1.2 Hardware and Software
Computers can perform calculations and make logical decisions phenomenally faster than human beings can. Many of today’s personal computers can perform billions of calculations in one second—more than a human can perform in a lifetime. Supercomputers are already performing thousands of trillions (quadrillions) of instructions per second! IBM has developed the IBM Summit supercomputer, which can perform over 122 quadrillion calculations per second (122 petaflops)!2 To put that in perspective, the IBM Summit supercomputer can perform in one second almost 16 million calculations for every person on the planet!3 And supercomputing upper limits are growing quickly.
Computers process data under the control of sequences of instructions called computer programs (or simply programs). These software programs guide the computer through ordered actions specified by people called computer programmers.
A computer consists of various physical devices referred to as hardware (such as the keyboard, screen, mouse, solid-state disks, hard disks, memory, DVD drives and processing units). Computing costs are dropping dramatically, due to rapid developments in hardware and software technologies. Computers that might have filled large rooms and cost millions of dollars decades ago are now inscribed on computer chips smaller than a fingernail, costing perhaps a few dollars each. Ironically, silicon is one of the most abundant materials on Earth—it’s an ingredient in common sand. Silicon-chip technology has made computing so economical that computers have become a commodity.
1.2.1 Moore’s Law
Every year, you probably expect to pay at least a little more for most products and services. The opposite has been the case in the computer and communications fields, especially with regard to the hardware supporting these technologies. For many decades, hardware costs have fallen rapidly.
Every year or two, the capacities of computers have approximately doubled inexpensively. This remarkable trend often is called Moore’s Law, named for the person who identified it in the 1960s, Gordon Moore, co-founder of Intel—one of the leading manufacturers of the processors in today’s computers and embedded systems. Moore’s Law and related observations apply especially to
the amount of memory that computers have for programs,
the amount of secondary storage (such as solid-state drive storage) they have to hold programs and data over longer periods of time, and
their processor speeds—the speeds at which they execute their programs (that is, do their work).
Similar growth has occurred in the communications field—costs have plummeted as enormous demand for communications bandwidth (that is, information-carrying capacity) has attracted intense competition. We know of no other fields in which technology improves so quickly and costs fall so rapidly. Such phenomenal improvement is truly fostering the Information Revolution.
1.2.2 Computer Organization
Regardless of differences in physical appearance, computers can be envisioned as divided into various logical units or sections:
Input Unit
This “receiving” section obtains information (data and computer programs) from input devices and places it at the disposal of the other units for processing. Most user input is entered into computers through keyboards, touch screens and mouse devices. Other forms of input include receiving voice commands, scanning images and barcodes, reading from secondary storage devices (such as hard drives, Blu-ray Disc™ drives and USB flash drives—also called “thumb drives” or “memory sticks”), receiving video from a webcam and having your computer receive information from the Internet (such as when you stream videos from YouTube® or download e-books from Amazon). Newer forms of input include position data from a GPS device, motion and orientation information from an accelerometer (a device that responds to up/down, left/right and forward/backward acceleration) in a smartphone or wireless game controller (such as those for Microsoft® Xbox®, Nintendo Switch™ and Sony® PlayStation®) and voice input from intelligent assistants like Apple Siri®, Amazon Echo® and Google Home®.
Output Unit
This “shipping” section takes information the computer has processed and places it on various output devices to make it available for use outside the computer. Most information that’s output from computers today is displayed on screens (including touch screens), printed on paper (“going green” discourages this), played as audio or video on smartphones, tablets, PCs and giant screens in sports stadiums, transmitted over the Internet or used to control other devices, such as self-driving cars, robots and “intelligent” appliances. Information is also commonly output to secondary storage devices, such as solid-state drives (SSDs), hard drives, DVD drives and USB flash drives. Popular recent forms of output are smartphone and game-controller vibration, virtual reality devices like Oculus Rift®, Sony® PlayStation® VR and Google Daydream View™ and Samsung Gear VR®, and mixed reality devices like Magic Leap® One and Microsoft HoloLens™.
Memory Unit
This rapid-access, relatively low-capacity “warehouse” section retains information that has been entered through the input unit, making it immediately available for processing when needed. The memory unit also retains processed information until it can be placed on output devices by the output unit. Information in the memory unit is volatile—it’s typically lost when the computer’s power is turned off. The memory unit is often called either memory, primary memory or RAM (Random Access Memory). Main memories on desktop and notebook computers contain as much as 128 GB of RAM, though 8 to 16 GB is most common. GB stands for gigabytes; a gigabyte is approximately one billion bytes. A byte is eight bits. A bit is either a 0 or a 1.
Arithmetic and Logic Unit (ALU)
This “manufacturing” section performs calculations, such as addition, subtraction, multiplication and division. It also contains the decision mechanisms that allow the computer, for example, to compare two items from the memory unit to determine whether they’re equal. In today’s systems, the ALU is part of the next logical unit, the CPU.
Central Processing Unit (CPU)
This “administrative” section coordinates and supervises the operation of the other sections. The CPU tells the input unit when information should be read into the memory unit, tells the ALU when information from the memory unit should be used in calculations and tells the output unit when to send information from the memory unit to specific output devices. Most computers have multicore processors that implement multiple processors on a single integrated-circuit chip. Such processors can perform many operations simultaneously. A dual-core processor has two CPUs, a quad-core processor has four and an octa-core processor has eight. Intel has some processors with up to 72 cores. Today’s desktop computers have processors that can execute billions of instructions per second.
Secondary Storage Unit
This is the long-term, high-capacity “warehousing” section. Programs or data not actively being used by the other units normally are placed on secondary storage devices (e.g., your hard drive) until they’re again needed, possibly hours, days, months or even years later. Information on secondary storage devices is persistent—it’s preserved even when the computer’s power is turned off. Secondary storage information takes much longer to access than information in primary memory, but its cost per unit is much less. Examples of secondary storage devices include solid-state drives (SSDs), hard drives, read/write Blu-ray drives and USB flash drives. Many current drives hold terabytes (TB) of data—a terabyte is approximately one trillion bytes). Typical hard drives on desktop and notebook computers hold up to 4 TB, and some recent desktop-computer hard drives hold up to 15 TB.4
Self Check for Section 1.2
(Fill-In) Every year or two, the capacities of computers have approximately doubled inexpensively. This remarkable trend often is called .
Answer: Moore’s Law.(True/False) Information in the memory unit is persistent—it’s preserved even when the computer’s power is turned off
Answer: False. Information in the memory unit is volatile—it’s typically lost when the computer’s power is turned off.(Fill-In) Most computers have processors that implement multiple processors on a single integrated-circuit chip. Such processors can perform many operations simultaneously.
Answer: multicore.