and Millipede, operating systems, viruses, malicious software, bugs, programmer, memory leak, buffer overflow, data, space, crash, or a breach of system security
Exercise 3. What do you know about these notions?
Exercise 4. Read the text and answer the questions following it.
TEXT MEMORY
In computing, memory refers to the physical devices used to store programs (sequences of instructions) or data (e.g. program state information) on a temporary or permanent basis for use in a computer or other digitalelectronic device. The term primary memory is used for the information in physical systems which function at high-speed (i.e. RAM), as a distinction from secondary memory, which are physical devices for program and data storage which are slow to access but offer higher memory capacity. Primary memory stored on secondary memory is called "virtual memory". An archaic synonym for memory is store.
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The term "memory", meaning primary memory is often associated with addressable semiconductor memory, i.e. integrated circuits consisting of silicon-based transistors, used for example as primary memory but also other purposes in computers and other digitalelectronic devices. There are two main types of semiconductor memory: volatile and non-volatile. Examples of non-volatile memory are flash memory (sometimes used as secondary, sometimes primary computer memory) and ROM/PROM/EPROM/EEPROM memory (used for firmware such as boot programs). Examples of volatile memory are primary memory (typically dynamic RAM, DRAM), and fast CPU cache memory (typically static RAM, SRAM, which is fast but energy-consuming and offer lower memory capacity per area unit than DRAM).
Most semiconductor memory is organized into memory cells or bistable flip-flops, each storing one bit (0 or 1). Flash memory organization includes both one bit per memory cell and multiple bits per cell (called MLC, Multiple Level Cell). The memory cells are grouped into words of fixed word length, for example 1, 2, 4, 8, 16, 32, 64 or 128 bit. Each word can be accessed by a binary address of N bit, making it possible to store 2 raised by N words in the memory. This implies that processorregisters normally are not considered as memory, since they only store one word and do not include an addressing mechanism.
The term storage is often used to describe secondary memory such as tape, magnetic disks and optical discs (CD-ROM and DVD-ROM).
Computer data storage, often called storage or memory, is a technology consisting of computer components and recording media used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but larger and cheaper options farther away. Often the fast, volatile technologies (which lose data when powered off) are referred to as "memory", while slower permanent technologies are referred to as "storage", but these terms can also be used interchangeably. In the Von Neumann architecture, the CPU consists of two main parts: control unit and arithmetic logic unit (ALU). The former controls the flow of data between the CPU and memory; the latter performs arithmetic and logical operations.
Volatile memory
Volatile memory is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either Static RAM (see SRAM) or dynamic RAM (see DRAM). SRAM retains its contents as long as the power is connected and is easy to interface to but uses six transistors per bit. Dynamic RAM is more complicated to interface to and control and needs regular refresh cycles to prevent its contents being lost. However, DRAM uses only one transistor and a capacitor per bit, allowing it to reach much higher densities and, with more bits on a memory chip, be much cheaper per bit. SRAM is not worthwhile for desktop system memory, where DRAM dominates, but is used for their cache memories. SRAM is commonplace in small embedded systems, which might only need tens of kilobytes or less. Forthcoming volatile memory technologies that hope to replace or compete with SRAM and DRAM include Z-RAM, TTRAM, A-RAM and ETA RAM.
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Non-volatile memory
Non-volatile memory is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory (ROM), flash memory, most types of magnetic computer storage devices (e.g. hard disks, floppy discs and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards. Forthcoming non-volatile memory technologies include FeRAM, CBRAM, PRAM, SONOS, RRAM, Racetrack memory, NRAM and Millipede.
Management of memory
Proper management of memory is vital for a computer system to operate properly. Modern operating systems have complex systems to properly manage memory. Failure to do so can lead to bugs, slow performance, and at worst case, takeover by viruses and malicious software.
Nearly everything a computer programmer does requires him or her to consider how to manage memory. Even storing a number in memory requires the programmer to specify how the memory should store it.
Memory management bugs
Improper management of memory is a common cause of bugs.
In arithmetic overflow, a calculation results in a number larger than the allocated memory permits. For example, a signed 8-bit integer allows the numbers −128 to +127. If its value is 127 and it is instructed to add one, the computer cannot store the number 128 in that space. Such a case will result in undesired operation, such as changing the number's value to −128 instead of +128.
A memory leak occurs when a program requests memory from the operating system and never returns the memory when it's done with it. A program with this bug will gradually require more and more memory until the program fails as it runs out.
A segmentation fault results when a program tries to access memory that it has no permission to access. Generally a program doing so will be terminated by the operating system.
Buffer overflow means that a program writes data to the end of its allocated space and then continues to write data to memory that belongs to other programs. This may result in erratic program behaviour, including memory access errors, incorrect results, a crash, or a breach of system security. They are thus the basis of many software vulnerabilities and can be maliciously exploited.
