Parts of a Computer System

Hardware

The main parts of a computer system hardware consists of the CPU and all peripheral devices, that is those pieces of equipment attached to the CPU.

CPU

CPU (Central Processing Unit)
Sometimes this term is used to refer to entire computer "box". Other times it refers to just the microprocessor chip mounted on the motherboard inside.

Input Devices
These are any peripheral devices that provide data input to the CPU. This includes but is not limited to things like:

Keyboard
Mouse
Joystick
Output Devices
These are any peripheral devices that provide data output from the CPU. This includes but is not limited to things like:

Monitor
Printer
Mass Storage Devices
These are any peripheral devices that provide data storage for the CPU. These devices are both input and output devices. This includes but is not limited to things like:

Hard Drive (internal or external)
CD/DVD Drive
Thumb/Jump Drive

Motherboard

This the main circuit board in the CPU. It contains the microprocessor which is the heart of the computer. Some computer engineers refer to anything (even if it is mounted to the motherboard) that is connected external to the microprocessor as a peripheral device. The motherboard has connection slots on it for the external storage devices (hard drive, CD/DVD drive) as well as connections for any USB devices like a thumb drive. It also has connections for a video card to control display sent to the monitor and a number of PCI slots for miscellaneous peripheral devices. One very import chip mounted on the motherboard is the clock chip. This keeps everything synchronized. The speed of the clock is measured in nanoseconds or clock cycles per second, that is billionths of a second. To get an idea of just how brief a nanosecond is consider this. One nanosecond is to one second what one second is to approximately 31 years, 8 months, and 2 weeks.

Mounted on the motherboard you will also find the memory chips. These usually consist of several integrated circuit chips mounted on a printed circuit board which is plugged into a slot on the motherboard. The memory chips are of two types. The first if Read Only Memory. This is the part of the computers memory where certain programs responsible for running the computer are permanently stored. As the name implies the data in these chips is read only. Then there is Random Access Memory. These are chips where the operating system, system support software, and programs you are running are stored. This is dynamic memory which can be changed while the computer is running.

Microprocessor

Internal layout of one version of the Intel microprocessor

The microprocessor is an incredibly complex integrated circuit consisting of thousands of transistors, resisters, capacitors, and other electronic components all on a sliver of purified silicon little more than one-half inch square. It consists of a number of separate sections:

Arithmetic-Logic Unit (ALU) - Mathematical and logical calculations are performed in this section.
Microcode - Stores, and retrieves the code which executes individual assembly language instructions. This is, in essence, the programming language (microcode) that interprets the programming language (machine language) that interprets the assembly language code that interprets your C++ code.
Instruction decode unit - Translates the machine language code into microcode.
Various registers - Internal memory locations used as temporary storage while executing microcode.
Accumulator - The main working register used by the ALU.
Memory interface - Interface to the ROM and RAM.

Evolution of the Microprocessor

There are a number of manufacturing companies producing microprocessor chips. The image below will give you an idea of just how far and fast the evolution of the microprocessor has come. The early microprocessors could only access 64 kilobytes of memory. The newer processors can now access over one terabyte (that's approxiimately 1,099,511,627,776 bytes which is 16,777,216 times as much memory as could be accessed by the 1971 microprocessors).

The 1971 microprocessor ran at a clock speed of approximately 1/4 of a Megahertz and contained around 2,300 transisters. By the mid 1990s they ran at clock speeds of up to 1 or 2 Gigahertz and contain over 5 million transistors.

Moore's Law Microprocessor development tends to follow Moore’s Law. Named for Intel co-founder Gordon E. Moore. It came from an article he published in Electronics Magazine, April 19, 1965. Basically it states:

The complexity for minimum component costs has increased at a rate of roughly a factor of two per year... Certainly over the short term this rate can be expected to continue, if not to increase. Over the longer term, the rate of increase is a bit more uncertain, although there is no reason to believe it will not remain nearly constant for at least 10 years. That means by 1975, the number of components per integrated circuit for minimum cost will be 65,000. I believe that such a large circuit can be built on a single wafer.

Moore's law also tends to apply to processing speed, memory capacity, and even the number of pixels in a digital camera image.

Gordon E. Moore
Co-founder of Intel Corporation

Graph of Moore's Law

In the mid-1990s a new technology for microprocessor development appeared known as Multi-Core Technology. This involved creating microprocessor chips that were, in fact, several microprocessors on a single chip, each of which could be running different programs or multiple threads in a single program. In 2005, the first personal computer dual-core processors were announced and as of 2009 dual-core and quad-core processors were widely used in servers, workstations and PCs while six and eight-core processors will be available for high-end applications in both the home and professional environments. Sun Microsystems has released the Niagara and Niagara 2 chips, both of which feature an eight-core design. The Niagara 2 supports more threads and operates at 1.6 GHz.

Intel 8-Core Niagara Microprocessor

Software

Any program that is loaded into RAM or ROM memory that can be executed by the microprocessor is called software. All of ROM contains programs which handle the input and output of the computer and basic parts of the operating system. RAM is used for most of the operating system, numerous utility programs which run in the background, and all of the programs which you load and run.

Memory

The computer’s memory divided up into two sections: ROM or Read Only Memory and RAM or Random Acess Memory. This was discussed above. Both RAM and ROM are made up of many thousands or millions (and soon to be billions) of units called Bytes. You may be familiar with the terms Kilobyte (Kb - 1024 bytes), Megabyte (Mb - 1024Kb, 1,048,576 bytes) and Gigabyte (Gb - 1024 Mb, 1,073,741,824 bytes).

Each byte consists of eight bits. Each bit is like a simple on/off switch. With eight switches you can have up to 256 different combinations of on and off. This is the way data is encoded in the computer.