Lesson 2 - Software and Hardware

clock speed

The operating speed of a computer or its microprocessor, defined as the rate at which it performs internal operations and expressed in cycles per second (megahertz).

multiprocessing

The running of two or more programs or sequences of instructions simultaneously by a computer with more than one central processor.

byte

A group of binary digits or bits (usually eight) operated on as a unit.

motherboard

A printed circuit board containing the principal components of a computer or other device, with connectors into which other circuit boards can be slotted.

register

A processor register (CPU register) is one of a small set of data holding places that are part of the computer processor. A register may hold an instruction, a storage address, or any kind of data (such as a bit sequence or individual characters). Some instructions specify registers as part of the instruction.

multithreading

A technique by which a single set of code can be used by several processors at different stages of execution.

circuit board

A thin rigid board containing an electric circuit; a printed circuit.

system unit

A typical desktop computer consists of a computer system unit, a keyboard, a mouse, and a monitor. The computer system unit is the enclosure for all the other main interior components of a computer. It is also called the computer case, computer chassis, or computer tower.

arithmetic/logic unit (ALU)

A unit in a computer that carries out arithmetic and logical operations.

execution cycle (E-cycle)

An instruction cycle (sometimes called a fetch-decode-execute cycle) is the basic operational process of a computer. It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction dictates, and carries out those actions.

cache

High-speed RAM (random access memory) that serves as a temporary storage area for data and is continually updated.

thrashing

In computer science, thrashing occurs when a computer's virtual memory subsystem is in a constant state of paging, rapidly exchanging data in memory for data on disk, to the exclusion of most application-level processing.

nonvolatile memory

Non-volatile memory is typically used for the task of secondary storage, or long-term persistent storage. The most widely used form of primary storage today is a volatile form of random access memory (RAM), meaning that when the computer is shut down, anything contained in RAM is lost.

read-only memory (ROM)

Once data has been written onto a ROM chip, it cannot be removed and can only be read. Unlike main memory (RAM), ROM retains its contents even when the computer is turned off. ROM is referred to as being nonvolatile, whereas RAM is volatile.

gigahertz (GHz)

One GHz represents 1 billion cycles per second. The speed of microprocessors, called the clock speed, often is measured in gigahertz.

machine cycle

The basic operation performed by a central processing unit (CPU). A CPU is the main logic unit of a computer.

instruction cycle (I-cycle)

The basic operational process of a computer. It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction dictates, and carries out those actions.

central processing unit (CPU)

The brains of the computer where most calculations take place.

control unit

The control unit (CU) is a component of a computer's central processing unit (CPU) that directs operation of the processor. It tells the computer's memory, arithmetic/logic unit and input and output devices how to respond to a program's instructions.

multicore processor

Two or more CPUs working together on the same chip. Also called multicore technology, it is a type of architecture where a single physical processor contains the core logic of two or more processors.

volatile memory

Volatile memory is computer storage that only maintains its data while the device is powered. Most RAM (random access memory) used for primary storage in personal computers is volatile memory.

megahertz (MHz)

one million hertz, especially as a measure of the frequency of radio transmissions or the clock speed of a computer.