Before delving into the history of computers, it helps to be familiar with the components of modern ones.
A computer consists of hardware and software. Hardware is the part of the computer that can be kicked. Software is the part of the computer that lies behind the screen that deserves the kicking it can never get.
Software is code that does data processing of every sort. Code comprises programmed instructions that a computer’s processor understands. Firmware is software that interfaces to hardware devices.
The overarching software that provides the platform for application programs is an operating system (OS). An OS manages all basic computer operations, including peripheral-device firmware and file storage. Modern operating systems also provide common services for application programs, which are the software widgets that users fiddle with.Hard
The hardware heart of every computer is a central processing unit (CPU). The CPU is ensconced on a single semiconductor chip called a microprocessor.
The CPU chip is clamped into a socket on a motherboard, which is a printed circuit board (PCB) that is thoroughly etched with connections among various components.
A CPU employs random-access memory (RAM) for storing programs and data. RAM chips are soldered onto PCB sticks which are stuck in slots that connect the memory to the motherboard.
RAM remembers only when power is on. The contents of this memory are lost when the power is switched off.
Memory is measured in bytes. A byte is 8 binary bits. The decimal capacity of a byte is 256 (0–255).
A kilobyte (properly kB; typically, kb or KB, or simply k) is 210 (1,024) bytes; nowadays used loosely for 1,000. A megabyte (MB) is 220 (1,048,576) bytes (= 1,0242).
A gigabyte (GB) is 230 (1,073,741,824) bytes (= 1,0243). Storage drive manufacturers cheat and call a GB a billion bytes (1,000,000,000).
A computer has lasting storage in the form of drives, the most common being disc drives, which are spinning platters in a case. The platters store data electromagnetically.
There are also solid-state drives (SSD), which have no moving parts, as an SSD comprises a memory IC (integrated circuit) chip. The most common form of SSD is the thumb drive (aka flash drive or USB drive) which are small sticks of retentive memory which easily fit into pockets and crawl into hidden places.
Data skitter around a motherboard on electrical pathways that comprise a communication system called a bus. The bus connects the CPU to RAM and all other components that connect to the motherboard, including external devices, such as a keyboard or USB drives.
USB is the acronym for Universal Serial Bus. USB is a specific protocol for transferring and translating bits of data to and from external devices serially so that they can be understood by the CPU.
The protocol for buses may involve transferring data serially (sequentially, bit by bit) or in parallel (multiple bits: that is, word by word). Serial may seem slower, but serial links can be clocked much faster than parallel ones, and serial transfer is inherently more reliable, because the circuitry for handling serial transmission is simpler.
Unlike disc drives and SSDs, which can interactively store new data, optical discs, such as CDs (compact discs) and DVDs (digital video discs), store preformatted data.
Writing to an optical disc is called burning. Copying from an optical disc is called ripping. The term ripping is especially used when the material on the disc is copyrighted, because it feels that way.
Computer input devices include keyboards and hardware which indicates a location on a bitmapped display, such as mice and trackballs. A finger becomes an input device on touch-sensitive screens.
A computer display is also called a screen or monitor. Bitmapped means that each dot (pixel) on a display is independently accessible. On the early black-and-white displays, a pixel could be mapped to a single bit in memory: 0 for black, 1 for light; hence the term bitmap. On grayscale or color screens multiple bits are needed for each dot. But the term bitmapped is still used.
A display is an output device. Printers are another common output device. A scanner is an analogous input device to a printer in reading in a page of data at a time.
A sophisticated conception of computing was realized by 100 bce with an analog computer designed to predict astronomical positions and eclipses. The Antikythera mechanism was a complex clockwork device comprising at least 30 meshing bronze gears; named after the Greek island where it was found in an ancient shipwreck. Such technology was lost at some point in antiquity, with its equivalence not appearing again until the advent of mechanical astronomical clocks in 14th-century Europe.
Getting to the point of being able to process data in a generalized fashion, as opposed to some specific calculation, took most of the history of hardware: nearly 5 millennia. Only in the 1950s, with the advent of IC chips, did computers evolve into general data-processing machines. After that, the advance of computer hardware has been a process of miniaturization.
We begin our survey of computing hardware at the time when fingers were the input device, as they have become again on the handheld electronic tablets which are now so ubiquitous.