1.6 Computer Tour

Clock

A processor's instructions execute at a rate governed by the processor's clock, which ticks at a specific frequency. Processors have clocks that tick at rates such as 1 MHz (1 million ticks/second) for an inexpensive processor ($1) like those found in a microwave oven or washing machine, to 1 GHz (1 billion ticks/second) for costlier ($10-$100) processors like those found in mobile phones and desktop computers. Executing about 1 instruction per clock tick, processors thus execute millions or billions of instructions per second.

RAM goes through:

CPU

Relatively small volatile storage with fastest access, which is located on the processor chip is called ______

Cache

Storage

A DISK (aka hard drive) stores files and other data, such as program files, song/movie files, or office documents. Disks are non-volatile, meaning they maintain their contents even when powered off. They do so by orienting magnetic particles in a 0 or 1 position. The disk spins under a head that pulses electricity at just the right times to orient specific particles (you can sometimes hear the disk spin and the head clicking as the head moves). New flash storage devices store 0s and 1s in a non-volatile memory, rather than disk by tunneling electrons into special circuits on the memory's chip and removing them with a "flash" of electricity that draws the electrons back out.

Input/output devices

A SCREEN (or monitor) displays items to a user. The above examples displayed textual items, but today's computers display graphical items, too. A KEYBOARD allows a user to provide input to the computer, typically accompanied by a mouse for graphical displays. Keyboards and mice are increasingly being replaced by touchscreens. Other devices provide additional input and output means, such as microphones, speakers, printers, and USB interfaces. I/O devices are commonly called peripherals.

RATE at which a processor executes instructions.

Clock

Nonvolatile storage with slower access

Disk

What manages programs and interfaces with peripherals?

Operating System

A common way to make a PC faster is to add more what?

RAM

A computer needs ______ to get to the CPU

RAM

______ is volatile storage with faster access, usually located off processor chip.

RAM

Memory

RAM (random-access memory) temporarily holds data read from storage and is designed such that any address can be accessed much faster than disk, in just a few clock ticks (see below) rather than hundreds of ticks. The "random access" term comes from being able to access any memory location quickly and in arbitrary order, without having to spin a disk to get a proper location under a head. RAM is costlier per bit than disk, due to RAM's higher speed. RAM chips typically appear on a printed-circuit board along with a processor chip. RAM is volatile, losing its contents when powered off. Memory size is typically listed in bits or in bytes, where a BYTE is 8 bits. Common sizes involve megabytes (million bytes), gigabytes (billion bytes), or terabytes (trillion bytes).

Processor

The PROCESSOR runs the computer's programs, reading and executing instructions from memory, performing operations, and reading/writing data from/to memory. When powered on, the processor starts executing the program whose first instruction is (typically) at memory location 0. That program is commonly called the BIOS (basic input/output system), which sets up the computer's basic peripherals. The processor then begins executing a program called an OPERATING SYSTEM (OS). The operating system allows a user to run other programs and interfaces with the many other peripherals. Processors are also called CPUs (central processing units) or microprocessors (a term introduced when processors began fitting on a single chip, the "micro-" suggesting something small). Because speed is so important, a processor may contain a small amount of RAM on its own chip, called CACHE memory, accessible in one clock tick rather than several, for maintaining a copy of the most-used instructions/data.

Moore's Law is:

The doubling of IC capacity roughly every 18 months.

A processor spends much of its time moving instructions/data between memory and storage, because not all of a program's instructions/data may fit in memory. Is this one of the reasons that a PC would be running slow?

Yes

The OS runs ProgB. The disk spins and the head loads ProgB from the disk, storing the contents into what?

memory

A disk is able to store ____________ of data and may contain various programs such as ProgA, ProgB, Doc1, Doc2, and OS. The memory is able to store Gigabytes of data. User runs ProgA. The disk spins and the head loads ProgA from the disk, storing the contents into memory.

terabytes

What was Moore's Law?

the doubling of IC capacity roughly every 18 months, which continued for several decades.